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Detailed explanations in West Bengal Board Class 9 Life Science Book Solutions Chapter 3.5 Excretion offer valuable context and analysis.

WBBSE Class 9 Science Chapter 3.5 Question Answer – Excretion

Very Short Questions and Answers : (1 mark for each question)

Question 1.
Name a tree, which removes excretory materials by exfoliation of bark.
Answer:
Guava tree removes excretory materials by exfoliation of bark.

Question 2.
Name a plant, which stores most of its excretory matters in leaves.
Answer:
Tea plant stores most of its excretory matters (tannin, theine) in leaves.

Question 3.
Which type of plant excretory substance is disposed through skin of orange?
Answer:
Volatile oil or essential oil is disposed through skin of orange.

Question 4.
What is clove oil?
Answer:
Clove oil is an essential oil excreted by cloves.

Question 5.
Name a medicinally important plant, which disposes its excretory matters through bark.
Answer:
Arjun (Terminalia arjuna) tree disposes its excretory matters through bark.

Question 6.
Which economically important material is excreted from Hevea brasiliensis?
Answer:
Latex of Hevea brasiliensis is the economically important excretory material used to prepare commercial rubber.

Question 7.
Name the plant, whose latex is taken as a supplement of milk.
Answer:
Latex of Brosimum galactodendron is taken as a supplement of milk by the people of Venezuela.

Question 8.
Name a water-soluble non-nitrogenous excretory material of plant.
Answer:
Gum is a water-soluble non-nitrogenous excretory material of plant.

Question 9.
Which part of Rauvolfia plant is the source of reserpine?
Answer:
Root of Rauvolfia plant is the source of reserpine.

Question 10.
From which part of cinchona plant is quinine extracted?
Answer:
Quinine is extracted from the bark of cinchona plant.

Question 11.
What is the source of atropine?
Answer:
Leaves and roots of Atropa belladonna are the sources of atropine.

Question 12.
Which type of plant excretory matters are insoluble in water but most have great medicinal importance?
Answer:
Alkaloids are insoluble in water but most have great medicinal importance.

Question 13.
Name the plant whose excretory material is used for preparing varnish.
Answer:
Excretory material of pine tree is used for preparing varnish.

Question 14.
Name an edible plant excretory matter.
Answer:
Camphor is an edible plant excretory matter.

Question 15.
Name a plant excretory matter used as a common nerve stimulant.
Answer:
Caffeine is used as a common nerve stimulant.

Question 16.
Which alkaloid is used to control hypertension?
Answer:
Reserpine is used to control hypertension.

Question 17.
Name the excretory organ of Amoeba.
Answer:
Contractile vacuole is the excretory organ of Amoeba.

Question 18.
Which is the excretory organ of annelids?
Answer:
Nephridia is the excretory organ of annelids.

Question 19.
From where do malpighian tubules collect excretory materials?
Answer:
Malpighian tubules collect excretory materials from haemolymph.

Question 20.
What is the excretory organ of prawn called?
Answer:
The excretory organ of prawn is called green gland or antennary gland.

Question 21.
What is the structural and functional unit of kidney called?
Answer:
The structural and functional unit of kidney is called nephron.

Question 22.
Which is the site of ultrafiltration in a nephron?
Answer:
Malpighian corpuscle is the site of ultrafiltration in a nephron.

Question 23.
Which portion of human excretory system stores urine for sometime inside the body?
Answer:
Urinary bladder stores urine for sometime inside the body.

Question 24.
In which organ of vertebrate animals is urine prepared?
Answer:
Urine is prepared in the kidneys of vertebrates.

Question 25.
Which branch of artery forms the glomerulus?
Answer:
Afferent renal arteriole forms the glomerulus.

Question 26.
Which arteriole comes out from the glomerulus of nephron?
Answer:
Efferent renal arteriole comes out from the glomerulus of nephron.

Question 27.
Which region of kidney possesses more number of nephrons?
Answer:
Cortical region of kidney possesses more number of nephrons.

Question 28.
Name two materials which are reabsorbed in blood from renal tubule.
Answer:
Amino acids and glucose are two materials reabsorbed in blood from renal tubule.

Question 29.
Name a vitamin which is reabsorbed from glomerular filtrate to blood.
Answer:
Vitamin C is reabsorbed from glomerular filtrate to blood.

Question 30.
Name a hormone, which controls the reabsorption of water from renal tubule.
Answer:
Antidiuretic hormone or ADH controls the reabsorption of water from renal tubule.

Question 31.
Name an excretory material, which is disposed through faeces.
Answer:
Bilirubin is excreted through faeces.

Question 32.
Which main excretory material is eliminated through lungs?
Answer:
Carbon dioxide is the main excretory material, eliminated through lungs.

Question 33.
Through which glands are the fatty excretory materials eliminated from human body?
Answer:
The fatty excretory materials of human body are eliminated through sebaceous glands of the skin.

Question 34.
How much glomerular filtrate is produced in the two kidneys of a healthy adult individual in 24 hours?
Answer:
In 24 hours, about 170 L of glomerular filtrate is produced in the two kidneys of a healthy adult individual.

Question 35.
How much urine is excreted by a healthy adult individual in 2 4 hours?
Answer:
In 24 hours, a healthy adult individual excretes about 1.5 L of urine.

Short Questions and Answers : (2 marks for each question)

Question 1.
What is meant by excretion?
Answer:
Excretion is the process by which harmful metabolic waste products are eliminated from the body of an organism in order to keep it fit and healthy.

Question 2.
Why is excretion treated as a catabolic reaction?
Answer:
By the process of excretion, different metabolic waste matters are eliminated from the body of an organism. This process reduces the dry weight of the organism. Therefore, excretion is treated as a catabolic process.

Question 3.
What is gum?
Answer:
The highly viscous, non-nitrogenous, watersoluble, carbohydrate-rich plant excretory material, produced within the plant body by conversion of cellulose, is called gum.

Question 4.
What are resins?
Answer:
Resins are solid, amorphous or semi-solid, inflammable plant excretory material, which are usually transparent or translucent and yellowish to brown in colour and are soluble in organic solvents (as ether) but not in water. Resins are secreted from injured parts of plants like pine, sal etc.

Question 5.
What are volatile oils or essential oils?
Answer:
Volatile oils or essential oils are quickly evaporating plant excretory materials having a typical odour. Volatile oils are stored in the leaves of lemon, eucalyptus, citronella, etc. and fruits of lemon, orange, etc.

Question 6.
What are alkaloids?
Answer:
Alkaloids are generally colourless, complex nitrogenous organic bases with bitter taste, occuring especially in flowering plants. Example-Morphine, quinine, reserpine etc.

Question 7.
What is latex?
Answer:
A thick, milky white fluid, excreted by many flowering plants (angiosperms), composed of a complex emulsion of proteins, alkaloids, starches, sugars, oils, tannins, resins and gums which coagulate on exposure to air, is called latex. Example-Para-rubber (Hevea brasiliensis), rubber (Ficus elastica), banyan (Ficus benghalensis), different cacti etc.

Question 8.
Mention the sourse and medicinal importance of reserpine.
Answer:
Source: Root extract of Rauvolfia serpentina or ‘sarpagandha’ plant.
Medicinal importance:

1. It is used to control hypertension.
2. Reserpine is a good nerve soother.
3. It is a good medicine for insomnia.

Question 9.
Mention the source and medicinal importance of morphine.
Answer:
Source: Fruit coat of Papaver somniferum or poppy plant.
Medicinal importance:
1. Morphine is used to treat severe pain.
2. It is a strong sedative.

Question 10.
Mention the source and medicinal importance of quinine.
Answer:
Source: Bark of cinchona plant.
Medicinal importance:
1. it is used to treat malaria.
2. It is a good medicine for intestinal disorder.

Question 11.
Mention the source and medicinal importance of caffeine.
Answer:
Source: Seeds of Coffea arabica or coffee plant.
Medicinal importance:
1. It is a good nerve stimulant.
2. It is a moderate pain killer.

Question 12.
Mention the source and medicinal impertance of daturine.
Answer:
Source: Seeds of Datura stramonium or ‘dhutura’ plant.
Medicinal importance:
1. It is used as a medicine for asthma.
2. It is used to prepare narcotic drug.

Question 13.
Mention the source and medicinal importance of atropine.
Answer:
Source: Leaves and roots of Atropa belladonna.
Medicinal importance:
1. It is used to dilate the pupil before ophthalmological investigation.
2. It also used to treat certain inflammatory conditions of the eye.

Question 14.
Mention the source and medicinal importance of theine.
Answer:
Source: Leaves of tea plant.
Medicinal importance: It is consumed as a mild nerve stimulant.

Question 15.
What is tannin? What are its sources?
Answer:
Tannin: Tannin is a bitter tasting carbon-rich material excreted by plants.
Sources of tannin: Tea leaves, haritaki and bohera fruits, stems of Acacia catechu etc.

Question 16.
Mention the source and medicinal importance of azadirachtin.
Answer:
Source: Leaves, stems and fruits of Azadirachta indica or neem plant.
Medicinal importance:
1. It is used as a good medicine to treat various skin problems.
2. It is also used as an effective pesticide.

Question 17.
Mention the source and medicinal importance of strychnine.
Answer:
Source: Seeds of Strychnos nux-vomica.
Medicinal importance: It is used as homeopathic medicine to treat digestive enzyme.

Question 18.
Mention the economic importance of gum.
Answer:
The economic importances of gum are as follows-

1. Gum is used as glue in book-binding industry.
2. It is used as a fixative of lime-based paints, inks and water-based paints.
3. Gums of some plants are used to prepare chocolates.

Question 19
Mention the economic importance of latex.
Answer:
The economic importances of latex are as follows-

1. Latex of rubber plants is the raw material used in industrial rubber, which is used to prepare all rubber material starting from vehicle tyres to pencil erasers.
2. Latex of papaya plant is a source of the protein-digesting enzymepapaine.
3. Latex of Brosimum galactodendron is consumed as a supplement of milk.

Question 20.
Mention the economic importance of resin.
Answer:
The economic importances of resin are as follows-

1. Hard resin is used as a sealing material.
2. Liquid resin is used to prepare turpentine oil.
3. Asafoetida is used as an essence for cuisines.
4. Resin of sal is used to as ‘dhuna’.

Question 21.
Mention the economic importance of tannin.
Answer:
The economic importances of tannin are as follows-

1. It is used in tannery to tan leather.
2. Tannin is used to prepare certain type of ink.
3. It is used as ‘kattha’ or ‘khair’ in betel leaf.

Question 22.
How do unicellular organisms perform excretion?
Answer:
Unicellular organisms like Amoeba, Paramoecium, Euglena etc. carry out excretion with the help of contractile vacuoles. In this process, excess water from cytoplasm enters into a small vacuole. Gradually, it swells and moves towards the periphery. Finally, it bursts and expels water and dissolved waste materials outside the body.

Question 23.
Mention the economic importance of essential oil or volatile oil.
Answer:
The economic importances of essential oil are as follows-

1. It is used to prepare essence for soap, body or hair oil and several other cosmetic items.
2. Essential oil is used to add flavour to different preparations of sweets.
3. Essential oil obtained from eucalyptus is used in pain balms.

Question 24.
How does excretion help in maintaining water balance in a living body?
Answer:
Due to the deposition of waste matters, osmotic pressure in cells changes. As a result, more water enters into the cells, that hampers their normal biological processes. By excretion, waste matters are eliminated from the cells along with water. Thus, excretion helps to maintain water balance and osmotic pressure within cells and tissues of a living body.

Question 25.
How are the metabolic wastes of plants eliminated?
Answer:
In plants, some metabolic wastes are stored in specialised cells or tissues, that are eliminated during any physical injury. Some other excretory matters are deposited in organs like leaves, fruits, barks, which plants shed naturally.

Question 26.
How do animals dispose excretory matter?
Answer:
In animals, toxic excretory products are transported from tissues to specific excretory organs by circulatory system. From these organs, metabolic wastes are eliminated from the body.

Question 27.
How do flame cells work as excretory organ?
Answer:
In animals like tapeworm, liver fluke, etc, the main excretory tube spreads fine branches inside the body, called excretory tubule. Free end of each excretory tubule bears a flame cell, with a tuft of long cilia. These cells collect metabolic wastes and release those matters in the excretory tubule. The entire excretory matters, from all those tubules, reach the main excretory duct and are disposed finally through excretory pore.

Question 28.
Mention the role of nephridium in excretion.
Answer:
Nephridium is the excretory organ of annelids, such as earthworm, leech, etc. Each nephridium (piural nephridia) has three portionsnephritides, tubule and nephridiopore. Nephrostome is a ciliated funnel-shaped end of nephridium, which collects metabolic wastes from coelomic fluid. The coiled tubule collects excretory substances from surrounding blood capillaries.
All these materials are then released outside through nephridiopore, present on the skin.

Question 29.
How do malpighian tubules work as an excretory organ of insects?
Answer:
Malpighian tubules are present as a tuft of very fine tubules, at the junction of mid-gut and hind-gut of insects. These tubules absorb nitrogenous waste matters from haemolymph (insect blood) and dispose it inside the alimentary canal. Finally, the excretory products are eliminated along with faeces of insects.

Question 30.
Distinguish between latex and alkaloid.
Answer:

Features	Latex	Alkatoid
1. General nature	Milky white fluid	Colourless, faintly yellow to dark brown, non-secretory matter
2. Chemical nature	Non-nitrogenous	Nitrogenous
3. Medicinal importance	Insignificant	High medicinal value

Question 31.
Distinguish between maipighian corpuscle and malpighian tubule.
Answer:

Features	Malpighian copuscle	Malpighian tubule
1. Occurence	At the free end of nephron of all vertebrates	At the junction of mid-gut and hind-gut of insects
2. Structure	Knob-like corpuscular structure	Fine tubular structures
3. Components	Glomerulus and Bowman’s capsule	Only a close-ended tubular structure
4. Function	Ultrafiltration of blood	Absorption of excretory matters from haemolymph

Long Questions and Answers : (5 marks for each question)

Question 1.
What is the significance of excretion?
Answer:
Significance of excretion
Excretion is an important physiological process which helps to lead a healthy life. Its significance is discussed below.
1. Maintenance of fit and healthy life: Excretion removes all toxic and harmful matters produced in the cells by various metabolic activities.
2. Maintenance of water balance: Excretion removes excess water from the cells to maintain water balance in the body.
3. Recycling of matters: By excretion, many elements, present in the waste materials, are disposed in nature. These are made available for reuse by action of decomposers.
4. Economic importance: Many plant excretory products, especially alkaloids, have certain medicinal importance. Gums, resins, tannins, latex etc. are used for industrial purposes. Some nitrogen-rich animal excretory products are used as fertilisers.

Question 2.
How do plants dispose excretory materials?
Answer:
Excretion in plants
Plants eliminate excretory products by the following processes.
1. Shedding of leaves: Trees, such as hog palm, Albizia, silk cotton etc. store excretory substances in leaves. These trees shed leaves once a year to dispose those excretory substances.

2. Exfoliation of barks: Some trees, such as guava, arjun etc. deposit waste matters in their bark. These plants naturally peel off their bark to eliminate those waste matters from time to time.

3. Shedding of fruits: Plants like lemon, apple, tamarind etc. store excretory matters, like different organic acids (eg, citric acid, tartaric acid, malic acid, etc.) or essential oils in their fruits. These matters are removed from these plants by shedding of fruits.

4. Shedding of flowers: In some plants, excretory products are stored in their flowers. These products are excreted when different parts of the flowers are shedded off. Example-Clove flower.

5. Aikaloids: Sometimes alkaloids are stored in the stems and leaves of some plants like banyan, Calotropis etc. In alkaloids different types of excretory products remain solubilised. In case of injury, these alkaloids are released outside and in this way other soluble excretory products are also relaeased.

6. Resin secretion: In the resin ducts of stem and leaves of some plants, like pine, a complex insoluble excretory product called resin is present.

7. Gum excretion: In some plants such as babul, soluble wastes are excreted in the form of gum.

8. Excretion of water: Potato, tomato etc. solubilise different excretory products in water and then excrete them with the help of hydathodes.

Question 3.
Name the non-nitrogenous excretory products of plants. Compare them. Non-nitrogenous excretory products of plants
Answer:
The non-nitrogenous excretory products of plants are gum, latex and resin.
Comparison among gum, latex and resin

Question 4.
Distinguish between excretion in plants and animals.
Answer:
Differences between excretion in plants and animals

Features	Plants	Animals
1. Definite excretory organ and excretory system	Absent	Present
2. Amount of excretory products formed	Less	More
3. Nature of excretory products	Simpler and less harmful	More complex and more harmful
4. Fate of excretory products	Mostly stored	Generally excreted from the body and partially stored in some cases
5. Reutilisation of the excretory products	Some excretory products are used in metabolism	Generally not used
6. Nitrogenous excretory product	Less	More
7. Toxicity	Less	More

Question 5.
Briefly describe the structure of human excretory system.
Answer:
Structure of human excretory system
Human excretory system consists of a pair of kidneys, two ureters, a urinary bladder and a urethra.
1. Kidneys: The kidneys are brown coloured, bean-shaped structures, positioned at either side of vertebral column, just below the ribs. The concave face of the kidney is called the pelvis. The section of kidney shows two distinct regions-outer cortex and inner medulla. A renal artery enters and a renal vein leaves each kidney through the pelvis. Numerous fine tubular structures, called nephrons, are present in kidneys, which filters blood from the specially designed renal capillaries.

2. Ureter: Ureters are two in number. Each ureter is a 35 cm long, slightly curved tube, emerging from the renal pelvis. Ureters are usually 2-4 mm in diameter. The ureters connect kidneys to the urinary bladder, present at the lower portion of the abdominal cavity.

3. Urinary bladder and urethra: Urinary bladder is a muscular sac, located at the front lower portion of the abdominal cavity. Urethra is a muscular tube that descends from the floor of the bladder. The base of urethra is equipped with sphincter muscles, which help to hold the urine inside urinary bladder.
Urine enters the urinary bladder via the ureters and leaves via urethra. The capacity of a typical human bladder is 300-500 ml.

Question 6.
Briefly describe the structure of nephron.
Answer:
Structure of nephron
A nephron has two parts-malpighian corpuscles and renal tubule.
1. Malpighian corpuscles: It is situated at the free and blind end of a nephron. This portion is composed of Bowman’s capsule and glomerulus. The free and blind end of nephron forms a cup-shaped double-walled structure, called the Bowman’s capsule. A fine branch of renal artery enters into the Bowman’s capsule as afferent arteriole. It ramifies to form a capillary network inside the capsule, where these capillaries reunite and return as efferent arteriole. It is comparatively narrower than the afferent arteriole. This capillary network is called glomerulus.

2. Renal tubule: It is a convoluted tubule, extending from the base of the Bowman’s capsule and ending in the collecting tubule. Renal tubule has three parts-proximal convoluted tubule, which starts from the base of the Bowman’s capsule; loop of Henle, which is a ‘U’-shaped loop-like structure, and distal convoluted tubule, which ultimately meets a comparatively wider collecting tubule. Several collecting ducts finally unite to form thicker ducts, called the duct of Bellini.

Question 7.
Describe the steps of urine formation in human kioney.
Answer:
Steps of urine formation in human kidney
The mechanism of urine formation in nephron involves four different phases, which are mentioned below.
1. Glomerular ultrafiltration: Due to increased blood pressure in the glomerular capillaries, water from blood plasma enters into Bowman’s capsule. This water carries different excretory materials like urea, uric acid, etc. and many essential substances like glucose, amino acids, smaller protein molecules, salts, ions, vitamins, etc. This process is known as glomerular ultrafiltration and the dilute fluid, collected in the Bowman’s capsule, is called glomerular filtrate.

2. Reabsorption: Glucose and different ions (K⁺, Na⁺. etc.) are reabsorbed in cells of renal tubule from the glomerular filtrate by active transport. Cells of proximal convoluted tubules reabsorb the small protein molecules by phagocytosis. Ions like phosphates, bicarbonates, chlorine, etc., vitamin C, amino acids and many other substances are reabsorbed by renal tubule. All these reabsorbed essential materials then return to the blood.

3. Secretion: Creatine, creatinine, hippuric acid, etc. are some excretory materials, which are secreted from the renal tubule.

4. Passive absorption of water: Excess water from the glomerular filtrate is reabsorbed by passive transport in the loop of Henle and distal convoluted tubule. Reabsorption of water is controlled by a posterior pituitary hormone, named Antidiuretic Hormone (ADH).
After these four steps, normal concentrated urine is formed in nephron, which is received by the collecting tubule and finally reach the duct of Bellini.

Question 8.
Write about the roles of the accessory excretory organs other than the kidney.
Answer:
Roles of excretory organs other than kidney

Detailed explanations in West Bengal Board Class 9 Life Science Book Solutions Chapter 2.3B Tissue: Animal Tissue and its Distribution offer valuable context and analysis.

WBBSE Class 9 Science Chapter 2.3B Question Answer – Tissue: Animal Tissue and its Distribution

Very Short Questions and Answers : (1 mark for each question)

Question 1.
Which tissue has liquid matrix?
Answer:
Blood has liquid matrix.

Question 2.
Which tissue has rigid calcified matrix?
Answer:
Bone tissue has rigid calcified matrix.

Question 3.
Where does connective tissue originate from?
Answer:
Connective tissue originates from mesoderm.

Question 4.
Where does nervous tissue originate from?
Answer:
Nervous tissue originates from ectoderm.

Question 5.
Which tissue is responsible for absorption of nutrients from intestinal tract?
Answer:
Epithelial tissue of intestinal lining is responsible for absorption of nutrients from intestinal tract.

Question 6.
Activity of which tissue or tissues directly controls the batting skill in the game of cricket?
Answer:
Activity of muscular and nervous tissues controls the batting skill in the game of cricket.

Question 7.
Name a type of cell that is present in bones.
Answer:
Osteocyte is a type of cell that is present in bones.

Question 8.
Which tissue plays the major role in circulation of blood through blood vessels?
Answer:
Muscular tissue, especially the cardiac muscles and muscular layer of blood vessels play major roles in circulation of blood through blood vessels.

Question 9.
Which proteins are responsible for muscular contraction?
Answer:
Contractile proteins, namely actin and myosin are responsible for muscular contraction.

Question 10.
Which is the other name of voluntary muscle?
Answer:
The other name of voluntary muscle is skeletal muscle.

Question 11.
Why voluntary muscles are called striated muscles?
Answer:
Under microscope, alternate dark and light striations are seen across the voluntary muscle fibres. Therefore, these are called striated muscles.

Question 12.
Which type of cells is present on the inner lining of the respiratory tract?
Answer:
Epithelial cells are seen on the inner lining of the respiratory tract.

Question 13.
Which type of muscles never get fatigued?
Answer:
Cardiac muscles never get fatigued.

Question 14.
Which tissue helps us to respond to the changes in the environment?
Answer:
Nervous tissue helps us to respond to the changes in environment.

Question 15.
Which are the receiving projections of neurons?
Answer:
Dendrons are the receiving projections of a neuron.

Question 16.
What are muscle fibres?
Answer:
The fine elongated contractile components of muscular tissues are called muscle fibres.

Question 17.
Which type of muscles are branched?
Answer:
Cardiac muscles are branched.

Question 18.
Which is the short and well-branched projection of a neuron?
Answer:
Dendrons is the short and well-branched projections of a neuron.

Question 19.
Name the longer and less branched projection of a nerve cell.
Answer:
Axon is the longer and less branched projection of a nerve cell.

Question 20.
Name the lipid-rich insulating coating present on the axon.
Answer:
The lipid-rich insulating coating present on the axon is known as myelin sheath.

Question 21.
Name the neuron, which does not have any lipid-rich insulating coating on the axon.
Answer:
A neuron without any lipid-rich insulating coating on the axon, is known as nonmyelinated neuron.

Question 22.
Name the specialised nerve cells having lipidrich insulating coating on the axon.
Answer:
The nerve cells, which have lipid-rich insulating coating on the axon, are called myelinated neuron.

Question 23.
Which is the most flexible connective tissue of our body?
Answer:
Cartilage is the most flexible connective tissue of our body.

Question 24.
Which is the most rigid connective tissue of our body?
Answer:
Bone is the most rigid connective tissue of our body.

Question 25.
Name the fluid connective tissues of human body.
Answer:
Blood and lymph are the two fluid connective tissues of human body.

Question 26.
What type of tissue is tendon?
Answer:
Tendon is a connective tissue.

Question 27.
Which two connective tissues are built for bearing weight of the body?
Answer:
Bones and cartilages are the two connective tissues, built for bearing weight of the body.

Short Questions and Answers : (2 marks for each question)

Question 1.
What is meant by epithelial tissue?
Answer:
The tissue, which typically covers the outer surface of the body as well as the inner and outer lining of internal organs, is known as epithelial tissue. It consists of one or more cell-layers.

Question 2.
What is basement membrane? What does it do
Answer:

• Basement membrane: Basement membrane is a typical acellular layer of epithelial tissue, composed of materials, somewhat similar to matrix of connective tissue.
• Functions: Basement membrane holds the epithelial cells on it. It also helps the epithelium to remain attached to the surface of the connective tissue layer below it.

Question 3.
Mention the types of epithelial tissues.
Answer:
There are 3 major types of epithelial tissues. They are-

• simple epithelial tissue
• pseudostratified epithelial tissue and
• stratified epithelial tissue.

Question 4.
Mention the types of simple epithelial tissues.
Answer:
Simple epithelial tissue are of different types. These are-

• squamous epithelium
• cuboidal epithelium
• columnar epithelium
• glandular enithelinm and
• ciliated epithelium.

Question 5.
Mention the distribution of epithelial tissue.
Answer:
Epithelial tissue is present on the outer surface of the body (skin) and the inner lining of oral cavity, intestine, blood vessels, nasal passage, respiratory tracts, alveoli, renal tubules, urinary bladder, uterus, fallopian tube and different glands.

Question 6.
Give two roles of glandular epithelium.
Answer:
Two roles of glandular epithelium are as follows-

• Glandular epithelium present in the inner lining of gastro-intestinal tract secretes various digestive enzymes.
• In endocrine glands, glandular epithelium secretes hormones.

Question 7.
What is meant by cennective tissue?
Answer:
The tissue of mesodermal origin, composed of less cells and more acellular matrix, connecting different tissues is known as connective tissue.

Question 8.
Schematically represent different types of connective tissues.
Answer:
Schematic representation of different types of connective tissue is given below—

Question 9.
What is meant by muscular tissue?
Answer:
The tissue, which has ability to contract and relax and is associated with the movement, is known as muscular tissue.

Question 10.
Mention one function of tendon and ligament each.
Answer:
Function of tendon is to connect muscles to bones. Function of ligament is to connect a bone to another bone.

Question 11.
How many types of muscular tissues are found in higher animals?
Answer:
In higher animals three types of muscular tissues are found, these are-

• voluntary or skeletal muscles,
• smooth muscles and
• cardiac muscles.

Question 12.
Mention the distribution of muscular tissue.
Answer:
The distribution of muscular tissue is as follows-

• Voluntary muscles are attached to bones.
• Smooth involuntary muscles are present in the vital visceral organs, such as oesophagus, intestine, urinary bladder, stomach etc.
• Cardiac muscles are present in the heart.

Question 13.
Write down the functions of different types of muscles.
Answer:
The functions of different muscles are as follows-

• Skeletal muscles help in movement & locomotion.
• Smooth muscles control the movement of the visceral organs like stomach, intestine, urinary bladder, etc.
• Cardiac muscles are responsible for rhythmic contraction and relaxation of heart.

Question 14.
What is nervous tissue?
Answer:
The tissue, which is responsible for receiving and transmitting impulses and thereby coordinating different parts of the body, is known as nervous tissue.

Question 15.
Which are the cellular components of nerve tissue? Where do you find those components?
Answer:

• Cellular components of nerve tissue: Neuron and neuroglia are the two cellular components of the nerve tissue.
• Distribution of neuron and neuroglia: Neurons are present in brain, spinal cord, sense organs and nerves. Several neurons, surrounded by connective tissue, form a nerve. Neuroglia cells are found in brain and spinal cord as packing material of neurons, providing them with necessary support and insulation.

Question 16.
Write the functions of nerve tissue.
Answer:
The functions of nerve tissue are as follows-

• Nerve tissue receives external and internal stimuli and responds to them.
• It carries impulses and makes the body aware of the changes in environment.
• It helps to maintain coordination among all organs within the body.

Question 17.
Why blood is called fluid connective tissue?
Answer:
Blood is mesodermal in origin, has less cells and more matrix, and it maintains connection among various parts of the body. On the other hand, the matrix of blood, i.e., plasma, is fluid in nature. Therefore, blood is called fluid connective tissue.

Question 18.
Classify different types of animal tissue.
Answer:
Classification of animal tissue is given below-

Question 19.
What are nodes of Ranvier?
Answer:
The continuity of myelin sheath on myelinated axon is interrupted by several constrictions. These are called nodes of Ranvier.

Long Questions and Answers : (5 marks for each question)

Question 1.
Describe the structure of epithelial tissue. Mention its main functions.
Answer:
Structure of epithelial tissue

The structure of epithelial tissue is as follows-

• The cells are present on a basement membrane made up of collagenous materials.
• Cells are densely packed and are joined together by mucoproteins (special type of glycoprotein).
• Cells of this tissue are either arranged in a single layer or in multi-layers.
• Cells do not get direct blood supply. They receive oxygen and nutrients from underlying tissues.

Functions of epithelial tissue
The functions of epithelial tissue are as follows —

• Epithelial tissue provides protection to animal body and its various organs.
• Epithelial tissue like squamous epithelium, takes part in gaseous exchange.
• Columnar epithelial cells help in absorption and secretion.
• Certain cuboidal and glandular epithelial cells secrete enzymes and hormones.

Question 2.
Mention the distribution of connective tissue. Briefly mention the structure of connective tissues.
Answer:
Distribution of connective tissue
The distribution of connective tissue is as follows-

• Areolar tissue is present below skin, between muscles, outer coatings of nerves and walls of blood vessels.
• Fibrous tissues are present in tendons, ligaments, walls of artery, trachea and larynx.
• Adipose tissue is found below skin, mammary glands, surrounding vital organs like heart, kidney etc.
• Bones and cartilages are found in the skeletal parts.
• Blood and lymph are present in the circulatory system.

Structure of connective tissue

The structure of connective tissue is as follows-

• Connective tissue originates from the mesoderm layer of the embryo.
• It possesses fewer cells, which remain loosely placed in the intercellular matrix.
• Cells of connective tissue are of various types with different size, shape, intra and intercellular components and functions.
• Some fibrous materials like collagen, elastin etc. may be present in the matrix.
• The matrix may be soft, jelly-like (areolar and adipose tissue), liquid (blood, lymph), rigid (bone), elastic (cartilage).

Question 3.
Briefly describe the structure of muscular tissue. Distinguish between muscular tissue and nervous tissue.
Answer:
Structure of muscular tissue
The structure of muscular tissue is mentioned below.

• Muscle cells are commonly called muscle fibres. These are thin, elongated, cylindrical or spindle shaped.
• Bundles of muscle fibres, surrounded by connective tissue, constitute a muscle.
• Muscle fibres may be uninucleated, multinucleated, unbranched or branched.
• The cytoplasm of muscle cell is called sarcoplasm, which remains surrounded by sarcolemma. Within sarcoplasm, several longitudinal contractile proteins are present, which help in the contraction and relaxation of muscles.

Differences between muscular tissue and nervous tissue:

Features	Muscular tissue	Nervous tissue
1. Origin	Mesoderm	Ectoderm
2. Distribution	With skeleton, visceral organs and heart	Brain, spinal cord and nerves all over body
3. Cell membrane	Sarcolemma	Axolemma
4. Number of nucleus	One or more	One
5. Processes	Absent	Present viz. axon and dendron
6. Function	Helps in movement and locomotion of organs and limbs	Transmission of nerve impulse

Question 4.
Describe the structure of a neuron.
Answer:
Structure of a neuron

Nerve cell or neuron has a typical structure as mentioned below.

• Neuron has two parts, the cell body or neurocyton and some processes.
• Neurocyton or cell body is covered by a typical cell membrane surrounding the protoplasm.
• Protoplasm has a distinct nucleus and cytoplasm with various cell organelles.
• Apart from mitochondria, Golgi body, ER etc., cytoplasm of a neuron has some nucleoprotein granules, known as nissl granules.
• Processes of a neuron are axon and dendron.
• Axon is the longer part with fewer branching. Few axons have an extra thick insulating cover on it, called myelin sheath.
• Myelin sheath is interrupted by several constrictions. These are called nodes of Ranvier.
• A special type of cell called Schwann cell, is also found along the length of the axon.
• The axon ends with few branches, commonly called as end brush.
• The dendron is shorter and well-branched. These branches are known as dendrites.

Question 5.
Mention the functions of different types of connective tissues. Distinguish between epithelial tissue and connective tissue.
Answer:
Functions of connective tissue
The functions of connective tissue are are follows-

• Areolar tissue acts as packing material between the organs.
• Adipose tissue stores fat for future use, keeps the body warm and acts as a cushion to protect the body against mechanical injury.
• Bones and cartilages form the skeleton, give mechanical support to the body of the vertebrates.
• Fibrous tissue provides elasticity and mechanical support.
• Blood and lymph act as transporting fluid, carrying nutrients, hormones, respiratory gases etc. and distributing them in all parts of the body.

Differences between epithelial and connective tissue

Features		Epithelial	Connective tissue
1. Origin		Ectoderm, mesoderm or endoderm	Mesoderm
2. Cellular arrangement		Densely packed and arranged in a layer	Scattered in a matrix
3 Quantity of intercellular matrix		Very little or completely absent!	Much more than the cellular components
4. Holding material		Basement membrane	Matrix
5. Function		Preparing a protective lining on external and internal organs	Connecting different parts, providing mechanical support and circulation

Question 6.
Compare the features of voluntary, involuntary and cardiac muscle.
Answer:
Comparison among voluntary, involuntary and cardiac muscle:

Features	Voluntary muscle	Involuntary muscle	Cardiac muscle
1. Striations	Present	Absent	Present
2. Number of nucleus	More than one	One	One
3. Arrangement of myofibrils	Longitudinal	Longitudinal	Longitudinal and transverse
4. Occurrence	With skeletal parts	Visceral organs	1 Heart
5. Branching	Unbranched	Unbranched	Branched
6. Nature of contraction	Voluntary	Involuntary	Involuntary
7. Working ability	Gets fatigued quickly	Gets fatigued slowly	Does not get fatigued

Question 7.
Distinguish between (i) Axon and dendron, (ii) Sarcolemma and neurlerama.
Differences between axon and dendron
Answer:

Features	Axon	Dendron
1. Comparative size	longer	Shorter
2. Branching	Less branched	Well branched
3. Myelin sheath	Present	Absent
4. Nodes of Ranvier	Present	Absent
5. Processes	Present	Absent
6. Function	Sending nerve impulse	Receiving nerve impulse

Differences between sarcolemma and neurolemms

Features	Sarcolemma	Neurolemms
1. Associated structures	Muscle fibres	Axon of neuron
2. Structural features	Plasma membrane of muscle cells	Outermost covering of axons
3. Function	Transmits nerve impulse to nerve cells from muscle cells	Serves a protective function for nerve cells

 

 

 

Detailed explanations in West Bengal Board Class 9 Life Science Book Solutions Chapter 4.2 Microbes in Human Welfare offer valuable context and analysis.

WBBSE Class 9 Science Chapter 4.2 Question Answer – Microbes in Human Welfare

Very Short Questions and Answers : (1 mark for each question)

Question 1.
Who is known as the father of microbiology?
Answer:
Louis Pasteur is known as the father of microbiology.

Question 2.
Give an example of a species of bacteria that is used for biological control of insect pest?
Answer:
Bacillus thuringiensis is used for biological control of insect pest.

Question 3.
Name a symbiotic bacterium, which can trap atmospheric nitrogen for its plant partner.
Answer:
Rhizobium leguminosarum can trap atmospheric nitrogen for its plant partner.

Question 4.
Which soil-living bacterium is applied in crop fields to increase nitrogen content of the soil?
Answer:
Azotobacter is a soil-living bacterium, which is applied in crop fields to increase nitrogen content of the soil.

Question 5.
Name a common viral bio-control agent against insect pest.
Answer:
Nuclear Polyhedrosis Virus is a common viral bio-control agent against insect pest.

Question 6.
Crystalline protein from which bacterium is popularly known as ‘cry protein’?
Answer:
Crystalline protein is produced from Bacillus thuringiensis bacteria, which is popularly known as ‘cry protein’.

Question 7.
Which bacterium is used to kill the larvae of Anopheles mosquito?
Answer:
Members of the Bacillus sphaericus bacteria are used to kill the larvae of Anopheles mosquito.

Question 8.
Name a bacterial species dwelling in the root nodules of leguminous plants.
Answer:
Rhizobium leguminosarum is a bacterial species dwelling in the root nodules of leguminous plants.

Question 9.
Name an endomycorrhiza, used as biofertiliser.
Answer:
VAM is an endomycorrhiza used as biofertiliser.

Question 10.
What is vermiculture?
Answer:
Vermiculture is the process in which earthworms are reared in a portion of soil to prepare organic manure to enhance the productivity of soil.

Question 11.
Name two fungal associates of mycorrhiza.
Answer:
Amanita and Boletus are two common fungal associates of mycorrhiza.

Question 12.
How does mycorrhiza help in reducing soil pollution?
Answer:
Mycorrhiza helps in reducing soil pollution removing harmful heavy metals like lead, mercury etc. from soil.

Question 13.
What is the full form of VAM?
Answer:
Full form of VAM is Vesicular Arbuscular Mycorrhiza.

Question 14.
Which types of mycorrhiza are found in nature?
Answer:
Three different types of mycorrhiza are found in nature, which are ectomycorrhiza, endomycorrhiza and ectendomycorrhiza.

Question 15.
Give examples of two fungi, which form ectomycorrhiza.
Answer:
Boletus and Amanita form ectomycorrhiza.

Question 16.
Give examples of two fungi, which form VAM or endomycorrhiza.
Answer:
Glomus and Acaulospora form VAM or endomycorrhiza.

Question 17.
Give exampies of two fungi, which forms ectendomycorrhiza.
Answer:
Clavaria and Endagon form ectendomycorrhiza.

Question 18.
Name two plants in which ectomycorrhiza grows on the roots.
Answer:
Ectomycorrhiza grows on the roots of oak and pine.

Question 19.
What is the full form of NPV?
Answer:
Full form of NPV is Nuclear Polyhedrosis Virus.

Question 20.
What is the full form of CPV?
Answer:
Full form of CPV is Cytoplasmic Polyhedrosis Virus.

Question 21.
Mention of the importance of NPV and CPV as bio-control agent.
Answer:
NPV and CPV are used to destroy several caterpillar pests of vegetable plants, hence, are bio-control agents.

Question 22.
Which type of phage virus is used to kill Salmonella bacteria in water bodies?
Answer:
Caudovirales is a group of phage virus used to control Salmonella build-up in water bodies.

Question 23.
Name a protozoan microbe, used to control insect pest.
Answer:
Nosema locustae is a protozoan microbe, used to control insect pests.

Short Questions and Answers : (2 marks for each question)

Question 1.
What are microhes?
Answer:
Microscopic organisms (less than 0.1 mm in diameter) present in air, water and soil are commonly known as microbes.

Question 2.
Which organisms are called bacteria?
Answer:
Prokaryotic microbes, having cellular diameter less than 3 μ m with cell wall typically made up of peptidoglycan and cytoplasm carrying a circular DNA and scattered 70 S ribosomes are called bacteria. Example-Bacillus, Salmonella etc.

Question 3.
Which organisms are called protozoa?
Answer:
Eukaryotic, unicellular microorganisms, carrying well-defined nucleus with chromosomes and membrane-bound cell organelles, are known as protozoa. Example-Amoeba, Plasmodium etc.

Question 4.
What is meant by bio-control agents?
Answer:
Different virus, bacteria, protozoa and insects can reduce the population growth of various insect pests of crops significantly, by causing disease, parasitism and predation. These biological agents are commonly called biocontrol agents.

Question 5.
What is meant by biological control?
Answer:
The technique by which abundance of pests and harmful organisms is controlled by application of their specific natural enemies is known as biological control.

Question 6.
Name two bacterial and two cyanobacterial species, commonly used as bio-fertilisers.
Answer:
The two bacterial species commonly used as bio-fertilisers are Rhizobium and Azotobacter. The two cyanobacterial species commonly used as bio-fertilisers are Anabaena and Nostoc.

Question 7.
What is meant by GM0?
Answer:
Full form of GMO is Genetically Modified Organism. By application of modern biotechnology, in recent days, plants and animals are produced with tailor made features. For this purpose unwanted genes of the organisms are replaced by desired genes, from outer source. Such organisms show desired features, and are popularly called genetically modified organism.

Question 8.
What are viruses?
Answer:
Viruses are ultra-microscopic, nucleoproteinated, acellular intermediate entity between living and non-living. Examples-HIV, Rotavirus etc.

Question 9.
What is biomagnification?
Answer:
The chemical fertilisers, insecticides, pesticides, which are used in conventional farming, enter into the food chain through producers. As these toxic chemicals pass along food chain from lower to higher trophic levels, the concentration increases step-by-step. This biological event is known as biomagnification. Biomagnification results into a number of diseases amongst the members of the higher trophic levels.

Question 10.
What is bioaccumulation?
Answer:
Bioaccumulation refers to accumulation of toxic substance in a organism. It occurs when an organism absorbs a toxic substance at a rate faster than that at which substance is lost by catabolism or excretion.

Question 11.
How do GMO help in bio-control of insect pests?
Answer:
Bacillus thuringiensis can produce a toxin, called Bt-toxin, which is fatal for insect pests. Biotechnologists have singled out the toxinproducing gene from the bacterium and placed it in the plant cells. Such GMO or Genetically Modified Crop plants synthesise the Bt-toxin, which potentially kill insect pests feeding on it.

Question 12.
Mention the role any of two viruses as biocontrol agents.
Answer:
1. Nuclear Polyhedrosis Virus can potentially kill the larvae of moths and beetles.
2. Granulosis virus destroys larvae of Spodoptera litura, an insect pest.

Question 13.
Mention the role of Caudovirales in controlling water pollution.
Answer:
Caudovirales is a group of phage viruses which kill Salmonella (bacteria) from water bodies. This phage virus can be used to eliminate Salmonella from drinking water to protect us from severe diarrhoea.

Question 14.
Mention the roles of any two protozoa as biocontrol agents.
Answer:
1. Nosema locustae is a protozoan microbe, which is used to control some insect pests.
2. Mattesia grandis, another protozoa, effectively controls cotton ball weevils.

Question 15.
Mention the role of a symbiotic bacteria as bio-fertiliser.
Answer:
Rhizobium leguminosarum is a symbiotic bacteria present in the root nodules of leguminous plants. These bacteria trap atmospheric nitrogen and convert it into nitrates. Ultimately this nitrate is transferred to their plant partners as an essential nutrient.

Question 16.
What is Azolla? Mention its importance.
Answer:
Azolla: Azolla is an aquatic floating fern which is commonly known as ‘mosquito fern’.

importance of Azolla: Azolla leaves give shelter to a nitrogen-fixing cyanobacteria named Anabaena azollae. Azolla is gown in water of paddy fields, Anabaena absorbs nitrogen from air. When water gets absorbed, Azolla decays and nitrogen gets mixed in soil to increase its fertility.

Question 17.
Why Azolla is an effective bio-fertiliser for paddy fields but not effective in wheat and vegetable fields?
Answer:
Azolla grows in water. Paddy plants also grow in wet soil. So, Azolla is grown in water of paddy fields. On the other hand, wheat and vegetables grow in drier soil. Therefore, application Azolla as bio-fertiliser is not effective for wheat and vegetable cultivation.

Question 18.
How do bacteria increase soil fertility?
Answer:
Bacteria can increase soil fertility in two different ways. One type increases nitrogen level in soil by trapping atmospheric nitrogen. Another type makes soil-borne phosphorus, soluble and absorbable to root system.

Question 19.
How Azotobacter can be applied in a crop field as bio-fertiliser?
Answer:
Agricultural laboratories prepare mixture of live Azotobacter cells and charcoal powder. This mixture can be applied in fields during soil preparation in the form of dust. This powder can also be mixed in water to prepare a bacterial solution. The seeds or roots of saplings may be given a dip in it before sowing and plantation.

Question 20.
How do phosphobacteria act as bio-fertiliser?
Answer:
Soil contains some phosphate salts, which are not absorbable by roots. Phosphobacteria make these salts soluble and absorbable to root system of plants. Thus, phosphobacteria act as a biofertiliser. Example-Bacillus megaterium is a phosphobacterium.

Question 21.
Mention the role of Bacillus thuringiensis as bio-control agent.
Answer:
Bacillus thuringiensis produces a toxin, called Bt-toxin, which can destroy larvae of many insect pests. In recent days Bt-toxin, popularly known as ‘thuricide’ is commerciallv prepared and applied in cotton and vegetable crop fields to control caterpillar and grub.

Question 22.
How do different bio-fertilisers work?
Answer:
Nitrogen-fixing bacteria and cyanobacteria propagate in soil and absorb atmospheric nitrogen, which ultimately mix in soil to make it fertile. Phosphobacteria convert phosphate salts into soluble and absorbable forms. Mycorrhiza removes harmful heavy metals (Pb, Cu, Hg, Cd etc.) from soil to reduce soil pollution and promotes plant growth. Certain microorganisms remove weeds.

Question 23.
What is the full form of IPM? Mention its objective.
Answer:
Full form of IPM: Integrated Pest Management.
Objective of IPM: The concept of Integrated Pest Management is developed in view of sustainable development of agriculture. Its main objective is to reduce the use of chemical fertilisers, insecticides, herbicides, fungicides by using bio-control agents or protect the future generation from harmful effects of these harsh chemicals and to keep the world as much pollution free as possible.

Question 24.
Mention the advantages of bio-control or biological controi.
Answer:
The advantages of biological control procedure are as follows-

1. Bio-control is more eco-friendly, because it does not pollute environment.
2. In bio-control, only the target pests are killed, the crop plant and other organisms remain unharmed.
3. This method is less expensive, therefore, reduces the production cost of crops.

Question 25.
Define mycorrhiza.
Answer:
Mycorrhiza is a symbiotic relationship between fungi and root systems of vascular plants. Mycorrhiza is formed in plants like pine, orchids etc. The fungi involved in the formation of the mycorrhiza are Glomus, Boletus etc.

Question 26.
Mention the disadvantages of bio-control measures.
Answer:
The disadvantages of bio-control procedures are-
1. Many bio-controlling organisms cannot adapt themselves with the new environment and often die.
2. The effectiveness of a bio-control agent on a pest cannot be assumed before application.

Question 27.
Describe the importance of VAM as biofertiliser.
Answer:
VAM or Vesicular Arbuscular Mycorrhiza is the most popular bio-fertiliser that enhances phosphorus, sulphur and copper absorption by root systems of plants with which it is associated.

Long Questions and Answers : (5 marks for each question)

Question 1.
Give a brief account of different microbial bio-control agents.
Answer:
Different microbial bio-control agents
Different bacteria, virus, fungi and protozoa can be used as bio-control agents.
1. Bacteria as bio-control agent: Bacillus thuringiensis produces a poison, called Bt-toxin, which is used to control growth of larvae of moths, beetles and flies. Scientists have introduced some genetic materials of these bacteria in corn, vegetables and cotton plants. As a result, Bt-toxin is synthesized in it, so that insect parasites cannot attack these plants. Pseudomonas fluonescena has been commercially used as fungicide. Bacillus popillae is used to control Japanese beetle, a pest of maple and rose plants.

2. Virus as bio-control agent:
Caudovirales is a group of phage virus, which kill Salmonella (bacteria) from water bodies. This phage virus can be used to eliminate Salmonella from drinking water to protect us from severe diarrhoea.

Nuclear Polyhedrosis Virus (NPV) or Cytoplasmic Polyhedrosis Virus (CPV) can kill larvae of moths and butterflies. These viruses are used to destroy some harmful insects like pine sawflies, gypsy moths, tussock moths etc.

3. Protozoa as bio-control agent:

• Nosema locustae is a protozoan microbe, which is used to control some insect pests.
• Mattesia grandis, another protozoa, effectively controls cotton ball weevils.

4. Fungus as bio-control agent: Beauveria bassiana is a fungus, which can control mosquito population effectively. It can be used in those areas, where mosquitoes have developed resistance against chemical insecticides. It can also control termites, whiteflies and many other insects.

Question 2.
What is meant by bio-fertiliser? Mention the roles of bacteria as bio-fertiliser. 1 + 4
Bio-fertiliser
Certain microorganisms, have the ability to promote plant growth by increasing the supply or availability of primary nutrients to plants. These are applied in crop fields to increase soil fertility. These are known as bio-fertiliser.

Roles of different bacteria as bio-fertilisers

1. Rhizobium leguminosarum is a symbiotic bacteria present in the root nodules of leguminous plants. These bacteria trap atmospheric nitrogen and convert it into nitrates. Ultimately this nitrate is transferred to the plant body as an essential nutrient.
2. Frankia is another symbiotic bacteria, which dwell in the root nodules of plants like Casuarina, Rubus, Alnus etc.
3. Some soil-living, aerobic bacteria can absorb atmospheric nitrogen into the cells. After death, this nitrogen is released in soil as nitrates and increases its fertility. Azotobacter sp., Azomonas sp., Derxia sp., Azospirillum sp. etc., are some examples.
4. Among the anaerobic nitrogen-fixing bacteria Clostridium sp., Chromatium sp., Chlorobium sp. are mentionable.
5. Some bacteria like Thiobaccilus, Micrococcus, Acrobacter are capable of solubilizing inorganic phosphorus from insoluble compounds in the soil. Use of these bacteria as bio-fertilisers enhance phosphate-nutrition of plants.

Question 3.
What do you mean by nitrogen fixation? Mention the roles of cyanobacteria as bio-fertiliser. 2 + 3
Answer:
Nitrogen fixation
Nitrogen fixation is a process in which nitrogen (N₂) in the atmosphere is converted into ammonia (NH₃). Nitrogen fixation process occurs naturally in the soil by nitrogen-fixing bacteria.

Roles of cyanobacteria as bio-fertilisers

Some cyanobacteria can trap atmospheric nitrogen. These include Anabaena sp., Nostoc sp., Aulosira sp., Stigonema sp., Plectonema sp., etc. These are now cultured in water of paddy fields. When these organisms die and decompose, nitrates get absorbed in soil and increase its fertility. Recently Azolla is being cultivated in the irrigated paddy fields. Azolla is an aquatic fern. Nitrogen-fixing cyanobacteria Anabaena azollae live in the leaves of this fern.

These cyanobacteria fix nitrogen from atmosphere and supply it to Azolla. Azolla die and get decomposed in the soil. By this process soil get nitrogen from the decomposed body of this fern. In Southeast Asian countries, cultivation of Azolla in paddy fields is a regular practice now. It has reduced the need for chemical fertilisers and has cut down the cost of paddy cultivation. Beside this, cyanobacteria secrete ascorbic acid, Vit. B and auxin in the soil.

Question 4.
Mention the roles of mycorrhiza as a bio-fertiliser. Why are bio-fertilisers and bio-control agents getting more acceptance all over the world? 2 + 3
Answer:
Roles of mycorrhiza as bio-fertiliser :
Mycorrhiza is a symbiotic association between roots of some vascular plants and some fungi. In this association, the fungi develop hyphae (fine filaments of fungal vegetative body) around the root-tip or inside the cortex of roots of the vascular plants. The fungal hyphae can absorb phosphorus and nitrogenous nutrients from soil very efficiently. It can also remove harmful heavy metals like lead, mercury etc., from the soil to reduce soil pollution. Mycorrhiza is formed in oaks, pines, orchids and some crop plants. The fungi involved in the formation of mycorrhiza are Boletus sp., Amanita sp., Glomus etc.

Reasons behind acceptance of bio-fertilisers and bio-control agents :

Chemical fertilisers are expensive. Production of these fertilisers need large infrastructure and power. Chemical fertilisers reduce natural soil fertility and change soil pH. Same is applicable in case of pesticides, these are very expensive and all of these materials increase environmental pollution. However, in comparison with chemical fertiliser production cost of bio-fertilisers is negligible.

Pest control by biological agents do not need any infrastructure at all. Bio-fertiliser does not need heavy infrastructure and power. Moreover bio-control is an eco-friendly procedure and bio-fertilisers do not cause soil pollution. Bio-fertiliser and pest control by biological agents not only retain the natural resources of earth, but also prevent it from getting amalgamated with chemical precipitations. So bio-fertilisers and bio-control agents are getting more acceptance all over the world.

Detailed explanations in West Bengal Board Class 9 Life Science Book Solutions Chapter 4.1 Immunity and Human Diseases offer valuable context and analysis.

WBBSE Class 9 Science Chapter 4.1 Question Answer – Immunity and Human Diseases

Very Short Questions and Answers : (1 mark for each question)

Question 1.
Which type of immunity develops by birth?
Answer:
Innate immunity develops by birth.

Question 2.
Which characteristic ability of antigen activates the immune system of the body?
Answer:
Immunogenicity of antigen activates the immune system of the body.

Question 3.
Which characteristic ability of antigen makes it compatible to the antibody?
Answer:
Antigenicity of an antigen makes it compatible to the antibody.

Question 4.
What is the name of the reaction shown by the body against any pathogen?
Answer:
The reaction shown by the body against any pathogen is commonly called immuneresponse.

Question 5.
What are allergens?
Answer:
The substances which trigger allergies are called allergens.

Question 6.
What is the name of the chemical, which is produced inside the body to resist a toxin?
Answer:
Antitoxin is produced inside the body to resist a toxin.

Question 7.
Which is the most abundant antibody present in human blood?
Answer:
Immunoglobulin G is the most abundant antibody present in human blood.

Question 8.
Which type of antiborly is present in ditierent body fluids and secretory materials in human body?
Answer:
Immunoglobulin A is present in different body fluids and secretory materials in the human body.

Question 9.
Which is the largest antibody present in our body?
Answer:
Immunoglobulin M is the largest antibody present in our body.

Question 10.
In which antibody five molecules stay as a ciuster?
Answer:
In Immunoglobulin M, five molecules stay as a cluster.

Question 11.
Where do B-lymphocytes mature?
Answer:
B-lymphocyte or B-cells mature in red bone marrow.

Question 12.
Which type of immunity is provided by neutrophils?
Answer:
Neutrophils provide innate immunity to the body.

Question 13.
How does an immunoglobulin G molecule appear?
Answer:
Immunoglobulin G molecules appear like English letter ‘Y’.

Question 14.
How many globulin chains combine to prepare an immunoglobulin G molecule?
Answer:
Two heavy and two light globulin chains combine to prepare an immunoglobulin G molecule.

Question 15.
How do the globulin chains remain tied together in an immunoglobulin G molecule?
Answer:
In an immunoglobulin G molecule the heavy and light chains remain tied together by di-sulphide bonds.

Question 16.
Which type of antibody can penetrate the placental barrier to reach the foetal blood from mother’s body?
Answer:
1gG can penetrate the placental barrier to reach the foetal blood from mother’s body.

Question 17.
Which antibody is present in tears?
Answer:
IgA is present in tears.

Question 18.
Which antibody is synthesised first in human foetus?
Answer:
The antibody synthesised first in human foetus is IgM.

Question 19.
Which antibody protects our body against allergens?
Answer:
IgE protects our body against allergens.

Question 20.
Which is the first line of defence in our immune system?
Answer:
Skin and mucus membrane provide the first line of defence in our body’s immune system.

Question 21.
Which is the second line of defence in our immune system?
Answer:
Phagocytic white blood cells like neutrophils and monocytes provide the second line of defence in our body’s immune system.

Question 22.
Which is the third line of defence of human immune system?
Answer:
Acquired immunity provided by different types of T and B-lymphocytes provides the third line of defence to human immune system.

Question 23.
What is meant by vaccination?
Answer:
Inoculation of the body with vaccines to develop active acquired immunity against specific disease-causing germs or toxins is called vaccination.

Question 24.
What is the full form of DPT vaccine?
Answer:
Full form of DPT is Diphtheria, Pertussis (whooping cough), Tetanus.

Question 25.
What is the full form of TT?
Answer:
Full form of TT is Tetanus Toxoid.

Question 26.
What is the full form of BCG?
Answer:
Full form of BCG is Bacillus CalmetteGuerin.

Question 27.
What is the full form of MMR?
Answer:
Full form of MMR is Mumps, Measles, Rubella.

Question 28.
What is the full form of ATS?
Answer:
Full form of ATS is Anti-Tetanus Serum.

Question 29.
What is the full form of OPV?
Answer:
Full form of OPV is Oral Polio Vaccine.

Question 30.
Give example of attenuated viral vaccines.
Answer:
Vaccines of mumps, measles, rubella, chicken pox belong to attenuated viral vaccines.

Question 31.
What is sub-unit vaccine?
Answer:
The vaccine which is prepared by certain molecular part of a pathogen, a viral protein for instance, is called sub-unit vaccine.

Question 32.
Give example of a sub-unit vaccine.
Answer:
Vaccine of Hepatitis B is a sub-unit vaccine.

Question 33.
To which kingdom of the living world does malaria pathogen belong?
Answer:
Malaria pathogen belongs to kingdom Protista.

Question 34.
What is full form of AIDS?
Answer:
Full form of AIDS is Acquired Immune Deficiency Syndrome.

Question 35.
Which day is observed as World Health Day?
Answer:
Every year 7th April is observed as the World Health Day.

Question 36.
Which day is observed as World AIDS Day?
Answer:
Every year 1st December is observed as the World AIDS Day.

Question 37.
Which disease is commonly known as Lock Jaw disease?
Answer:
Tetanus is commonly known as Lock Jaw disease.

Question 38.
What is the other name of ‘Break Bone fever’?
Answer:
The other name of ‘Break Bone fever’ is dengue.

Question 39.
Which type of hepatitis is transmitted through contaminated food and drink?
Answer:
Hepatitis A is transmitted through contaminated food and drink.

Question 40.
Which vaccine did Calmette and Guerin discover?
Answer:
Calmette and Guerin discovered the vaccine against tuberculosis.

Question 41.
Who discovered the vaccine of polio?
Answer:
Jonas Salk discovered the vaccine of polio.

Question 42.
Who discovered the Oral Polio Vaccine?
Answer:
Albert Sabin discovered the Oral Polio Vaccine.

Question 43.
Name a viral disease which is transmitted by mosquito.
Answer:
Dengue is a viral disease which is transmitted by mosquito.

Question 44.
Mention the full form of ‘WASH’ programme as proposed by UNICEF.
Answer:
The full form of WASH programme isWater and Sanitation Hygiene programme.

Question 45.
Name a virus, which causes severe diarrhoea.
Answer:
Rotavirus causes severe diarrhoea.

Question 46.
Name a bacterial disease, which causes fever, severe chest pain, cough and distressed breathing.
Answer:
Pneumonia causes fever, severe chest pain, cough and distressed breathing.

Question 47.
Name a disease caused by retrovirus.
Answer:
AIDS is caused by retrovirus.

Question 48.
Name two common household disinfectants.
Answer:
Phenyl and bleaching powder are two common household disinfectants.

Question 49.
How can you disinfect your hands without using water?
Answer:
Alcohol-based hand sanitisers can disinfect hands without water.

Short Questions and Answers : (2 marks for each question)

Question 1.
What is immunology?
Answer:
The branch of science, that deals with the study of antigens, antibodies and the overall immune system of the body, is known as immunology.

Question 2.
What is immunity?
Answer:
Immunity is defined as the defence mechanism of the body against a specific infection or toxin or any harmful foreign material, entering the body by the action of specific antibodies or specialised cells or agents.

Question 3.
What is an antigen?
Answer:
Antigens are foreign materials that stimulate the immune system of the body by inducing the synthesis of specific antibodies and sensitising immunologically significant white blood cells.

Question 4.
Mention the characteristic features of antigens.
Answer:
Characteristic features of antigens are as follows-

1. Antigens are commonly proteins, or polysaccharides in nature
2. Antigens are generally of high molecular weight. Minimum molecular weight of an antigen is 10000 Dalton.
3. An antigen induces the synthesis of a specific antibody.

Question 5.
What are the common sources of antigens?
Answer:
The common sources of antigens are as follows-

1. Surface proteins of bacteria and viral capsid are the common sources of antigens.
2. Different toxins, snake venom, sting poisons of bees, wasps, scorpions act as antigens.
3. Secretory or excretory materials of bacteria or parasites contain antigens.
4. Some chemicals, drugs, pollen grains even food materials contain allergic antigens (allergens).

Question 6.
What are exogenous antigens?
Answer:
The antigens, which enter into the body from outside, are called exogenous antigens. Exogenous antigens include different diseasecausing germs, certain allergic food materials, chemicals, pollen grains.

Question 7.
What is endogenous antigen?
Answer:
The antigenic materials, which are synthesised inside the body and are capable of inducing immune response are called endogenous antigens. Certain proteins present on the surface of RBC, cardiolipin of mammalian heart, prostate specific antigen of prostate gland are the examples of endogenous antigens.

Question 8.
What is an antibody?
Answer:
Antibodies are immunoglobulin molecules, which are produced or remain in blood to counteract and inactivate specific antigens and thereby protect the body against their harmful effects.

Question 9.
Mention the characteristic features of antibodies.
Answer:
Characteristic features of antibodies are as follows-

1. Antibodies are glycoproteins commonly called immunoglobulins.
2. Molecular weight of an antibody ranges from 150000 to 950000 Dalton.
3. Antibodies are antigen-specific.

Question 10.
How do antibodies work?
Answer:
Antibodies work through following methods-

1. Antibodies or immunoglobulins bind to specific antigens to agglutinate and precipitate them.
2. Some antibodies bind to antigens to let those to be phagocytized by macrophage cells.
3. Some antibodies immobilize and dissolve antigens.

Question 11.
How many types of antibodies are found in human body?
Answer:
Human body contains five different types of antibodies or immunoglobulins. These are IgA, Ig D, Ig E, Ig G and IgM.

Question 12.
What is primary immune response?
Answer:
The reactions in the body in response to an antigen for the first time is called primary immune response. This response takes a little more time (10-17 days) for recognition of the antigen.

Question 13.
What is secondary immune response?
Answer:
The reactions in response to an antigen, already known to the body’s immune system, is known as secondary immune response. This response is very fast (2-7 days) because memory cells, already produced in the body, recognise the antigen and respond instantaneously.

Question 14.
What is meant by cell-mediated immunity?
Answer:
The immune response, which involves activity of the cytotoxic T-lymphocytes and different phagocytic cells in destroying the pathogens or pathogen infected cells within the body, is called cell-mediated immunity.

Question 15.
What is meant by innate immunity?
Answer:
The innate immunity refers to non-specific defence mechanisms that come into play immediately or within hours of an antigen’s appearance in the body.

Question 16.
What is meant by acquired immunity?
Answer:
The immunity, which develops within the body of an organism by any infection, vaccination or by introduction of antibody artificially, is called acquired immunity.

Question 17.
Schematically represent different types of acquired immunity.
Answer:
Schematic representation of different types of acquired immunity is given below-

Question 18.
What is meant by active acquired immunity?
Answer:
The immunity, which is developed in the body of an organism by introduction of an antigen, naturally or artificially, is called active acquired immunity.

Question 19.
What is artificial active immunity?
Answer:
The active immunity, which develops in an organism after vaccination is called artificial active immunity. Examples-Vaccines like DPT, OPV, BCG etc. develop artificial active immunity.

Question 20.
What is passive acquired immunity?
Answer:
The immunity which is developed in the body of an organism by introduction of an antibody, naturally or artificially, is called passive acquired immunity.

Question 21.
What is natural active immunity?
Answer:
The active immunity, which is developed in an organism after natural infection by any pathogen (virus, bacteria etc.) is known as natural active immunity. Example-After infection of chicken pox, a person develops natural active immunity against this disease and is not attacked by the same disease in future.

Question 22.
What is natural passive immunity?
Answer:
The passive immunity, which is developed by the inflow of antibodies from mother to the foetus through placental circulation is known as natural passive immunity. Example-Immunoglobulin A, acquired by a baby through colostrum of breast milk of the mother, develops natural passive immunity.

Question 23.
What is artificial passive immunity?
Answer:
The passive immunity, which develops in an animal by introduction of antibodies from outside by injection, is known as artificial passive immunity. Example-Antitoxin serum, produced from horse’s blood, is injected to save the life of a person suffering from snake bite.

Question 24.
What is the importance of vaccination?
Answer:
Importance of vaccination are as follows-
1. By means of vaccination specific antibody develops within our body. Memory cells develop in the body, which remain stored in lymphatic system to counter any chance of infection by the same pathogen in future.
2. Certain vaccines develop immunity for lifetime and some others immunize the body for a certain period.

Question 25.
What is meant by attenuated vaccine?
Answer:
The vaccines, which are prepared by living but inactivated pathogens (bacteria or virus) are called attenuated vaccines. Examples-Vaccines of tuberculosis, mumps, influenza, and Oral polio vaccine (Sabin vaccine) belong to attenuated vaccine.

Question 26.
What is meant by killed vaccine?
Answer:
The vaccines, which are prepared with dead or inactivated bacteria or virus, are known as killed vaccines. Examples-Vaccines of typhoid, cholera, whooping cough (pertussis), rabies, hepatitis B and Salk vaccine belong to killed vaccine category.

Question 27.
What is a toxoid?
Answer:
Toxins collected from pathogenic microorganisms, are chemically detoxified keeping their antigenic property intact. These preparations are used as vaccines, which are called toxoids. Examples-Tetanus and diphtheria vaccines are of this type.

Question 28.
What is meant by combination vaccines?
Answer:
Certain vaccines are prepared with different antigens to immunize individuals against more than one disease by a single inoculation. These vaccines are called combination vaccines. Examples-DPT (Diphtheria, Pertussis, Tetanus) vaccine, MMR (Mumps, Measles, Rubella) vaccine are of this type.

Question 29.
What is booster dose of vaccine?
Answer:
To maintain a steady stock of memory cells in the immune system certain vaccines are applied at regular intervals. These slots of vaccines are known as booster dose. Example-Booster dose of tetanus toxoid must be given after every ten years.

Question 30.
Mention the causative agents of diarrhoea. How is the disease transmitted?
Answer:
Causative agents of diarrhoea: Diarrhoea is caused by ETEC- Enterotoxigenic E. coli, Salmonella sp. (bacteria), Rotavirus (virus).
Mode of transmission of diarrhoea: This disease is transmitted through contaminated food and water.

Question 31.
What in meant by primary lymphoid organ?
Answer:
The organs, within which T and B lymphocytes attain maturity, are called primary lymphoid organs. Example-Thymus gland, the site of maturity of T-cells and red bone marrow, the tissue where B-cells mature, are the two primary lymphoid organs.

Question 32.
What is secondary lymphoid organ?
Answer:
Matured T and B-lymphocytes are transferred to some other organs for further proliferation. These organs are known as secondary lymphoid organs. Example-All lymph glands, especially tonsils and spleen are the examples of secondary lymphoid organs.

Question 33.
Write the common symptoms of diarrhoea.
Answer:
Common symptoms of diarrhoea are –

1. frequent watery stool,
2. abdominal pain and cramps,
3. disability to hold bowel movement,
4. nausea and fatigue,
5. thirst and dehydration.

Question 34.
Mention the names of different malaria causing pathogens. How is malaria transmitted?
Answer:
Causative agents of malaria: Malaria is caused by different species of Plasmodium, a parasitic protozoan. They are Plasmodium vivax, P. falciparum, P. malariae and P. ovale.
Transmission of malarial parasite: Female Anopheles mosquito carries Plasmodium from a diseased individual to a healthy person.

Question 35.
Write down the different symptoms of malaria.
Answer:
The symptoms of malaria are-

1. chilled feeling with severe shivering
2. severe headache, [3] very high fever (104 °F or more)
3. remission of fever with profuse sweating
4. fatigue
5. nausea.

Question 38.
Name the causative agent of diphtheria. How is the disease transmitted?
Answer:
Causative agent of diphtheria: Causative agent of diphtheria is a bacterium named Corynebacterium diphtheriae.
Mode of transmission of diphtheria: Diphtheria is transmitted mainly through respiratory droplets. This disease also spread by touching the body of an infected person and from contaminated materials like telephone, utensils, towels, handkerchiefs etc.

Question 37.
Mention the symptoms of diphtheria.
Answer:
The symptoms of diphtheria are-

1. thick, gray coating over pharyngeal wall and tonsils
2. sore throat and hoarseness
3. swelling of lymph glands near the neck
4. distressed breathing and swallowing
5. nasal discharge
6. high fever.

Question 38.
Name the causative agent of pneumonia. How is the disease transmitted?
Answer:
Causative agent of pneumonia: Causative agent of pneumonia is a bacterium named Streptococcus pneumoniae.
Mode of transmission of pneumonia: The pathogens of pneumonia are transmitted through respiratory droplets from the nose and mouth of a sick person.

Question 39.
Mention the symptoms of pneumonia.
Answer:
The symptoms of pneumonia are

1. severe cough
2. distressed breathing
3. chest pain, especially with cough
4. fever
5. breathlessness
6. fatigue.

Question 40.
Name the causative agent of tetanus. How is the disease transmitted?
Answer:
Causative agent of tetanus: Causative agent of tetanus is Clostridium tetani.
Mode of transmission of tetanus: Pathogen of tetanus is transmitted directly from soil through open wounds or injuries. Injuries from contaminated nails, knives, razors, surgical instruments etc. also transmit this disease.

Question 41.
Mention the symptoms of tetanus.
Answer:
The symptoms of tetanus are-

1. fever followed by jaw cramping,
2. spasm in stomach,
3. stiffness of muscles with severe pain,
4. trouble in swallowing,
5. high blood pressure and fast heart rate.

Question 42.
Name the causative agent of tuberculosis. Mention the symptoms of tuberculosis.
Answer:
Causative agent of tuberculosis: Causative agent of tuberculosis is a bacterium named Mycobacterium tuberculosis.
Symptoms of tuberculosis:

1. Night fever with sweating,
2. Dry cough with blood-tinted sputum,
3. Significant weight loss,
4. Fatigue.

Question 43.
How is tuberculosis transmitted?
Answer:
Tuberculosis is transmitted through respiratory droplets from nose and mouth of a diseased person. Exhaled air of the patient carries pathogens of this disease. Inhaling this air from a distance of a few metres, may infect another person with the same disease.

Question 44.
Name the causative agent of dengue. How is dengue transmitted?
Answer:
Causative agent of dengue: Causative agent of dengue is Flavivirus.
Mode of transmission of dengue: Female Aedes aegepti mosquito (which is a blood sucking ectoparasite) carries dengue virus from a diseased person to a healthy individual.

Question 45.
Mention the symptoms of dengue.
Answer:
The symptoms of dengue are-

1. high fever with severe headache
2. pain behind the eyes
3. severe body ache and joint pain
4. rash over skin
5. moderate bleeding from gums.

Question 46.
Name the causative agent of hepatitis A. How is hepatitis A transmitted?
Answer:
Causative agent of hepatitis A: Causative agent of hepatitis A is HAV or Hepatitis A Virus.
Mode of transmission of hepatitis A: This virus comes out through faeces of a person, infected with hepatitis A. The pathogen is then transmitted through contaminated food (raw vegetables) or drinks (water) in a healthy person.
Therefore, in other words it can be stated that this infection is transmitted through faecal-oral route.

Question 47.
Mention the symptoms of hepatitis A.
Answer:
The symptoms of hepatitis A are –

1. nausea and vomiting
2. liver pain
3. loss of appetite
4. darkish urine
5. yellowing of skin and eye.

Question 48.
Name the causative agent of hepatitis B. How is hepatitis B transmitted?
Answer:
Causative agent of hepatitis B: Causative agent of hepatitis B is HBV or Hepatitis B Virus.
Mode of transmission of hepatitis B: This virus is carried by blood or other body fluids. It is transmitted through transfusion of contaminated blood, and sharing same injection needle with a patient. This virus may pass through placenta, therefore, infect a foetus of a diseased mother. It may be transmitted by sexual contact also.

Question 49.
Mention the symptoms of hepatitis B.
Answer:
The symptoms of hepatitis B are-

1. nausea and vomiting,
2. abdominal pain,
3. loss of appetite,
4. darkish urine,
5. yellowing of skin and eye,
6. severe fatigue.

Question 50.
Name the causative agent of AIDS. How is AIDS transmitted?
Answer:
Causative agent of AIDS: The causative agent of AIDS is HIV or Human Immunodeficiency Virus.
Mode of transmission of AIDS: The virus of AIDS is transmitted by transfusion of contaminated blood, sharing same injection needle with a patient, through unsafe sexual contact, from mother to foetus through placental circulation.

Question 51.
Mention the symptoms of AIDS.
Answer:
The symptoms of AIDS are-

1. recurrent fever
2. common cold-like symptoms
3. frequent diarrhoea
4. quick loss of weight
5. swelling of glands in groin
6. fatigue
7. joint pain
8. persistent skin rashes.

Question 52.
What is meant by washing?
Answer:
The process of disinfecting hand and other body parts, garments, utensils, raw food matters, like fish, meat, vegetables and fruits with clean water, soap, detergents or germicidal lotions is known as washing.

Question 53.
Mention the role of different washing materials?
Answer:
The role different washing materials are as follows-

1. Water is used to wash all items.
2. Detergents are used to wash garments, beddings and utensils.
3. Floor cleaners are used to clean floors of room and toilet.
4. Soap, shampoo and shower gels are used in bathing.
5. Hand is washed with soap and disinfecting lotion.

Question 54.
Briefly describe the importance of brushing teeth.
Answer:
Unhygienic oral condition leads to different problems like tooth decay, gum disease, bad breath, pyorrhoea, loosening and falling of teeth. Proper brushing with toothpaste helps in reducing plaque and germ build up in the mouth and reduces the chances of oral problems. For this purpose brushing of teeth is to be done essentially before going to bed.

Question 55.
Why is bathing important for good health?
Answer:
Population of different bacteria, fungi and ectoparasites grow fast on unclean body surface. Sweat and sebum provide the germs a good medium for nutrition and growth. Unclean body surface leads to several skin infections. By regular bathing, these germs are washed off. Therefore, bathing is important to maintain a good health.

Question 56.
What should be the proper bathing technique?
Answer:
To clean the body surface shower with clean water is necessary. Then soap or bathing gel is to be applied and then rubbed with a scrubber to create rich foam. More attention is to be given at the hidden parts like armpits, groins, as these regions provide good places for germ build-up. Finally, the foam is to be cleared with adequate water to get a clean and hygienic skin.

Question 57.
Why are washing and sun drying of garments, beddings, bathing towels, handkerchiefs essential for maintaining hygiene?
Answer:
Pathogens of scabies, ringworm, eczema and a number of allergens spread through contaminated garments, beddings, bathing towels and handkerchiefs. Washing can reduce the population of pathogens from these materials. Therefore, washing and sun drying of these items is essential for maintaining a good hygiene.

Question 58.
Why is washing of hand essential before taking food?
Answer:
We commonly take food by hand. A contaminated hand may carry the pathogens of various diseases like diarrhoea, dysentery, hepatitis A, cholera, gastroenteritis. By washing hand before taking food, the occurrence of these diseases can be reduced to a great extent.

Question 59.
Why an open wound should be washed with germicidal lotion?
Answer:
Skin acts as a great barrier against the entry of germs into our body. However, open wounds become a good entry point for various germs. Therefore, any open wound is to be washed with germicidal lotions to kill the germs in the wound and at its periphery. After washing, the wound must be covered with sterilised bandage, gauge or cotton to resist the entry of germs through it.

Question 60.
What are ‘paratope’ and ‘epitope’?
Answer:
The part of antibody that adheres to antigen is known as ‘paratope’ and the part of the antigen, attached to the paratope is known as ‘epitope.’

Question 61.
What is interferon (IFN)?
Answer:
Interferon is a group of proteins that is formed and released by the host cells in response to pathogens specially virus. These are highly effective in combating hepatitis, influenza etc.

Question 62.
What is MALT?
Answer:
The full form of MALT is Mucosa Associated Lymphoid Tissue. These types of lymphoid tissues are located within the lining of respiratory tract, digestive tract and urino-genital tract and it constitutes 50 % of lymphoid tissues in human body.

Question 63.
What is the main objective of vaccination?
Answer:
Generating memory cells in the blood to recognise a specific antigen for quick triggering of immunological response in case of infection by the same pathogen in future is the main objective of vaccination.

Question 64.
Distinguish between innate and acquired immunity.
Answer:

Features	Innate immunity	Acquired immunity
1. Activation	Becomes active with birth	Becomes active in presence of antigen
2. Specificity	It is nonspecific immune response	It is specific immune response

Question 65.
Distinguish between active acquired immunity and passive acquired immunity.
Answer:

Features	Active acquired immunity	Passive acquired immunity
1. Source of antibody	Originates inside the body with introduction of any antigen	Enters into the body from mother’s body or from other animal source
2. Span of action	Develops slowly but remains active for a long time	Acts instantaneously

Long Questions and Answers : (5 marks for each question)

Question 1.
Briefly describe the structure of the most common antibody present in human plasma. Distinguish between antigen and antibody. 3 + 2
Answer:
Structure of antibody

Immunoglobulin G or IgG is the most common antibody present in human plasma. Its structure is mentioned below.
1. Immunoglobulin G molecule is a ‘Y’ – shaped structure.
2. Each molecule has a specific antigen-binding site, by which it attaches with a specific antigen to inactivate it.
3. The immunoglobulin molecule is composed of 4 polypeptide chains of which two are heavier and two others are lighter in weight. These chains remain attached with di-sulphide bonds.
4. The two forked arms are made up of one light and one heavy chain each. The stem arm of IgG molecule is composed of two heavy chains.

Differences between antigen and antibody

Features	Antigen	Antibody
1. Occurrence	Enters into body from outside (rarely synthesised inside body)	Occurs within the body in the presence of antigen
2. Effect	Causes harm to the body	Protector of the body
3. Chemical nature	Glycoprotein, lipoprotein or polysaccharide	Generally glycoprotein
4. Function	Activates the immune system of the body	Inactivate or destroy antigens

Question 2
Briefly describe the mechanism of immune response against viral attack in human body. Mechanism of immune response against a viral attack
Answer:
Immune response is a complex process involving various cells and biochemical components inside the body.

The steps of immune response against viral antigen are as follows –

1. As any virus reaches blood or attacks any body cells, large phagocytic macrophages engulf those infected cells. Soon viral antigens appear on the cell surface of macrophages.
2. High concentration of viral antigens on macrophage activates helper Tlymphocytes in blood.
3. Helper Tcells immediately initiate the production of cytotoxic killer T-cells, memory T-cells and B-lymphocytes.
4. B-lymphocytes proliferate very fast to produce plasma cells and memory B-cells.
5. Plasma cells produce specific antibodies to bind and inactivate virus before they get chance to infect a cell.
6. Killer Tcells destroy the infected body cells along with viruses.
7. T and memory B- cells stay in the body to recognize the same pathogen in case of further infection and to develop quicker response.

Question 3
What is humoral immunity? How does humoral immunity work?
Answer:
Humoral immunity
The immune response, which involves the action of different B-lymphocytes, like plasma cells, for producing antigen-specific antibodies and memory cells for neutralizing or eliminating toxins and pathogens in the blood and lymph is called humoral immunity.
Mechanism of humoral immunity –
Humoral immunity works for both primary and secondary immune response.
In primary response B-lymphocytes develop typical antibody-producing plasma cells. These cells produce antigen

specific antibodies. Antibodies work in following four ways.

1. Agglutination: By this process antibodies agglutinate pathogens into clusters, which are then collectively phagocytized by macrophages.
2. Precipitation: Some antigen molecules are clamped by antibodies and are precipitated.
3. Opsonisation: Antibodies form a covering on the antigens so that the phagocytic cells ingest packed antigens.
4. Neutralisation: Certain toxic antigens are detoxified and inactivated by the antibodies.

In secondary response memory B-cells play the major role. These cells are produced during primary immune response and remain stored in the secondary lymphoid tissues for keeping the immunological behaviour of the pathogen in memory of the body’s immune system. In case of another attack, these cells help in quick activation of body’s immune system.

Question 4.
Mention the roles of different T-cells in immune response? Mention the roles of different B-cells in immune response? 3 + 2
Answer:
Roles of different T-cells
Different T-cells or T-lymphocytes play different roles in immune response of the body. They are as follows-
1. Cytotoxic T-cells or T_C-cells kill the infected cell, to destroy antigen carrying pathogens within it.
2. Helper T-cells or T_H-cells enhance the activity of killer cells (a type of T_C – cells), antibody producing B-cells and phagocytic macrophages.
3. Suppressor T-cells or T_S-cells destroy T_C-cells, T_H-cells and B-cells to stop immune response after the elimination of the antigens.

Roles of different B-cells :
Different B-cells or B-lymphocytes play different roles in immune response of the body. They are as follows-
1. Plasma cells originated from B-cells produce specific antibodies to inactivate antigens.
2. Memory B-cells remain in lymph glands, keeping the nature of antigens in memory, take quick action in case of any further attack.

Question 5.
Mention the differences between B-cells and T cells.
Answer:
Differences between B-cells and T-cells

Features	B-cells	T-cells
1. Maturation	Lymphoid tissue or bone marrow	Thymus
2. Longivity	Short (few days to a week)	Long (months to years)
3. Surface immunoglobulins	Present	Absent
4. Type of immunity	Humoral immunity	Cell mediated immunity
5. Secretary product	Antibodies	Lymphokines
6. Defence mechanism	Defend against pathogens that enter the blood and lymph	Defend against pathogens that enter the cells
7. Inhibition	Have no inhibitory effect on immune system	Suppressor cells inhibit immune system

Question 6.
Give a brief historical account of the discovery of small pox vaccine.
Answer:
Discovery of small pox vaccine
The scientific concept of vaccination was developed in the later half the of 18th century when a number of scientists and physicians were working hard to develop a vaccine against small pox, the most deadly and contagious disease of that time. Scientists noticed that most individuals, who once suffered from cow pox safely bypassed small pox. But the search was on for long 25 years. Then Dr. Edward Jenner (1798) broke through the concept of vaccination. He collected a little pus from a cow pox vesicle on the hand of Sarah Nelmes, a milkmaid, and introduced it into the arm of James Phipps, an eight year old boy.

After two months, the boy was inoculated with small pox virus, but he did not develop the disease. The modern concept of vaccination is standing on this story. After this discovery, the practice of vaccination took the correct route. After a long battle for about two centuries, small pox has now been eradicated from the world.

Question 7.
What is a vaccine? Mention the basic working principles of vaccines to develop immunity in the body. 2 + 3
Answer:
Vaccine
Vaccine is an antigenic material that is prepared with killed or weakened pathogens, part of pathogens, bacterial toxins or microbial proteins, which do not cause illness but provide active acquired immunity against those pathogens when introduced into the body.

Working principle of vaccines
By vaccination, a killed germ, attenuated (weakened) germ, toxoids (toxins collected from germs) or subunits (fragments of proteins from germs) are introduced into the body of an individual. These may be injected or administered orally. As soon as the substance enters the body, antigens present in it, activate the immune system and initiate an immune response. T-cells and B-cells take a little time to inactivate such little quantity of antigens and this process is known as primary immune response.

However, in this case, main function is done by memory B-cells. These cells, produced during the immune response, are retained in lymph nodes such as spleen, thymus etc.. for a long time. In case of any future infection by the same germ, these memory cells recognize those antigens instantly and inactivate or destroy the attacker very fast. This process is recognized as secondary immune response. Thus, a successful vaccination immunizes a person effectively.

Question 8.
Give a brief account of different types of vaccines.
Answer:
Types of vaccines

With the development of science, new and advanced varieties of vaccines are being developed. Till date World Health Organisation (WHO) has licensed vaccines for 25 diseases. Different types of vaccines are:
1. Killed vaccine: These vaccines contain killed pathogens. Vaccines of cholera, plague, influenza are of this type.

2. Live attenuated vaccine: By some laboratory techniques virulence of the pathogens are reduced to prepare this type of vaccines. Vaccines of mumps, measles, and rubella are of this type.

3. Toxoid vaccine: This type of vaccine is prepared by inactivated toxins from pathogens. Vaccines of tetanus, diphtheria are of this type.

4. Conjugate vaccine: Generally polysaccharide of bacterial capsule is attached with a protein to prepare this vaccine. Body’s immune system can recognise this conjugated protein and keep it in memory for future immune response. Vaccine against Haemophilus influenzae type-B is of this type.

5. Sub-unit vaccine: This type of vaccine is prepared by small fragments of pathogenic protein. Vaccine against Hepatitis B is of this type.
Heterotypic vaccine: This is prepared by pathogens, causing disease to other animals but less or non-virulent to human. Vaccines of small pox and tuberculosis are of this kind.

Question 9.
Why and when should an individual wash hands? Write down the proper method of washing hand. 1 + 2 + 2
Answer:
Reason of washing hand
We take food with hand. We often touch our lips, face and nose with our hands. By contaminated hands, germs or toxins may enter our body through mouth, eyes and nose. Therefore, one must wash the hands to stay healthy.

Time of washing hand
Hands must be washed before –

1. taking food
2. cooking
3. serving food
4. feeding and attending a baby or a patient.

Proper washing of hand is a must after using toilet, cleaning raw vegetables, fish and meat, attending a patient, sweeping and cleaning rooms and toilets, polishing shoe and tying shoe-laces, checking air pressure of cycle tyre, coming home from outside, etc.

Proper method of washing hand :
Proper method of washing hand is mentioned below.

1. Wet the hands with clean water.
2. Take liquid hand-wash or soap in wet hands and rub it for one or two minutes to make rich foam.
3. Carefully rub in between all fingers.
4. Place the hands under running water and continue rubbing until the foam clears.
5. Close tap with clean cloth and wipe the hand with dry and clean towel.

Question 10.
Wilte a short note on ‘WASH’ programme of UNICEF.
Answer:
‘WASH’ programme of UNICEF
Percentage of healthy children in a population is the index of development of a nation. But it is unfortunate that even in the 21 st century, millions of children suffer from diarrhoea and several other water-borne diseases. This happens because of contaminated water, which occurs mostly due to lack of proper sanitation. 44 % of global population defecate in open areas. Faeces contain numerous germs, which easily contaminate water, especially during rainy season.

In view of that, UNICEF (United Nations International Children’s Emergency Fund) has developed a global strategy to lift the standard of health of school children by providing them adequate drinking water, infrastructure for proper sanitation and sense of hygiene. This programme is popularly known as ‘WASH’ (Water Sanitation Hygiene programme). United Nations has set a goal for sustainable development of the standard of living of world population in this millennium. To reach the target, UNICEF has developed a strategy to maximise child survival rate by providing an access to adequate drinking water, sanitation facilities to schools all over the world along with education and nutrition

Question 11.
Describe the WASH strategy taken by UNICEF to improve hygiene behaviour among school children. How can the WASH programme be made successful? 3 + 2
Answer:

WASH strategy to improve hygiene behaviour among school children Schools are the places where a child spends most of the time of his or her life all through the development period. So UNICEF has developed the plan to make every school a child-friendly place. In view of that UNICEF has extended both monetary and strategic support to all developing countries of the world to develop infrastructure for child-friendly schools. The strategy to enhance child survival and development, UNICEF has encouraged a three pillar approach. The first is enabling a child-friendly environment in the school. Next is to improve hygiene behaviour among the students and the third one is to build infrastructure for water supply and sanitation services.

Points to make WASH successful :
The points to make WASH successful are as follows-

1. Wash your hands with adequate water and soap before taking food and after using toilets.
2. Always use sanitary toilets.
3. Clean raw fruits and vegetables before consuming.
4. Keep a close vigilance on drinking water sources to reduce contamination to zero.
5. Clean water storage containers every day.
6. Keep your domestic and school toilets clean.
7. Clip your nails regularly and do not let any filth to deposit under it.

Question 12.
Mention different hygienic practices to secure good health of a person as well as of the society.
Answer:
Different types of hygienic practices
The conditions or practices helpful to maintain health and to prevent diseases, especially through cleanliness are known as hygiene. Hygiene can be practiced in three different levels, i.e., personal, household and social levels, which are mentioned below.
1. Personal level hygiene:

• Cleaning hands before taking food, after using toilet and handing any unclean material.
• Brushing teeth after taking meal and before going to bed.
• Taking bath once or twice a day.
• Trimming hair and clipping nails regularly.

2. Househoid level hygiene:

• Washing and sun-drying clothing and bedding at regular intervals.
• Cleaning utensils, kitchen equipment, raw vegetables, fish and meat.
• Cleaning toilet, basins and sinks.
• Cleaning and disinfecting water reservoirs.

3. Social level hygiene:

• Cleaning of sewage system at regular interval.
• Maintaining general cleanliness in hospitals, educational institutions, market places, railway stations, bus terminus,
• auditoriums, theaters and other community places.
• Regular cleaning and disinfecting public toilets.

Detailed explanations in West Bengal Board Class 9 Life Science Book Solutions Chapter 2.3A Tissue: Plant Tissue and its Distribution offer valuable context and analysis.

WBBSE Class 9 Science Chapter 2.3A Question Answer – Tissue: Plant Tissue and its Distribution

Very Short Questions and Answers : (1 mark for each question)

Question 1.
Which type of parenchyma is involved in it aiding photosynthesis within it?
Answer:
Chlorenchyma is involved in holding photosynthesis within it.

Question 2.
Which type of tissue in fruits form roughage a our food diet?
Answer:
Fruits containing sclerenchyma tissue, form roughage of our food diet.

Question 3.
Which tissue is also known as leptome?
Answer:
Phloem tissue is also known as leptome.

Question 4.
Which type of simple permanent tissue has evenly thick cell wall around dead cells?
Answer:
Sclerenchyma has evenly thick cell wall around dead cells.

Question 5.
Which type of scierenchyma cells make the fruits like guava, pear etc. harder?
Answer:
Sclereid cells make the fruits like guava, pear etc. harder.

Question 6.
How do the large air-filled intercellular spaces of parenchyma tissue in petioles of lotus plant help it?
Answer:
The large air-filled intercellular spaces of parenchyma tissue in petioles of lotus plant help it to maintain its buoyancy and to float on water.

Question 7.
Which is the non-living component of phloem?
Answer:
Phloem fibre is the non-living component of phloem tissue.

Question 8.
Which type of tissue is the cork cambium?
Answer:
Cork cambium is a secondary meristematic tissue.

Question 9.
From which type of tissue does permanent tissue develop?
Answer:
Permanent tissues develop from meristematic tissue.

Question 10.
Name the cells of parenchyma tissue in which plants store their excretory matter.
Answer:
Plants store their excretory matter in idioblast cells of parenchyma tissue.

Question 11.
Which type of meristem occurs along the longitudinal plane of the plant body?
Answer:
Lateral meristem occurs along the longitudinal plane of the plant body.

Question 12.
Which type of meristem is seen in the leatbase of pine?
Answer:
Intercalary meristem is seen in the leaf-base of pine.

Question 13.
Which simple permanent tissue is totally devoid of intercellular space?
Answer:
Sclerenchyma tissue is totally devoid of intercellular space.

Question 14.
Which cells do not directly take part in transportation of food in plants but help in this process?
Answer:
Companion cells do not directly take part in food transport but help sieve tubes to do so.

Question 15.
Which simple permanent tissue is responsible for adding mechanical strength to the plant body?
Answer:
Sclerenchyma tissue is responsible for adding mechanical strength to the plant body.

Question 16.
Which plant tissue is involved in ascent of sap?
Answer:
Xylem is involved in the ascent of sap.

Question 17.
Which plant tissue is involved in the transportation of food within the plant body?
Answer:
Phloem is involved in the transportation of food within the plant body.

Question 18.
Which type of cambium is also known as fascicular cambium?
Answer:
Vascular cambium is also known as fascicular cambium.

Question 19.
Which cell of phloem takes part in transportation of food?
Answer:
Sieve tubes take part in transportation of food.

Question 20.
Which cell is accompanied by companion cells?
Answer:
Companion cells accompany the sieve tube of plant cells.

Question 21.
Which is the only living member of xylem tissue?
Answer:
Xylem parenchyma is the only living member of xylem tissue.

Question 22.
Which meristem helps in increasing girth of the plant?
Answer:
Leteral meristem helps in increasing girth of the plant

Question 23.
Which cells of zylem exclusively provide mechanical support to the plant body?
Answer:
Xylem fibres exclusively provide mechanical support to the plant body.

Question 24.
Which tissue is predaminant in a hard woody plant part?
Answer:
Sclerenchyma tissue is predominant in a hard woody plant part.

Question 25.
What is the other name of cork cambium?
Answer:
The other name of cock cambium is phellogen.

Question 26.
What do companion cells do?
Answer:
Companion cells play supporting role in the conduction of food through sieve tubes.

Question 27.
Identify the main types of tissue present in pith of stem and husk of coconut.
Answer:
In the pith of stem, parenchyma tissue and in husk of coconut, sclerenclyma tissue is present.

Question 28.
What is chlorenchyma?
Answer:
The parenchyma tissue, carrying chloroplastids and acting as the site of photosynthesis is known as chlorenchyma.

Short Questions and Answers : (2 marks for each question)

Question 1.
Mention the correlation amongst cells, tissues, organs and body.
Answer:
Cells are the structural and functional unit of living body. Cells of same origin and function having similar or dissimilar structures constitute a tissue. One or more types of tissue when unite to perform a specific function, form a tissue system. Several tissue systems constitute an organ and various organs form a body.

Question 2.
For which type of plant tissue the phrase ‘Three in one’ is appropriate? Justify your answer.
Answer:
1. The phrase ‘Three in one’ is appropriate for the three types of meristem, based on their function.

2. Based on their function, meristems can be of three types-protoderm, procambium and ground meristem. Protoderm gives rise to epidermal layer of different plant parts, procambium gives rise to vascular tissues and ground meristem produces cortex, pith etc. Thus, the total plant body is made from these three meristems. So the statement is justified.

Question 3.
What do you mean by wood fibre? What is bast fibre?
Answer:
Wood fibre: Sclerenchyma fibre associated with xylem tissue is called wood fibre. It provides mechanical strength to the plant.

Bast fibre: Sclerenchyma fibre associated with phloem tissue is called bast fibre. It is responsible for making plant parts strong and also stores food.

Question 4.
What is the utility of tissues in multicellular organisms?
Answer:
Different utility of tissues in multicellular organisms are as follows-

• Tissue brings division of labour to increase efficiency.
• Tissues become organised to form organs and organ systems.
• Decreases the work load of individual cells.
• Chances of survival of these organisms increase due to higher efficiency and better organisation.

Question 5.
Why are some specific types of sclereids called stone cells?
Answer:
The deposition of lignin, cutin and suberin on the cell wall of some short and oval or spherical shaped sclereids, makes them hard like stones. The lumen of such cells are almost squeezed due to deposition. That is why, these special type of sclereids are called stone cells. Stone cells are responsible for mechanical support.

Question 6.
Mention the functions of cork cambium and vascular cambium.
Answer:

• Functions of cork cambium: It takes part in the growth of outer part of plant body beyond vascular bundle, to produce cortex and bark to replace ruptured epidermis.
• Functions of vascular cambium: It takes part in the formation of xylem and phloem within vascular bundle.

Question 7.
Mention the occurrence of parenchyma cells.
Answer:
The occurrence of parenchyma tissue is as follows-

• It is seen in the epidermis of all plant parts.
• It is present in ground tissue of plants including cortex, medulla and medullary rays.
• Mesophyll tissue of leaves is composed of parenchyma.
• It occurs in endosperm of seeds.

Question 8.
Where do you find xylem tissues?
Answer:
Components of xylem tissues are found in the following parts of plant-

• Tracheids and trachea occur in vascular bundle of root, stem and leaf.
• Xylem fibres are seen in vascular and cortex region of woody plants.
• Xylem parenchyma cells are present in vascular region of gymnosperms and dicot plants.

Question 9.
Where do you find collenchyma tissue?
Answer:
Collenchyma tissue is mainly found in the hypodermis of stem. Mid-rib and petiole the of leaves and peduncle of flowers are made up of collenchyma.

Question 10.
Mention the features of different types of collenchyma.
Answer:
Features of different types of collenchyma are as follows-

• Angular collenchyma cells have thickened corners.
• Lacunate collenchyma cells have thick walls near the intercellular spaces.
• Lamellate collenchyma cells have thick walls at the point of contact with adjacent cells.

Question 11.
Mention the different types of sclerenchyma, based on their features?
Answer:
Features of different types of sclerenchyma are as follows-

• Sclerenchyma fibres are long and narrow cells with pointed ends.
• Sclereids are broad with thick walled cells which occur singly or in small groups.

Question 12.
Where do you find sclerenchyma tissue in a plant?
Answer:
Components of sclerenchyma are found in the following parts of plant-

• Sclerenchyma fibres are present in the hypodermis, cortex, vascular bundles and pericycle.
• Sclereids are found in seed coats.

Question 13.
Mention the differences between prokaryotic and eukaryotic cells.
Answer:
Differences between prokaryotic and eukaryotic cell

Question 14.
Distinguish between meristematic tissue and permanent tissue.
Answer:

Feature	Meristematic tissue	Permanent tissue
1. Nature	Always living	Living or dead
2. Cell wall	Very thin and soft	Comparatively thick and rigid
3. Cytoplasm	Dense and spread all over the cell	Reduced as primordial utricle or totally absent
4. Vacuoie	Absent or very small	Very large
5. Divisibility	Divisible	Indivisible

Question 15.
Distinguish between simple permanent tissue and complex permanent tissue.
Answer:

Feature	Simple permanent tissue	Complex permanent tissue
1. Ceil types	Composed of similar types of cells	Composed of different types of cells
2. Cell wall	Thin, evenly or unevenly thickened	Evenly thickened
3. Vascular bundle formation	Does not form vascular bundle only helps to form it	Directly takes part in vascular bundle formation
4. Function	Formation of plant body, synthesis and storage of food	The absorbed materials from the roots are transported throughout the plant body

Question 16.
Distinguish between xylem and phloem.
Answer:

Feature	xylem	Phloem
1. Structural components	Tracheid, trachea, xylem parenchyma and xylem fibre; except xylem parenchyma, other components are dead	Sieve tube, companion cell, phloem parenchyma and phloem fibre; except pholem fibre, other components are living
2. Elements for transportation	Tracheid and trachea	Sieve tube
3. Direction of transportation	Against gravity	Transportation occurs irrespective of gravity
4. Function	Ascent of sap	Transportation of food

Question 17.
Distinguish between tracheid and trachea.
Answer:

Features	Sieve tube	Companion cell
1. Nucleus	Absent	Present
2. Shape	Cylindrical	Lens shaped
3. Cell plate	Porous, produces sieve like structure	Intact, no pore can be seen
4. Function	Transportation of food	Storage of food and helping in transportation of food through sieve tube

Question 18.
Distinguish between xylem fibre and phloem fibre.
Answer:

Features	Sieve tube	Companion cell
1. Nucleus	Absent	Present
2. Shape	Cylindrical	Lens shaped
3. Cell plate	Porous, produces sieve like structure	Intact, no pore can be seen
4. Function	Transportation of food	Storage of food and helping in transportation of food through sieve tube

Question 19.
Distinguish between xylem fibre and phloem fibre.
Answer:

Features	Xylem fibres	Phloem fibres
1. Occurrence	Sclerenchyma cells present in xylem	Sclerenchyma cells present in phloem
2. Shape	Narrower lumen, ends tapered to a point	Wider lumen, ends are blunt
3. Wall thickness	More thickened due to lignification	Less thickened, either lignified or non-lignified
4. Rigidity	More rigid	Comparatively flexible

Question 20.
Distinguish between trachea and seive tube.
Answer:

Features	Trachea	Sieve tube
1. Nature of cell	Dead	Living
2. Sieve plate	Absent	Present, perforations clogged with callose
3. Cell wall	Thickened with secondary thickening of lignin	Comparatively thin, primary wall lignified
4. Function	Ascent of sap against gravity	Transportation of food occurs irrespective of gravity

Long Questions and Answers : (5 marks for each question)

Question 1.
What is meant by tissue? How plant tissues can be classified into different types?
Answer:
Tissue
Tissue is the assemblage of a number of structurally similar or dissimilar cells having same origin and function.
Classification of different plant tissues:

Question 2.
What is meant by meristem or meristematic tissue? Describe the characteristic features of the meristematic tissue with a simple diagram.
Answer:
Meristem or meristematic tissue

Meristems or meristematic tissues are cells or group of cells that are capable of undergoing cell division.

• Cells are living, undifferentiated, polygonal, spherical or oval in shape.
• Cells are densely packed and without intercellular spaces.
• Cell wall is thin, made up of cellulose.
• Nucleus is large and distinct.
• Cytoplasm is dense, vacuoles generally absent.
• The cells are capable of undergoing cell division.

Question 3.
Describe the distribution of different meristematic tissues.
Answer:
Distribution of meristematic tissues:
Based on occurrence, meristematic tissues can be sub-divided into three types, which are as follows-

1. Apical meristem: It occurs at the tip of roots and shoots. This tissue helps the plant to grow in length.

2. Intercalary meristem: It occurs near the nodes of growing shoots, in between two layers of permanent tissues. This makes the young internodes longer and also helps in the growth of leaves.

3. Lateral meristem: It occurs along the lateral position of roots and stems of higher plants. It divides laterally and makes the plant thicker. It is of two types

• Vascular cambium (fascicular cambium): It occurs within vascular bundle to form new xylem and phloem.
• Cork cambium (phellogen): It occurs outside vascular bundle and takes part in the growth of outer layers of the stem and root.

Question 4.
What is meant by permanent tissue? Mention the characteristic features of permanent tissues.
Answer:
Permanent tissues.
The plant tissues in which cells have lost their capability of undergoing cell division are known as permanent tissues.

Characteristic features of permanent tissue:
The characteristic features of permanent tissue are as follows-

• Cells of these tissues do not divide and have no role in plant growth.
• Cells are differentiated into definite size, shape, structure and function.
• Cells have larger vacuoles. Cell walls may be thin or thick. Often ornamentations are seen on cell wall. Intercellular spaces are often present.
• These tissues comprise of either dead or living cells. In living cells, protoplasm is reduced with smaller nucleus.
• These tissues are involved in protection, support, transportation or secretion. Metabolic rate is slower in comparison to meristematic cells.

Question 5.
Describe the characteristic features of parenchyma tissue with simple diagram. Mention its functions in a plant body.
Answer:
Characteristic features of parenchyma tissue

The characteristic features of parenchyma tissue are as follows:

• Cells are living and thin walled, almost equal in size and shape.
• Cells are loosely packed with distinct intercellular spaces.
• Vacuoles are large. Cytoplasm becomes peripheral, forming primordial utricle with a distinct nucleus.

Functions of parenchyma tissue:
The functions of parenchyma tissue are as follows-

• Simple parenchyma cells occur in the ground tissue and store food.
• Aerenchyma maintains buoyancy in floating and submerged aquatic plants.
• Chlorenchyma takes part in photosynthesis.
• Idioblasts store mineral crystals, oil, excretory matter etc.
• Parenchyma allows movement of gases and gaseous exchange because of the presence of intercellular spaces in it.
• As epidermis or epiblemma, parenchyma protects all plant parts.

Question 6.
Describe the characteristic features of collenchyma tissue with diagram. Mention the function of this tissue.
Answer:
Characteristic features of collenchyma tissue

The characteristic features of collenchyma tissue are as follows-

• Cells are living and are of almost identical size. They are cylindrical, but in cross-section appear polygonal.
• Cell wall is made up of cellulose, hemicellulose and pectin, unevenly thickened at the corners.
• Intercellular space is reduced.
• Vacuole is large. Cytoplasm present as primordial utricle. Chloroplast may be present.

Functions of collenchyma tissue
The functions of collenchyma tissue are as follows-

• Provides mechanical strength.
• Provides flexibility to plant parts and Labelled diagram of collenchyma tissue prevents from breaking.
• This type of tissue helps to store food.
• It also carries out photosynthesis.

Question 7.
Describe the characteristic features of scierenchyma tissue with diagram. Mention the functions of this tissue.
Answer:
Characteristic features of sclerenchyma tissue

The characteristic features of sclerenchyma tissue are as follows-

• Cells are dead when mature, devoid of protoplasm and have narrow lumen.
• Cells are without inter-cellular space.
• Cell wall is evenly thickened and highly lignified.
• At some points, pits are present on the cell wall.
• Some cells are thin, elongated and pointed. These are called sclerenchyma fibres. Some are wide with very thick cell wall, which are called sclereids.

Functions of sclerenchyma tissue
The functions of sclerenchyma tissue are as follows-

• Provides mechanical strength.
• Makes the plant parts rigid.
• Sclereids especially form tough seed coat of legume fruits and endocarp of drupe.
• This tissue also protects plant parts from getting wet.

Question 8.
Name the componants of xylem. Describe the characteristic features of these components.
Answer:
Components of Xylem

Xylem has four typical components, these are tracheid, tracheae or vessels, xylem parenchyma and xylem fibres.

Characteristic features of xylem components
The characteristic features of xylem components are as follows-

• Tracheids are dead, elongated cells with pointed ends. Uneven lignified thickening of walls create different patterns. Pits are present in the cell wall. These cells take part in water transportation through the unthickened parts.
• Vessels or tracheae are long, tubular dead cells without end walls. Lumen is wider than in tracheids. The wall of the vessels possess many pits. These cells also carry sap. Numerous cells are arranged in a row to form long continuous vessels.
• Xylem fibres are dead cells, very thin & long with pointed ends. Cell wall is thick with a narrow lumen. These cells provide mechanical strength and rigidity to the plant body.
• Xylem parenchyma is the only living member of the xylem tissue. It has thin cell wall and it contains protoplasm.

Question 9.
Name different components of phloem. Describe the characteristic features of these components.
Answer:
Components of phloem

Phloem has four typical components, these are sieve tube, companion cell, phloem parenchyma and phloem fibre.

Characteristic features of phloem components
The characteristic features of phloem components are as follows-

• Sieve tubes are living cylindrical cells with perforated end walls, called sieve plates. Nucleus is absent in matured cells. Several sieve tubes are arranged in a row forming a long tube. These help in transportation and storage of food.
• Companion cells are lens-shaped cells with prominent nucleus and dense cytoplasm. They are present on either side of sieve tube. These help sieve tube in tranporation of food.
• Phloem parenchyma has granular cytoplasm and thin cell wall made up of cellulose. This component of phloem stores organic and ergastic materials.
• Phloem fibre is the only non-living component. It is elongated with lignified wall. Pits are present in the cell wall. Fibres provide mechanical support to plant parts.

Question 10.
What is sclerenchyma fibre? Where does it occur? Give a brief description of its structure.
Answer:
Sclerenchyma fibre
Long and fine sclerenchyma cells, with pointed ends and pitted wall, are known as sclerenchyma fibres.

Occurrence of sclerenchyma cells
Sclerenchyma cells occur in the hypodermis and pericycle of stem. These are seen in vascular bundle and bundle cap of dicot plants.

Structure of sclerenchyma fibres
The structure of sclerenchyma fibres is described as follows-

• Sclerenchyma fibres are very fine and long with two pointed ends.
• Cells are without intercellular spaces and are compactly arranged sidewise to form bundle.
• Cell wall is evenly thickened with bordered pits and lumen is narrow.
• Cells are dead and appear polygonal in cross-section.
• The sclerenchyma fibres occurring in xylem are called wood fibres. These fibres, when occur in phloem are called bast fibres.

Question 11.
What are trachea or vessels? Give a brief description of their structure. Mention the occurrence and functions of trachea.
Answer:
Tracheae or vessels:
Tracheae or vessels are the non-living, elongated, tubular xylem cells having highly lignified and evenly thick cell wall with bordered pits.

Structure of tracheae or vessels:
The structure of tracheae is as follows-

• These cells are dead, long and tubular in shape with completely or partially open ends.
• The wall is lignified with bordered pits. Ornamentations are often found on the wall due to uneven thickening.
• The lumen is the widest amongst all xylem components.
• Several tracheal cells remain arranged one after another to form a continuous tube due to the dissolution of end walls.

Occurrence of tracheae or vessels
These xylem components occur in all angiosperms and a gymnosperm named Gnetum.

Functions of trachea
The functions of trachea are as follows-

• It transports sap from root to leaves.
• Trachea provides mechanical support to the plant body.

Question 12.
What is xylem parenchyma? Give a brief description of its structure. Mention the occurrence and functions of xylem parenchyma.
Answer:
Xylem parenchyma
The only living cell of xylem with protoplasm, guarded by thin, cellulose-rich cell wall, is known as xylem parenchyma.

Structure of xylem parenchyma
The structure of xylem parenchyma is as follows –

• These are living cells with cytoplasm and small nucleus inside.
• Cell wall is thin and composed of cellulose.
• The cells are almost isodiametric and lateral walls have few simple pits.

Occurrence of xylem parenchyma
Xylem parenchyma is present in the vascular bundle of all angiosperms and most of the gymnosperms, except pines.

Functions of xylem parenchyma
The functions of xylem parenchyma are as follows-

• It helps in transportation of sap and also helps in lateral transportation.
• It stores nutrients like carbohydrates, fats and excretory matters like tannin, inorganic crystals etc.

Question 13
What are xylem fibres? Give a brief description of their structure. Mention the occurrence and
functions of xylem fibres.
Answer:
Xylem fibres
The dead and fine sclerenchyma cells of xylem are known as xylem fibres.

Structure of xylem fibres
The structure of xylem fibres is as follows-

• Xylem fibre cells are dead, very fine with pointed ends.
• Cells have very narrow lumen.
• Cell wall is very thick due to heavy lignification and rigid with both simple and bordered pits.
• Fibres are to two types-libriform fibre and tracheid fibre.

Occurrence of xylem fibres
Xylem fibres are present in vascular bundle of all angiosperms and most of the gymnosperms, except pines.

Functions of xylem fibres
The functions of xylem fibres are a follows-

• These provide mechanical support to plant body.
• These also store food material and certain excretory matters.

Question 14.
What is sieve tube? Give a brief description of its structure. Mention the occurrence and functions of sieve tubes.
Answer:
Sieve tube : Living elongated tubular phloem cell with sieve plates at two terminal ends and cytoplasm without nucleus is known as sieve tube.

Structure of sieve tube

The structure of sieve tube is as follows-

• Sieve tubes are tubular in shape, arranged longitudinally one after another to form a continuous pipe.
• The matured cells have cytoplasm but no nucleus inside.
• The wall is thin and composed of cellulose.
• The two terminal walls are well perforated and are called sieve plates.
• Connection between two sieve cells are made by cytoplasmic strands through sieve pores.

Occurrence of sieve tubes
Sieve tubes are present in pteridophytes and all flowering plants.

Functions of sieve tubes
The functions of sieve tubes are as follows–

• These help in transportation of food.
• These also occasionally store food.

Question 15.
What are companion cells? Give a brief description of their structure. Mention the accurreace and functions of companion cells.
Answer:
Companion cells : The living, nucleated, lens-shaped cells typically present at two sides of a sieve tube are known as companion cells.

Structure of companion cells
The structure of companion cells is as follows –

• The cells are living, full of dense cytoplasm and with a distinct nucleus inside.
• The cells have thin wall, made up of cellulose and appear triangular in cross-section.
• Laterally, these cells are lens-shaped.
• These cells keep a close association with the sieve tube through pits and plasmodesmata on lateral wall.

Occurrence of companion cells
Companion cells occur in phloem of all angiosperms and in a single gymnosperm, called Gnetum sp.

Functions of companion cells
The functions of companion cells are as follows –

• These help in transportation of food through sieve tube.
• These also store carbohydrate and help in lateral transport.

Question 16.
What is phloem parenchyma? Give a brief description of its structure. Mention the occurrence and functions of phloem parenchyma.
Answer:
Phloem parenchyma : Thin-walled, living, cylindrical cell of phloem tissue is known as phloem parenchyma.

Structure of phloem parenchyma
The structure of phloem parenchyma is as follows-

• The cell wall is thin and made up of cellulose. Rarely lignified and pitted.
• Shape of the cells are elongated, cylindrical and radially arranged with the plant axis.
• Cytoplasm of these cells stores starch, resin, tannin etc.

Occurrence of phloem parenchyma
It is seen in all dicot plants but monocot plants never possess phloem parenchyma. Pteridophytes and gymnosperms also have these cells in phloem.

Functions of phloem parenchyma
The functions of phloem parenchyina are as follows-

• It helps in food transport.
• It stores different organic matter and excretory substances.
• It helps in lateral transport of organic food matter.

Question 17.
What is phloem fibre? Give a brief description of its structure. Mention the occurrence and functions of phloem fibres.
Answer:
Phloem fibre
Phloem fibre is the only non-living component of phloem with thin, elongated shape and two pointed ends.

Structure of phloem fibre
The structure of phloem fibre is as follows-

• These cells are non-living, with very fine and hollow lumen.
• The cells are long with pointed ends.
• Cell wall is thick, well lignified and commonly have simple pits.
• The cells remain arranged one after another along the length.
• Fibres are overlapped above one another to form bundle.

Occurrence of phloem fibres
Phloem fibres are present in angiosperms only.

Functions of phloem fibres
The functions of phloem fibres are as follows-

• These provide mechanical support to the plant body.
• These also store food matter like starch.

Question 18.
Compare the characteristic features of parenchyma, collenchyma and sclerenchyma.
Answer:
Comparison among parenchyma, collenchyma and sclerenchyma

Features	Parenchyma	Coilenchyma	Sclerenchyma
1. Nature	Living	Living	Non-living
2. Cell wall	Evenly thick	Unevenly thick	Evenly thick
3. Shape of cells	Spherical or oval	Elongated, polygonal in cross-section	Elongated and polygonal
4. Main component of cell wall	Cellulose	Cellulose and hemicellulose	Lignin, cutin, suberin
5. Inter-cellular space	Present	May or may not be seen	Absent
6. Ornamentation on cell wall	Absent	Absent	Absent
7. Angular thickening of ceil wall	Absent	Present	Absent
8. Function	Synthesise and store food	Synthesise food and provide mechanical support	Provide mechanical support

 

Detailed explanations in West Bengal Board Class 9 Life Science Book Solutions Chapter 2.2 Cell offer valuable context and analysis.

WBBSE Class 9 Science Chapter 2.2 Question Answer – Cell

Very Short Questions and Answers : (1 mark for each question)

Question 1.
What do you mean by cell organelles?
Answer:
The intracellular components of a cell, which take part in different cellular functions, are called cell organelles.

Question 2.
Which is denoted as the structural and functional unit of life?
Answer:
Cell is denoted as the structural and functional unit of life.

Question 3.
Which part of a cell acts as the site of different cellular reactions?
Answer:
Protoplasm acts as the site of different cellular reactions

Question 4.
Which cell organelle is present in between cell wall and protoplasm of a plant cell?
Answer:
Cell membrane is present in between cell wall and protoplasm of a plant cell.

Question 5.
Besides cytoplasm and nucleus, which is another basic cellular component, present in all living cells?
Answer:
Besides cytoplasm and nucleus, cell membrane is another basic cellular component, present in all living cells.

Question 6.
Which component of cell membrane behaves like a fluid?
Answer:
The lipid bi-layer of cell membrane behaves like a fluid.

Question 7.
Which type of proteins in the cell membrane are called intrinsic proteins?
Answer:
The protein molecules, which remain submerged in the lipid bi-layer of cell membrane, are called intrinsic proteins.

Question 8.
Which type of proteins in the cell membrane are called extrinsic proteins?
Answer:
The protein molecules, which remain attached to the surface of the lipid bi-layer of cell membrane, are called extrinsic proteins.

Question 9.
Name the rigid, thick and non-living protective layer present outside the plasma membrane of bacterial and plant cells.
Answer:
The rigid, thick and non-living protective layer, present outside the plasma membrane of bacterial and plant cell, is known as cell wall.

Question 10.
Who proposed the famous ‘Unit Membrane Model’ of cell membrane?
Answer:
Scientist Robertson proposed the ‘Unit Membrane Model’ of cell membrane.

Question 11.
What is cytoplasm?
Answer:
Cytoplasm is the translucent, homogeneous and amorphous matrix of a living cell, present in between the cell membrane and the nuclear membrane.

Question 12.
How do different intracellular organelles remain evenly distributed within the cell?
Answer:
Continuous flow of cytoplasm distributes different intracellular organelles evenly within the cell.

Question 13.
Which portion of protoplasm has the maximum density?
Answer:
Within protoplasm, nucleus has the maximum density.

Question 14.
Mention a similarity between matured RBC of human blood and sieve tube of a mango tree.
Answer:
Both matured RBC of human blood and sieve tube of a mango tree are devoid of nucleus.

Question 15.
What is the name of the densest part of a nucleus?
Answer:
The densest part of a nucleus is called nucleolus.

Question 16.
Name the matrix, where DNA and RNA are synthesised within an eukaryotic cell.
Answer:
DNA and RNA are synthesised within the nucleoplasm of an eukaryotic cell.

Question 17.
Which membrane separates cytoplasm and nucleoplasm?
Answer:
Nuclear membrane separates cytoplasm and nucleoplasm.

Question 18.
Which cell organelies maintain direct contact with nuclear membrane?
Answer:
Endoplasmic reticula and ribosomes maintain direct contact with nuclear membrane.

Question 19.
How do different larger intracellular molecules move in and out through nuclear membrane?
Answer:
Different larger intracellular molecules move in and out through the pores of nuclear membrane.

Question 20.
What is the name of the inward projections of the inner membrane of mitochondria?
Answer:
The inward projections of the inner membrane of the mitochondria are called cristae.

Question 21.
Which cell organelle is called the ‘power house’ of a cell?
Answer:
Mitochondrion is called the ‘power house’ of a cell.

Question 22.
Which type of plastid is present in the cells of leaves and tender twigs of green plants?
Answer:
Chloroplastid is present in the cells of leaves and tender twigs of green plants.

Question 23.
Which type of plastid is present in the cells of carrot root?
Answer:
Chromoplastid is present in the cells of carrot root.

Question 24.
Which type of plastid is present in the cells of potato?
Answer:
Leucoplastid is present in the cells of potato.

Question 25.
Which cell organelle is directly involved in photosynthesis in green plants?
Answer:
Chloroplastid is directly involved in photosynthesis in green plants.

Question 26.
Which cell organelle is involved in cellular respiration?
Answer:
Mitochondrion is involved in cellular respiration.

Question 27.
Which membrane-less cell organelle is involved in protein synthesis within the living cell?
Answer:
Ribosome is the membrane-less cell organelle, involved in protein synthesis within a living cell.

Question 28.
Which structural components constitute a Golgi complex?
Answer:
Flat sac-like cisternae, small spherical vesicles, large saccular vacuoles and fine connecting tubules constitute the Golgi complex.

Question 29.
Which component of Golgi apparatus appears like flat sac?
Answer:
Cisterna of Golgi apparatus appears like flat sac.

Question 30.
What is the full form of GERL system?
Answer:
The full form of GERL system is Golgi Endoplasmic Reticulum Lysosome system.

Question 31.
Which structural elements constitute an endoplasmic reticulum?
Answer:
Wide flat, sac-like cisternae, long, branched and tube-like structures and tiny spherical vesicles constitute endoplasmic reticulum.

Question 32.
Which type of endoplasmic reticulum carries ribosomes?
Answer:
Rough endoplasmic reticulum carries ribosomes.

Question 33.
Which single membrane-bound cell organelle takes part in intracellular digestion?
Answer:
Lysosome is the single membrane-bound cell organelle which takes part in intracellular digestion.

Question 34.
Which cell organelle stores food particles within Amoeba?
Answer:
Food vacuoles store food particles within Amoeba.

Question 35.
Which cell organelle maintains the turgidity of a plant cell?
Answer:
Vacuoles maintain the turgidity of a plant cell.

Question 36.
Which macromolecule is involved in the formation of a polyribosome chain?
Answer:
RNA molecule is involved in the formation of a polyribosome chain.

Question 37.
Which are the structural constituents of a centriole?
Answer:
Protein microtubules are the structural constituents of a centriole.

Question 38.
What constitutes a microtubule?
Answer:
Several fine, rod-shaped protein microfilaments constitute a microtubule.

Question 39.
Which is the only cell organelle present in a prokaryotic cell?
Answer:
The only cell organelle present in a prokaryotic cell is ribosome.

Question 40.
Name a prokaryotic and an eukaryotic organism.
Answer:
Bacteria is an example of a prokaryotic and Amoeba is the example of an eukaryotic organism.

Question 41.
Which cell organelle is present only in animal cell?
Answer:
Centrosome is present only in animal cell.

Question 42.
Name a photosynthetic organism with centrosome.
Answer:
Chlamydomonas is a photosynthetic organism with centrosome.

Question 43.
Name a unicellular organism with plastid.
Answer:
Euglena is a unicellular organism which has plastid in its cytoplasm.

Question 44.
Which cell organelle is also known as chondriosome?
Answer:
Mitochondrion is also known as chondriosome.

Question 45.
Which cell organelle is also known as lipochondrion?
Answer:
Golgi body is also known as lipochondrion.

Question 46.
What is meant by the term monosomes?
Answer:
Freely scattered ribosomes, present in prokaryotic cells, are known as monosomes.

Question 47.
Which cells of higher plants do not possess cell walls?
Answer:
Germ cells (male and female gametes) of higher plants do not possess cell walls.

Question 48.
Which is the largest cell presert on earth?
Answer:
Ostrich egg is the largest cell (170mm x 135mm ) present on earth.

Question 49.
Which cell organelle acts as the hub of several microtubules?
Answer:
Centrosome acts as the hub of several microtubules.

Question 50.
Which two cell organelles are involved in intracellular digestion of food?
Answer:
Vacuole and lysosome take part in intracellular digestion of food.

Question 51.
Which double membrane-bound cell organelles are present exclusively in plant cells?
Answer:
Plastids are the double membrane-bound cell organelles, present exclusively in plant cells.

Question 52.
Which is the longest cell in human body?
Answer:
The longest cell in human body is neuron or nerve cell.

Question 53.
Who discovered nucleus?
Answer:
Nucleus was discovered by Robert Brown.

Question 54.
What is the other name of Golgi body?
Answer:
Golgi body in animal cell is also known as dictyosome in plant cell.

Question 55.
Name the yellow coloured plastid present in plants.
Answer:
Xanthoplast is the yellow coloured plastid present in plants.

Short Questions and Answers : (2 marks for each question)

Question 1.
What is a cell? Name an organism, which is made up of a single cell.
Answer:

• A cell is the structural and functional unit of life, composed of a mass of protoplasm, bounded by a thin, elastic, lipo-protein membrane.
• Amoeba is a protozoa which is made up of a single cell.

Question 2.
What are cell organelles? How do cell organelles help a cell to organise its life processes?
Answer:
All components, either membrane-bound or without membrane, performing specific and individual functions within a cell, are called the cell organelles.

Within a living cell, all different organelles perform their specific functions in a concerted manner. By this process, different cell organelles help a cell to organise its life processes.

Question 3.
What is meant by cell membrane? Which are the main structural components of a cell membrane?
Answer:

• Cell memberane: Cell membrane is a thin, transparent, delicate, flexible, living and selectively permeable sheath that bounds the protoplasm.
• Structural component: Proteins and lipids are the main structural components of a cell membrane. A few carbohydrate chains often remain attached to it.

Question 4.
What is phagocytosis?
Answer:
Phagocytosis is a process of cellular ingestion, in which cell membrane of certain animal cells in-folds to engulf tiny food particle. Example-In Amoeba food is ingested by phagocytosis.

Question 5.
What is phagosome?
Answer:
In phagocytosis, cell membrane infolds to engulf a food particle. This folding, along with food particles detaches from the cell membrane and enters the cytoplasm as a food vacuole. This food vacuole is known as phagosome.

Question 6.
What are microvilli? Mention their functions.
Answer:

• Microvilli: Cell membrane of some animal cells projects numerous minute finger-like projections along its periphery, these are called microvilli.
• Function: Microvilli increase cell surface area to help cellular absorption.

Question 7.
Why is pinocytosis called ‘cell drinking’?
Answer:
During pinocytosis, the liquid food materials enter the cell through the cell membrane, forming an invagination and then remain suspended within vesicles. That is why, pinocytosis is called cell drinking

Question 8.
What is pinosome?
Answer:
The vacuole, containing the liquid food material, which is formed by infolding of cell membrane within the cell during pinocytosis, is called pinosome.

Question 9.
What is glycocalyx?
Answer:
The thin layer, made up of polysaccharides and glycoproteins, present outside the cell membrane of bacterial cells and animal cells, is called glycocalyx.

Question 10
How does the cell wall form beyond the cell membrane of a plant cell?
Answer:
As a plant cell matures, it releases some polysaccharide materials outside the cell. These materials mainly include cellulose and hemicellulose, which slowly accumulate on the outer surface of the cell membrane and become hard to form the cell wall. Here, long cellulose chains form the structural framework and hemicellulose constitute the matrix of the cell wall.

Question 11.
Mention the functions of cell wall.
Answer:
Functions of cell wall are as follows-

• Cell wall provides a definite shape to the cell.
• It retains the cell structure during turgid condition and protects the cell from bursting due to osmotic pressure
• It protects the cell against internal or external pressure and mechanical injury.
• Being a freely permeable layer, it allows entry and exit of various molecules.

Question 12.
What are plasmodesmata? Mention its function.
Answer:

• Plasmodesmata: Plasmodesmata are the ultrafine cytoplasmic connection through the fine pits on the cell wall between two adjacent plant cells.
• Function: Inter-cellular transport is the main function of plasmodesmata.

Question 13
What are desmosomes? Mention its function.
Answer:

• Desmosomes: Desmosomes are protein plaques, developed in the cell membrane at the site of adhesion between two adjacent animal cells.
• Function: Inter-cellular transport between the cells.

Question 14.
What is hyaloplasm or cytosol? Mention its function.
Answer:

• Hyaloplasm: The colourless, viscous matrix of a living cell without the cell organelles, is called hyaloplasm or cytosol.
• Function; Hyaloplasm holds all cellular functions within it.

Question 15.
What is meant by ectoplasm and endoplasm?
Answer:

• Ectoplasm: The transparent, amorphous, homogeneous portion of a cytoplasm with low viscosity, present close to the cell membrane, is called ectoplasm.
• Endoplasm: The denser, granular, nonhomogeneous portion of cytoplasm with greater viscosity, present at the inner portion of a cell, is called endoplasm.

Question 16.
Mention the constituents of cytoplasm.
Answer:
In eukaryotic cells, cytoplasm contains matrix and different cell organelles. Matrix also contains 90% water and different types of organic and inorganic matters, such as nutrient molecules, different enzymes, mineral salts etc. Cytoplasm of prokaryotic cells contain all the above materials except membrane-bound cell organelles.

Question 17.
What is nucleus?
Answer:
The densest portion of protoplasm within the cytoplasm, bounded by a double membrane that carries chromosomes and controls all cellular activities, is called nucleus.

Question 18.
Name two protists with multiple nuclei.
Answer:
Paramoecium and Opalina are two protists with multiple nuclei.

Question 19
Name a plant cell with multiple nuclei and another without nucleus.
Answer:
Coenocytic hyphae of fungi have many nuclei while matured seive tube cells do not have nucleus.

Question 20.
Name a human cell which has multiple nuclei and one which has no nucleus.
Answer:
Voluntary muscle fibres have many nuclei, whereas, matured red blood cells do not have any nucleus in human.

Question 21.
What is nucleoplasm or karyolymph? Mention its functions.
Answer:

• The transparent, viscous and granular matrix of nucleus that holds chromatin reticula, is called nucleoplasm or karyolymph.
• Functions: Nucleoplasm acts as a site for synthesis of DNA and RNA. It also transports essential materials those involve in vital metabolism and cell function.

Question 22.
What are chromatin reticula? Mention its function.
Answer:

• Chromatin reticula: Chromatin reticula are the network of several fine thread-like structures, made up of DNA and histone protein, spread in the nucleoplasm of an eukaryotic cell.
• Function: DNA in chromatin material regulate protein synthesis and carry hereditary characteristics from parents to off-spring by giving rise to chromosomes before cell division.

Question 23.
What is chromosome? Mention its function.
Answer:

• Chromosome: Chromosome is a fine threadlike, self-replicating nucleoprotein structure, created from chromatin reticulum, inside the nucleus of eukaryotic cells, just before cell division.
• Function: Chromosomes contain genetic material DNA which in turn carries hereditary characters from one generation to the next.

Question 24.
What is meant by euchromatin and heterochromatin?
Answer:

• Euchromatin: The portions of chromatin reticula which are faintly stained with chromosomal stain, are called euchromatin.
• Heterochromatin: The portions of chromatin reticula which are intensely stained with chromosomal stain, are called heterochromatin.

Question 25.
What is gene? Where does it occur?
Answer:

• Gene: A gene is the specific portion of a DNA that commands a definite protein synthesis or carries a particular hereditary character from one generation to the next.
• Occurrence of gene: Gene occurs in DNA within chromosomes of eukaryotic cells. In prokaryotic cells it occurs in its naked DNA.

Question 26.
Why mitochondrion is called the power house of a cell?
Answer:
The main energy generating reactions of respiration, i.e. Krebs cycle and electron transport occurs in mitochondrion. Through these reactions, energy is liberated from food by oxidation and is stored in ATP. These ATP molecules are kept in mitochondrial matrix for future utilisation. Therefore, mitochondrion is called the power house of cell.

Question 27.
What does a nucleus do within a cell?
Answer:
Role of nucleus within a cell are as follows:

• Nucleus controls the overall activity of a living cell by regulating gene expression.
• It plays the main role in cell division.
• Nucleus carries hereditary features from mother cell to daughter cell through the DNA in chromosomes.

Question 28
Apart from energy generation, which other functions does mitochondrion perform in a cell?
Answer:
Different functions of mitochondrion are as follows-

• Mitochondria can synthesise amino acids to make their own protein as they have their own DNA.
• They help in the metabolism of fatty acids and synthesise cytochrome and many other biomolecules.

Question 29.
Mention the functions of different plastids.
Answer:
The functions of different plastids are as follows-

• Chloroplastids act as the site of photosynthesis in green plants.
• Chromoplastids help to develop the colour of flowers and fruits.
• Leucoplastids store food matters within plant cells in the form of starch.

Question 30.
What do you mean by primary lysosome? Define secondary lysosome.
Answer:

• Primary lysosome: Newly produced lysosomes are called as primary lysosomes. These lysosomes do not take part in digestion as their enzymes remain in granular form.
• Secondary lysosome: Secondary lysosomes actively take part in digestion in presence of different hydrolytic enzymes like protease, lipase, nucleosidase and phosphatase.

Question 31.
Why are lysosomes called suicidal bags?
Answer:
Any cell may show disturbances in cellular metabolism when it sustains an injury or becomes aged. Then the lysosomal vesicles within it bursts to release enzymes in the cytoplasm, which digest the cell within itself. Due to this, lysosomes are called suicidal bags.

Question 32.
State difference between cytoribosome and mitoribosome.
Answer:
Cytoribosomes are those ribosomes which are present in cell cytoplasm. It is 70S type in prokaryotic cell and 80 S type in eukaryotic cell. Mitoribosomes are the special type of ribosomes present in mitochondrial matrix. These are 55Stype.

Question 33.
Why ribosomes are called as protein factory of a cell?
Answer:
Within cytoplasm of all types of living cells, ribosomes directly take part in synthesis of protein with the help of mRNA and tRNA. Therefore, ribosomes are popularly called as the ‘protein factory of the cell.’

Question 34
What is the main function of centrosome? Why neurons are incapable of dividing?
Answer:
Main function of centrosome is to prepare spindle fibres during cell division. Centrosome within a neuron remains in inactive state and cannot form spindle fibre. Therefore, neurons are incapable of division.

Question 35.
What is meant by prokaryotic cell? Give example.
Answer:
The primitive cells without a true and organised nucleus and any of the membranebound cytoplasmic organelles are called prokaryotic cells. In these cells, genetic activities are controlled by a naked circular DNA. Example-Bacterial cell.

Question 36.
What is meant by eukaryotic cell? Give example.
Answer:
The cells with a true and various membranebound cell organelles, in which genetic activities are controlled by chromosome-borne DNA, are called eukaryotic cells. Example-Algal cell.

Question 37.
Mention three basic features of a plant cell.
Answer:
Basic features of a plant cell are as follows-

• Plant cells have dead cell wall beyond the cell membrane.
• These cells possess plastids in the cytoplasm.
• The vacuoles are large and lesser in number.

Question 38.
Mention the three basic features of an animal cell.
Animal:
Basic features of an animal cell are as follows-

• The outermost coating of an animal cell is a lipo-protein cell membrane.
• These cells possess centrosome in cytoplasm.
• Animal cells have many small vacuoles.

Question 39.
Why water turns red when beet root is boiled in it but remains unchanged when carrot is boiled in it?
Answer:
The pigment present in beet root is betacyanin which is water soluble. So when beet root is boiled in water, the pigment comes out of it and gets dissolved in water. On the other hand, carrot has a yellow pigment called carotene which is water insoluble. So when it is boiled in water, water colour remains unchanged.

Question 40.
Write down the functions of microtubules.
Answer:
Functions of microtubules are as follows-

• Microtubules form the cytoskeleton of the cell to give strength to it.
• These act as structural components of spermatozoa, flagella and cilia of cells, spindle fibres etc.
• They help to produce spindle fibre during cell division

Question 41.
What do you mean by GERL system?
Answer:
The three cell organelles, viz. Golgi complex (G), endoplasmic reticulum (ER) and lysosome (L) maintain a close functional relationship to establish sceretory system of a living cell. This secretory system is known as GERL system.

Question 42.
What are ergastic materials? Give an example.
Answer:
The non-living particles present in the cytoplasm of animal cells are together known as ergastic materials. These are produced during metabolic activities of cell. Example-Glycogen.

Question 43.
Mention two differences between centrosome and ribosome.
Answer:

Feature	Centrosome	Ribosome
1. Structure	Centrosome is composed of two centrioles which are made up of several protein microtubules	Ribosomes are composed of two sub-units which are made up of ribonucleoprotein particles
2. Function	It forms spindle fibres, cilia and flagella	It takes part in protein synthesis

Question 44.
Distinguish between ribosome and lysosome.
Answer:

Features	Ribosome	Lysosome
1. Occurrence	All types of cells	Animal cells
2. Membrane	Without membrane	Lined by single membrane
3. Location inside cell	Cytoplasm, surface of nuclear membrane and ER	Scattered in cytoplasm
4. Function	Protein synthesis	Intra-cellular digestion

Question 45.
Distinguish between cytoplasm and protoplasm.
Answer:

Features	Cytoplasm	Protoplasm
X. Occurrence	In the space between cell membrane and nuclear membrane of any living eukaryotic cell, in prokaryotic cells inside the cell membrane	Inside cell membrane of all living cells
2. Interrelation	It is the portion of protoplasm	It is not a portion of cytoplasm
3. Function	Acts as the site for all cellular functions except mRNA transcription and DNA replication in eukaryotic cells	Act as the site for all possible cellular functions

46.
Distinguish between phagocytosis and pinocytosis.
Answer:

Features	Phagocytosis	Pinocytosis
2. Received material	Solid organic matter or living cell	Water or any aquatic solution
3. Received structure	Phagosome	Pinosome
4. Example	Engulfing of pathogens by neutrophils and monocytes	Absorption of liquid digested food matters by intestinal mucosal cells

Question 47.
Distinguish between true nucleus and nucleoid.
Answer:

Features	True nucleus		Nucleoid
1. Occurrence	Eukaryotic cells		Prokaryotic cells
2. Size	Larger		Smaller
3. State of DNA	Compacted as chromosome by histone proteins		Nakedly suspended in the cytoplasm
4. Nuclear membrane	Present		Absent
5. Chromatin reticulum	Present		Absent

Question 48.
Distinguish between smooth endoplasmic reticulum and rough endoplasmic reticulum.
Answer:

Features	Smooth ER	Rough ER
1. Structural component	Tubule and vesicle	Cisternae and few tubules
2. Attachment with ribosome	No contact with ribosome	Ribosomes attach on outer surface
3. Location inside cell	In contact with cell membrane	In contact with nucleus
4. Function	Synthesis of lipids	Helping in protein synthesis

Long Questions and Answers : (5 marks for each question)

Question 1.
Briefly describe the structure of a mitochondrion along with a labelled diagram. Structure of mitochondria
Answer:
Structure of mitochondria

The structure of a mitochondrion is described as follow:

• Mitochondrion is a double membrane-bound, oval or rod-shaped cell organelle, present in all animal and plant cells.
• The inner membrane forms finger-like folds, called cristae, projecting towards the mitochondrial chamber.
• On the inner side of the inner membrane, several tiny tennis racket-like particles are present. These are called elementary particles or F₁ particles or F₀-F₁ particles or oxysomes.
• The outer membrane is smooth and contains spherical granules called Parson’s subunit, on its outer side.
• The inner chamber of mitochondria is filled with matrix (dense fluid). It contains a number of respiratory enzymes, proteins, lipids, ribosomes and circular DNA.
  

Question 2.
Briefly describe the structure of nucleus along with a labelled diagram.
Answer:
Structure of nucleus

The portion of protoplasm, which is deeply stained and with maximum density, is called nucleus. It is the most important organelle of the cell, containing the genetic material. It has four components.

• Nuclear membrane: It is a double-unit membrane structure. It is structurally similar to that of the cell membrane and separates nucleoplasm from the cytoplasm.
• Nuclear reticulum: It is made up of fine chromatin fibres that are composed of DNA and proteins. During cell division, it becomes visible as rod-shaped structures called chromosomes.
• Nucleolus: It is a dense granular structure that remains attached to chromatin fibres at a specific region, called nucleolar organiser region (NOR). Nucleolus is made up of RNA (ribonucleic acid).
• Nucleoplasm: It is a viscous granular sap, almost similar to that of cytoplasm. It acts as the site for synthesis of DNA and RNA.

Question 3.
Briefly describe the fluid mosaic model of plasma membrane. Mention the functions of it.
Answer:
Fluid mosaic model of cell membrane

The fluid mosaic model of plasma membrane is described as follows—

• [Plasma membrane is a thin, delicate, flexible, living and selectively permeable membrane. It separates the protoplasm from external environment.
• Singer and Nicholson (1972) proposed the most acceptable model for the structure of cell membrane. According to this model, the plasma membrane is composed of two very’ closely placed lipid layers, in which various protein molecules float in a mosaic pattern. For this reason, this model is popularly known as ‘fluid mosaic model;
• The protein molecules are of two types—extrinsic proteins (remain attached to the membrane surface) and intrinsic proteins (remain submerged in the lipid bi-layer).
• As the lipid layer is fluid in nature, the protein molecules are free to move. Some times, extrinsic proteins are attached with antenna-like carbohydrates, proteins or lipid molecules.

Functions of plasma membrane:
The functions of plasma membrane are as follows—

• It protects the cell against any external injury and repairs damages sustained by it.
• Transportation of all solvents and some selected solutes in and out of the cell, hence, it is called selectively permeable membrane.
• It helps to engulf tiny food particles and liquid droplets by the process of endocytosis. Waste matters of the cells are discharged by exocytosis.
• The plasma membrane also plays a pivotal role in protecting and maintaining the integrity of the cell by allowing specific substances to enter, while keeping the others out.

Question 4.
Briefly describe the structure of chloroplastid with a labelled diagram of it.
Answer:
Structure of chloroplastid

The structure of chloroplastid is described as follows—

• These are green coloured plastids, usually biconvex or planoconvex in shape.
• A double-unit, lipo-protein membrane defines its shape. The thin, fluid-filled space in between the outer and the inner membrane is known as periplastidial space.
• The inner chamber is wide and full of jelly-like matrix, called stroma. The inner chamber contains membrane-bound disc-like sacs, called thylakoids which are stacked to form granum.
• Grana remain interlinked by thin membranous strips, called stroma-lamellae. Chlorophyll molecules are stored within thylakoids, which form the site for photosynthesis.

Question 5.
Briefly describe the structure of Golgi body. Mention its function.
Answer:
Structure of Golgi body

The structure of Golgi body is described as follows—

• Golgi body is a cluster of single membrane- bound cisternae, small vesicles and large vacuoles.
• Cisternae are curved, flat tube-like sacs arranged in parallel manner. Cisternae remain associated with small vesicles by small, branched tubules. These components constitute the Golgi apparatus.
• The Golgi apparatus is basically made up of compartments consisting of two main networks, the convex face as C is Golgi Network (CGN) and the concave face as Trans Golgi Network (TGN). The convex face of Golgi apparatus maintains connection with ER by some tubules.
• Lysosomes are formed from the concave face of Golgi apparatus.

Function of Golgi body
The functions of Golgi body are as follows—

• It participates in secretion of enzymes, hormones, mucous etc.
• It helps in transportation of proteins, enzymes, hormones within and outside the cells.
• It helps in the production of complex sugar, glycoproteins and glycolipids and acts as ‘storage of food.’
• It helps in the formation of lysosomes and other cell-organelles.
• It helps in the formation of acrosome of sperm.

Question 6.
Briefly describe the origin and structure of cell wall.
Answer:
Origin of cell wall
In the cytokinesis phase of cell division, vesicles from endoplasmic reticulum and Golgi bodies are gathered and arranged at equatorial zone of plant cell. Later vesicles get attached with each other to form cell plate. This cell plate eventually gives rise to cell wall by depositing pectin.

Structure of cell wall
The cell wall occurs only in plant and bacterial cells. It is rigid, thick and non-living protective layer present outside the cell membrane. Cell wall has three layers which are as follows—

• Middle lamella: It is a jelly-like intercellular matrix, present in be adjacent cells. It is composed of calcium and magnesium pectate.
• Primary cell wall: The primary cell wall is the outermost layer of cell wall. It is comparatively thin, permeable and elastic, it is composed mainly of cellulose and hemicellulose.
• Secondary cell wall: This layer is situated in between the primary cell wall and cell membrane. This layer is mainly built by deposition of lignin, suberin, hemicellulose etc. from the cell. Therefore, its thickness increases with the age of the cell.

Question 7.
Briefly describe the occurrence, structure and functions of endoplasmic reticulum.
Answer:
Occurrence of endoplasmic reticulum:
ER is present in endoplasm of eukaryotic cells, extended from nuclear membrane to cell membrane.

Structure of endoplasmic reticulum:
It is a system of network made up of membrane-bound flat, sac-like structure cisternae, small spherical vehicles and narrow tube-like tubules. Cisternae and vesicles remain interconnected by the tubules. ER is of two types-

• Rough ER having ribosomes on its surface.
• Smooth ER having no ribosomes on its surface.

Functions of endoplasmic reticulum:
The functions of endoplasmic reticulum are as follows-

• It divides the cell into a number of compartments and helps in the formation of different other cell-organelles directly or indirectly like Golgi body, lysosome, etc.
• It acts as a cytoplasmic barrier between different bio-chemical reactions.
• Rough ER helps in synthesis and transportation of protein.
• Smooth ER takes part in synthesis of lipid.

Question 8.
Briefly describe the occurrence, structure and function of centrosome.
Answer:
Occurrence of centrosome
Centrosome occurs in the cytoplasm near the nucleus of eukaryotic animal cells as a non-membranous, star-shaped organelle.

Structure of centrosome
Centrosome consists of two main parts, i.e. centriole and centrosphere, which are described as follows—

• Centriole: Two closely placed small cylindrical structures called centrioles, arranged at right angles to each other, forms a centrosome or diplosome. Each centriole is composed of nine very fine protein tubules, called microtubules, held by a central hub.
• Centrosphere: Centrioles are surrounded by a transparent non-granular cytoplasmic layer, called centrosphere. Before cell division, microtubules radiate from the centrosphere like sunrays, these are called rays.

Functions of centrosome
The functions of centrosome are mentioned below.

• It forms spindle fibres during cell division and helps in chromosomal movement.
• It helps in the formation of structural component of flagella and cilia of cells and tail of spermatozoa.

Question 9.
Briefly describe the occurence, structure and function of vacuoles.
Answer:
Occurrence of vacuoles
Vacuoles of animal cells are small, numerous and are spread all over the cytoplasm. In plant cells, one or two big vacuoles occupy a large space inside the cell.

Structure of vacuole
The structure of vacuole is described below.

• Vacuoles are small to large, variously shaped sac-like structures, surrounded by a thin cytoplasmic lining, called tonoplast.
• The cavity of a vacuole remains filled with a liquid, called cell-sap.
• In older plants one or two very large vacuoles occupy most of the space inside a cell, leaving the protoplasm as a thin layer along the inner side of the cell membrane. This thin layer of protoplasm is called primordial utricle.

Functions of vacuole:

The functions of vacuole are mentioned below.

• Vacuoles maintain an equilibrium of pressure inside cytoplasm.
• Hydrostatic pressure (turgor pressure) inside vacuole keeps the herbaceous plants erect and helps them to grow in size.
• Contractile vacuoles remove unwanted materials from the cell.
• Phagocytic vacuole helps in feeding and digestion in some holozoic protists like Amoeba.

Question 10.
What is primordial utricle? How many types of vacuoles can be seen in living cell?
Answer:
Primordial utricle
In older plant cells, one or two very large vacuoles occupy most of the space inside a cell, pushing the protoplasm towards boundary. In this condition the protoplasm remains as a thin layer along the inner side of the cell membrane. This thin layer of protoplasm is called Primordial utricle.

Types of vacuoles
Living cells have following types of vacuoles-

• Food vacuole: Food remains stored in this type of vacuole.
• Water vacuole: Specially unicellular organisms store water in this type of vacuole.
• Gas vacuole: Sometimes unicellular organisms store gas in the vacuoles instead of water.
• Contractile vacuole: Protozoa like Amoeba store excretory substances in some vacuoles which can contract and expand and with this mechanism excretory materials are expelled from the cell.

Question 11.
Briefly deseribe the occurrence, structure and function of ribosome.
Answer:
Occurrence of ribosome
Ribosomes are present in cytoplasm of prokaryotic cells. These remain attached to surface of nuclear membrane and rough ER. Ribosomes are seen in chloroplastids and mitochondria.

Structure of ribosome
The structure of ribosome is decribed as follows:

• Each ribosome is built with a large spherical and a small oval sub-unit, held together by magnesium ion.
• In eukaryotic cell, the two sub-units respectively measure 60 S and 40 S, whereas in prokaryotic cells these are of 50 S and 30 S. here, ‘S’ indicates sedimentation coefficient or Svedverg’s unit.
• Ribosome contains 50% RNA and 50% histone protein.
• During proteinsynthesis many ribosome units are tied in a row by an mRNA chain, like a beaded string. This structure is known as polyribosome or polysome.

Functions of ribosome
The functions of ribosome are as follows-

• Ribosomes synthesise proteins with the help of mRNA and tRNA.
• It helps in metabolism of lipids.
• It also helps in transportation of synthesised proteins.

Question 12.
Mention three similarities and four dissimilarities between mitochondria and plastids.
Answer:
Similarities between mitochondria and plastids
Three similarities between mitochondria and plastids are as follows-

• Both mitochondria and plastids are double membrane-bound structures.
• Both of these cell organelles possess DNA and both are self-replicating.
• Both the cell organelles contain 70S (prokaryotic) type of ribosome.

Dissimilarities between mitochondria and plastids

Features	Mitochondria	Plastids
1. Occurrence	Present in all living eukaryotic cells	Present in cells of mesophyll tissue of green plants
2. Structure	Inner membrane is folded inwardly to form finger-like cristae	Inner membrane is smooth
3. Enzymes	Carry respiratory enzymes	Carry photosynthetic enzymes
4. Function	Acts as the reaction site for Krebs cycle of aerobic respiration	Acts as the reaction site for both light-dependent and light-independent phases of photosynthesis

Question 13.
Describe the structure of a prokaryotic cell.
Answer:
Structure of a prokaryotic cell

The structure of a prokaryotic cell is described as follows—

• Most of the prokaryotic cells are very tiny and range from 0.1p to 2.5p.
• An ideal prokaryotic cell has a distinct lipoprotein plasma membrane surrounding its protoplasm.
• A circular DNA constitutes a nucleoid, which carries out all hereditary’ and genetic functions. Chromosome and nuclear membrane are absent.
• The cytoplasm is devoid of any membrane-bound cell organelle.
  Food and ergastic materials remain suspended in it.
• The cell membrane infolds to form mesosome, which carries respiratory enzymes.
• Few lamellar structures carry photosynthetic pigments in the cells of Prokaryotic ceil autotrophic form.
• Smaller 70S ribosomes remain scattered in the cytoplasm.
• A prokaryotic cell may have flagella or cilia as locomotary organs.

Question 14.
Mention three similarities and four dissimilarities between Golgi body and endoplasmic reticulum.
Answer:
Similarities between Golgi body and endoplasmic reticulum:
Three similarities between Golgi body and endoplasmic reticulum are as follows—

• Both Golgi body and endoplasmic reticulum have single-layered membrane.
• Both have flat sac-like cisternae and tiny vesicles. Both of these organelles are involved in intra-cellular transportation.
• Both the organelles are involved in biosynthesis of different molecules like hormones and steroids.

Dissimilarities between Golgi body and endoplasmic reticulum
Answer:

Features	Golgi body	Endoplasmic reticulum
1. Occurence	Present in eukaryotic animal cell. In plant cell, they are named as dictyosome. They remain scattered throughout the cytoplasm	Present in all eukaryotic cell, it is continued from nuclear membrane and cell membrane
2. Structure	Cisternae have no connection in between, rather they are parallel to each other	Cisternae are interconnected by tubules to form a network
3. Ribosomes	Ribosomes have nothing to do with golgi body	Rough endoplasmic reticulum has several ribosomes attached to its surface
4. Function	Main functions are secretion of hormones, enzymes etc. and formation of lysosome	Main functions are formation of intracellular compartments and transportation of proteins and other cellular materials

Question 15.
Distinguish between cell membrane and cell wall.
Answer:
Differences between cell membrane and cell wall

Question 16.
Mention the differences between prokaryotic and eukaryotic cells.
Differences between prokaryotic and eukaryotic cell!
Answer:

Question 17.
Distinguish between a plant cell and an animal cell.
Differences between a plant cell and an animal cell
Answer:

Features	Prokaryotic cell	Eukaryotic cell
1. Size	Smaller (generally 0.1-10 y)	Larger (generally 10-100 ji)
2. Cell wall	Made up of peptidoglycan or muramic acid	Absent in animal cell and made up of mainly cellulose, hemicellulose, pectin and suberin
3. Nucleus	Without nuclear membrane and nucleolus	True membrane-bound nucleus present
4. Chromosome	True chromosome absent; Genetic material is a single, circular DNA molecule called the nucleoid	DNA and protein form true paired chromosome
5. Cell organelles	Membrane-bound cell organelles absent	Membrane-bound cell organelles (mitochondria, Golgi body, plastids, ER etc.) are present
8. Ribosomes	Smaller in size, 70S type, remain scattered in the cytoplasm	Larger in size, SOS type, some remain attached to nuclear membrane and rough ER, others remain scattered in the cytoplasm

Question 18.
Draw a labelled diagram of an eukaryotic plant cell.
Labelled diagram of an eukaryotic plant cell
Answer:

Question 19.
Draw a neat diagram of an eukaryotic animal cell and label different parts of it.
Labelled diagram of an eukaryotic animal cell
Answer:

Detailed explanations in West Bengal Board Class 9 Life Science Book Solutions Chapter 5.1 Ecology and Ecological Organisations offer valuable context and analysis.

WBBSE Class 9 Science Chapter 5.1 Question Answer – Ecology and Ecological Organisations

Very Short Questions and Answers : (1 mark for each question)

Question 1.
Who first coined the term ‘ecology’?
Answer:
Famous ecologist, Ernst Haeckel (1869), coined the term ‘ecology’.

Question 2.
Which level of ecology deals with the interaction of a species with the environment?
Answer:
Population level of ecology deals with the interaction of a species with the environment.

Question 3.
Which level of ecology deals with the interaction of two or more species?
Answer:
Community level of ecology deals with the interaction of two or more species.

Question 4.
Give an example of effect of light on plants.
Answer:
Long day plants (such as mustard, radish etc.) require light for more than 12 hours for flowering.

Question 5.
Which type of plants are adapted to survive in bright sunlight?
Answer:
Heliophytes, such as pine trees, are adapted to survive in bright sunlight.

Question 6.
Which type of plants are adapted to survive in low sunlight?
Answer:
Sciophytes, such as ferns, are adpated to survive in low sunlight.

Question 7.
In which physiological event, does the flowering of plants depend upon the span of daylight?
Answer:
In photoperiodism, flowering of plants depends upon the span of daylight.

Question 8.
Name some long day plants.
Answer:
Mustard, radish, tobacco etc. are long day plants.

Question 9.
Name some short day plants.
Answer:
Dahlia, cosmos, sugarcane, strawberry etc. are common short day plants.

Question 10.
Name some day neutral plants.
Answer:
Cucumber, tomato, cotton etc. are some day neutral plants.

Question 11.
Give an example of effect of humidity on plants.
Answer:
Increase in humidity reduces the rate of transpiration in plants.

Question 12.
Give an example of effect of temperature on plants.
Answer:
Reduction of temperature reduces the rate of flowering in certain plants such as tulip.

Question 13.
Give an example of effect of light on animals.
Answer:
Zooplanktons move towards the upper surface of the water bodies in presence of sunlight.

Question 14.
Give an example of effect of humidity on animals.
Answer:
In certain desert animals, like Moloch horridus, the skin possesses numerous hygroscopic spines to keep the body moist as much as possible.

Question 15.
Give an example of effect of temperature on animals.
Answer:
Due to extremely low temperature in polar regions, the size of polar bears are bigger compared to the bears of warmer region.

Question 16.
In which type of animals, very few sweat glands are found?
Answer:
In desert animals, number of sweat glands are very low.

Question 17.
In which geographical region, plants have less leaves and more spines?
Answer:
In desert, plants have less leaves and more spines.

Question 18.
In which region tall trees with needle-like leaves are found?
Answer:
Tall trees with needle-like leaves are seen in regions, where occasional snowfall occurs.

Question 19.
Name one component of population.
Answer:
Species is a component of population.

Question 20.
Name two factors that regulate population size.
Answer:
Natality and mortality are two factors that regulate population size.

Question 21.
Name two factors that increase population size.
Answer:
High natality and immigration increase population size.

Question 22.
Name two factors that decrease population size.
Answer:
High mortality and emigration decrease population size.

Question 23.
Members of which age group are predominant in a growing population?
Answer:
Members of lower age group are predominant in a growing population.

Question 24.
In a community, size of which trophic level increases with decrease in number of predators?
Answer:
In a community, size of primary consumer population increases with the decrease in number of predators.

Question 25.
Name one positive and one negative interspecific interaction.
Answer:
Commensalism is a positive and predation is a negative inter-specific interaction.

Question 26.
Give an example of symbiosis in the plant world.
Answer:
Lichen is an example of symbiosis in the plant world.

Question 27.
Name the inter-specific relation between orchid and mango tree.
Answer:
The inter-specific relation between orchid and mango tree is a type of commensalism.

Question 28.
Which type of symbiosis is noticed between Trychonympha and termites?
Answer:
Obligatory symbiosis is noticed between Trychonympha and termites.

Question 29.
Which type of relation is prevalent amongst various predators in a community?
Answer:
Various predators in a community carry on competition against each other.

Question 30.
What is hyperparasite?
Answer:
A parasite, that draws nutrition from another parasite, is called a hyperparasite.

Question 31.
What kind of interaction is competition?
Answer:
Competition is a negative-negative (- -) interaction.

Question 32.
What kind of interaction is predation?
Answer:
Predation is a positive-negative interaction.

Question 33.
Give two examples of positive-positive interaction.
Answer:
Examples of positive-positive interaction are mutualism and protocooperation.

Question 34.
What happens in commensalism?
Answer:
In commensalism, one individual is benefited and the other individual is neither benefited nor harmed.

Question 35.
Which is the ultimate source of energy in every ecosystem?
Answer:
Sun is the ultimate source of energy in every ecosystem.

Question 36.
Who acts as producer in any ecosystem?
Answer:
Green plants act as producer in any ecosystem.

Question 37.
Who acts as consumer in any ecosystem?
Answer:
All animals act as consumer in any ecosystem.

Question 38.
Who acts as decomposer in any ecosystem?
Answer:
Micro-organisms, such as bacteria, fungi etc. act as decomposer in any ecosystem.

Question 39.
Give two examples of phytoplanktons.
Answer:
Two examples of phytoplanktons are Chlamydomonas and Volvox.

Question 40.
Give two examples of zooplanktons.
Answer:
Two examples of zooplanktons are Cyclops and Daphnia.

Question 41.
Name two pelagic animals.
Answer:
Mosquito larvae and jellyfish are pelagic animals.

Question 42.
Give two examples of Necton.
Answer:
Fishes and whales are examples of Necton.

Question 43.
Give two examples of benthos.
Answer:
Corals and sea-anemones are examples of benthos.

Question 44.
What will happen if all the producers of any ecosystem are completely destroyed?
Answer:
If all the producers of an ecosystem are completely destroyed, the entire animal population of that ecosystem will be destroyed.

Question 45.
Name two plants that act as consumers.
Answer:
Dionaea sp. (venus flytrap) and Nepenthes sp. (pitcher plant) are two insectivorous plants that act as consumers. They feed on insects.

Question 46.
How much energy is transferred from one trophic level to the next in an ecosystem?
Answer:
10 % energy is transferred from one trophic level to the next in an ecosystem.

Question 47.
Who proposed the 10 % law of energy flow in an ecosystem?
Answer:
Famous scientist Lindeman, proposed the 10 % law of energy flow in an ecosystem.

Question 48.
Give an example of detritus food chain.
Answer:
Example of detritus food chain isEarthworm arrow Sparrow arrow Hawk.

Question 49.
Give an example of grazing food chain.
Answer:
Example of grazing food chain is-Grass arrow Grasshopper arrow Frog arrow Snake arrow Hawk.

Question 50.
Who are macro-consumers in any ecosystem?
Answer:
In an ecosystem, macro-consumers include all herbivores (cow, goat etc.) and all carnivores (cat, dog, tiger, lion etc).

Question 51.
Who are micro-consumers in any ecosystem?
Answer:
In an ecosystem, micro-consumers include all fungi and bacteria.

Question 52.
Give an example of terrestrial and aquatic ecosystem.
Answer:
Example of terrestrial ecosystem is forest ecosystem and example of aquatic ecosystem is pond ecosystem.

Question 53.
Name two nutrient cycle.
Answer:
Carbon cycle and oxygen cycle are two nutrient cycle.

Short Questions and Answers : (2 marks for each question)

Question 1.
What is meant by environment?
Answer:
All physical, living and non-living components surrounding the living organisms, which show direct or indirect impact on their behaviour, reproduction and life style, are collectively known as environment.

Question 2.
What is ecology?
Answer:
Ecology is the branch of science, dealing with study of interrelation amongst all physical, nonliving and living components of an environment.

Question 3.
What is ecosystem?
Answer:
Ecosystem is a functional unit of nature, where various living components interact with each other and with the non-living components, in a specific environment.

Question 4.
What is autecology?
Answer:
The branch of ecology dealing with the study of interrelation amongst different members of a single species (population) with each other and with the environment, is called autecology. Ecology of termites is an example of autecology.

Question 5.
What is synecology?
Answer:
The branch of ecology dealing with the study of interrelation amongst members of different species (community), residing in diverse environment, with each other and with the environment is called synecology. Ecology of a forest is an example of synecology.

Question 6.
Mention three environmental factors, which have direct impact on organisms at individual level.
Answer:
Light, relative humidity and temperature are three main environmental factors, which have direct impact on organisms at individual level.

Question 7.
What is photoperiodism?
Answer:
The physiological activity of various organisms depending upon the length of day or night is known as photoperiodism. For example, blooming and leaf abscission in plants and breeding and migration in animals, depend upon the relative length of light and dark periods.

Question 8.
What is meant by long day plant?
Answer:
The plants, that require longer span of day light for blooming, are called long day plants. Example-Mustard, Radish etc.

Question 9.
What is meant by short day plant?
Answer:
The plants, that require shorter span of day light for blooming, are called short day plants. Example-Rice, Cotton, Sugarcane, Dahlia etc.

Question 10.
Which physiological activities of plants are affected mainly by relative humidity?
Answer:
The rate of transpiration, water absorption and germination of seeds are some physiological activities of plants, which are directly affected by relative humidity.

Question 11.
How does environmental temperature affect biological activities of plants?
Answer:
Distribution of vegetation, rate of metabolism, blooming of flowers, transpiration etc. are various biological activities of plants, which are directly affected by environmental temperature.

Question 12.
Mention few examples of the impact of environmental temperature on animals.
Answer:

1. Sex ratio of rat flea and Daphnia are affected by temperature.
2. Hyla, the tree frog becomes darker in colour in higher temperature.
3. Body size of birds and mammals of cooler region becomes larger.
4. At higher temperature, metabolic rate becomes higher.

Question 13.
What is natality? Express natality by an equation.
Answer:
Natality: Natality or birth rate can be defined as, the ratio of total live births to total population in a specified community or area, over a specific period of time.

Expression: Natality is expressed as the number of live births per 1000 of the population per year. It is represented by the following equation -B = \(\frac{n d}{\mathrm{~N}}\) × 1000
where, B = birth rate or natality, N = total number of individuals in a population, nb = number of live births.

Question 14
What is mortality? Express mortality by an equation.
Answer:
Mortality: Mortality or death rate can be defined as, the ratio of total deaths to total population in a specified community or area, over a specific period of time.
Expression: Mortality is expressed as the number of deaths per 1000 of the population per year. It is represented as the following equation-
D = \(\frac{n d}{\mathrm{~N}}\) × 1000
where, D = Death rate or mortality, N = Total number of individuals in a population, nd = Number of deaths.

Question 15.
What is meant by absolute natality?
Answer:
The theoretical rate of increase of a population size in presence of all favourable factors and complete absence of any negative factor related to birth, is known as absolute natality.

Question 16.
What is meant by realized or ecological natality?
Answer:
The true rate of increase of a population size, in presence of all controlling factors (environmental pressure) acting on the birth of new members, is called realised or ecological natality.

Question 17.
Why is absolute natality higher than realized natality?
Answer:
In nature, different controlling factors restrict the reproductive process and increase foetal death. Therefore, the natality value never reaches that level as expected in ideal setup. That is why, absolute natality becomes higher than realized natality.

Question 18.
What is migration?
Answer:
Migration is the movement of animals or human beings, individually or in large group, from one place to another, temporarily or permanently, due to environmental or biological factors.

Question 19.
Why do animals migrate from one place to another?
Answer:
Animals migrate from one place to another due to seasonal food and water scarcity, temperature change, natural calamities like excessive rainfall or snowfall, population pressure and in search of good breeding place etc.

Question 20.
What is immigration? What is its impact on a population?
Answer:
Immigration: Immigration is the permanent inflow of a bulk of animals or human beings, from any other locality into a population.
Impact: Immigration increases the size of a population.

Question 21.
What is emigration? What is the impact of emigration on a population?
Answer:
Emigration: Emigration is the permanent exit of a bulk of animals or human beings of a population from their habitat to some other place.
Impact: Emigration reduces the size of a population.

Question 22.
What is meant by population density?
Answer:
Population density is the number of individuals of a population, residing in a unit area of their natural habitat. It can be expressed by the following equation -D = \(\frac{n d}{\mathrm{~N}}\),
where, D = Population density, N = No. of individuals of a population, A}= Area of the natural habitat.

Question 23.
What is population? What is population size?
Answer:
Population: Population is an aggregate of naturally interbreeding individuals inhabiting in same geographical area at a certain period of time.
Population size: Population size (usually denoted by N) is the number of individual organisms in a population.

Question 24.
What is carrying capacity?
Answer:
Carrying capacity of an ecosystem is the maximum population size of a given species that the environment can sustain indefinitely, by providing the necessary resources (food, water, habitat) available in the environment.

Question 25.
What is overpopulation?
Answer:
If the population size of a species exceeds the carrying capacity of the environment for that particular kind of species, then this unsustainable condition is known as overpopulation. Various factors like, increased natality, reduced mortality, increased rate of immigration or depletion of resources are responsible for overpopulation.

Question 26.
What is biotic community?
Answer:
Biotic community is a natural assemblage of a number of interacting populations that occupy the same geographical area, in a particular time.

Question 27.
Which types of interactions are commonly seen in a biotic community?
Answer:
Members of a biotic community are involved in various interactions. These are competition, predation, parasitism, cooperation etc.

Question 28.
What is meant by competition? Give example.
Answer:
Competition: Competition is a negative interaction amongst the members of same or different species in a population to obtain more of the limited natural resources (food, water, shelter) for survival.
Example: Lions compete for food with cheetah and hyena.

Question 29.
What is meant by predation? Give example.
Answer:
Predation: Predation is an inter-specific positive-negative interaction between prey and predators, where predator survives by feeding on the prey.
Example: Birds feed on insects. Snakes feed on rats and frogs.

Question 30.
What is meant by parasitism? Give example.
Answer:
Parasitism: Parasitism is a non-mutual, symbiotic, positive-negative interaction, where one organism is benefited at the expense of the other.
Example: Tapeworms (Taenia) draw nutrition from human (host) intestine. Dodder plants (Cuscuta) suck nutrients from phloem of the host plants.

Question 31.
What is meant by cooperation? Mention the types of cooperation.
Answer:
Cooperation: Cooperation is a positive interaction between two different species, where either both are benefited or one is benefited and the other remains unaffected.
Types: Cooperation is of three types

1. commensalism
2. mutualism
3. protocooperation.

Question 32.
What is meant by commensalism? Give example.
Answer:
Commensalism: Commensalism is a positiveneutral inter-specific interaction, where one member is benefited but the other remains unaffected.

Example: Orchids (epiphytes) grow on branches of mango tree, thereby getting safe shelter but the mango tree remains unaffected. Sucker fishes fix on the body of sharks and get food from discards of shark’s meal, but the shark remains unharmed.

Question 33.
What is symbiosis? Give example.
Answer:
Symbiosis: Symbiosis is an inter-specific cooperation in which two species live in a close physical association and both are benefited in some way or the other. This is also known as obligatory mutualism.
Example: Trichonympha receive shelter and nutrients in the intestine of termites and in return help in the digestion of cellulose of the wood fragments taken by the termites as food.

Rhizobium bacteria trap atmospheric nitrogen and supply it to leguminous plants, and in return they get shelter in the root nodules of those plants.

Question 34.
What is meant by mutualism? Give example.
Answer:
Mutualism: Mutualism is a positive-positive inter-specific interaction, where both members are benefited by one another, but close physical association is not evident.
Example: Insects collect nectar and pollens from flowers. In exchange, they help in spreading pollen grains from one flower to another, thereby helping in reproduction.

Question 35.
What is meant by protocooperation? Give example.
Answer:
Protocooperation: Protocooperation is a positive-positive inter-specific interaction, where both members are benefited but obligatory interdependence is not evident.
Example: Sea-anemone often rides on the shell of hermit crab. Here, sea-anemone intakes discarded food of hermit crab and in return protects it from predators by its stinging cells. This relation is not obligatory because both can survive independently.

Question 36.
How do different organisms remain organised in nature?
Answer:
In nature, all living organisms maintain a close interrelation among themselves and with the non-living components of the environment. This interrelationship helps to organize all the biotic components of nature.

Question 37.
How many types of ecosystem are there?
Ecosystem is normally of two types-
Natural ecosystem: The ecosystem that develops naturally in an environment. Example-Pond ecosystem.
Artificial ecosystem: The ecosystem which is artificially created by human beings. ExampleEcosystem in a crop field.

Question 38.
What is biome? What is biomass?
Answer:
Biome: Biome refers to a living community
characterized by distinctive plant and animal species and maintained under the climatic conditions of the largest geographical region.
Biomass: Biomass refers to the mass of various living organisms in a particular area or ecosystem, at a given time.

Question 39.
What is an ecological niche? What do you mean by planktons?
Answer:
Ecological niche: Ecological niche is defined as the role and the position of a particular species in its environment.
Planktons: Planktons are a diverse group of microscopic organisms which can float freely with the oceanic currents and in other water bodies. There are two types of planktonsphytoplanktons and zooplanktons.

Question 40.
What are phytoplanktons and zooplanktons?
Answer:
Phytoplanktons: The photosynthesising microscopic organisms drifting on the upper surface of water bodies, are known as phytoplanktons. Example- Diatoms, Cyanobacteria, Dinoflagellates etc.

Zooplanktons: The heterotrophic, microscopic organisms belonging to the animal community, that drift on the surface of water body, are called zooplanktons. Example-Jellyfish, Cyclops, Daphnia etc.

Question 41.
Who are called producers of an ecosystem? What are their functions?
Answer:
Producers: In an ecosystem, those organisms, which are capable of synthesizing their own food, are called producers. Green plants (autotrophs) play the role of producer in an ecosystem.

Function: Producers utilize the solar energy to synthesize their own food. They trap the energy from the sunlight and convert it into chemical energy within their body. The food, so produced, are utilized by other members of the ecosystem.

Question 42.
Who are called consumers of an ecosystem? Discuss their types.
Answer:
Consumers: In an ecosystem, the living organisms, who cannot prepare their own food and depend upon plants or other animals for their nutrition, are called consumers. Animals and human beings (heterotrophs) play the role of consumer in an ecosystem.

Types: Depending upon their food habits, consumers may be of various types-

1. Primary consumers: Directly depend on plants (producers) for food.
2. Secondary consumers: Feed on primary consumers.
3. Tertiary consumers: Feed on secondary consumers.

Question 43.
Who are the decomposers in an ecosystem? What is their role in ecosystem?
Answer:
Decomposers: In an ecosystem, the organisms which degrade the complex organic substances of dead bodies of producers and consumers and their organic wastes into simpler substances and obtain food from them are known as decomposers. Microorganisms, such as bacteria, fungus etc. play the role of decomposers in an ecosystem.

Role:

1. They help in decomposition of dead plant and animal remains and organic wastes, thereby preventing environmental pollution.
2. They convert large and complex organic matters into small and simple organic matters. As a result, continuous supply of organic elements on earth is maintained.

Question 44.
Who are the transformers of an ecosystem?
Answer:
The microorganisms, which break simple organic compounds and release inorganic elements from them, are known as transformers. Different denitrifying bacteria, sulphur bacteria, phosphobacteria belong to this group.

Question 45.
What is meant by flora and fauna?
Answer:
Flora: In an ecosystem, the entire plant community of a particular region is referred to as flora.
Fauna: In an ecosystem, the entire animal community of a particular region is referred to as fauna.

Question 46.
What is meant by nutrient cycle? What is its significance?
Answer:
Nutrient cycle: The cyclic process by which organic and inorganic matters of the environment are utilized by the living organisms and are again returned to the environment, thereby maintaining their balance, is known as nutrient cycle.

Significance:

• The constancy of nutrient elements within the environment is maintained.
• In this cycle, producers collect nutrients from the environment and these are returned by decomposers and transformers.

Question 47.
Nutrient cycle is a type of bio-geo-chemical cycle. Explain.
Answer:

• Different living organisms (plants, animals, microbes) participate in nutrient cycle. Therefore, it is a bio-cycle.
• Soil, rock, water etc. are various geographic elements that are included within nutrient cycle. Hence, it is a geo-cycle.
• The nutrient elements participate in various chemical reactions occurring within the body of the living organisms. Hence, it is a chemical cycle.
• Combining the above three conditions, it can be rightly said that the nutrient cycle is a type of bio-geo-chemical cycle.

Question 48.
What is energy flow in an ecosystem? Why it is unidirectional?
Answer:
Energy flow: In an ecosystem, the flow of energy along a food chain, starting from producer and gradually reaching the top level consumer through different trophic levels, is known as energy flow in an ecosystem.

Unidirectional flow: In any ecosystem, energy flow occurs through different trophic levels, starting from producer to consumer to decomposer. But this energy never comes back to the producer again. Due to this reason, energy flow in an ecosystem is unidirectional.

Question 49.
What is meant by trophic level? What is 10% law of energy flow?
Answer:
Trophic level: Trophic level refers to the position of a particular species in the ecological food chain. The organisms are classified on the basis of their feeding habits into four types –

• Producer
• Primary consumer
• Secon-dary consumer
• Tertiary consumer.

10 % law of energy flow: According to this law, each and every trophic level of a food chain in an ecosystem receives 10 % energy from its previous trophic level. This law was proposed by Lindeman.

Question 50.
What is food pyramid? What is energy pyramid?
Answer:
Food pyramid: Food pyramid is the graphical representation of different trophic levels in a food chain, starting from producer at the base, to the top level consumer at the peak.

Energy pyramid: Energy pyramid is the graphical representation of different trophic levels in a food chain, based on the total content of energy trapped in different levels from producer at the base to the consumers at the peak.

Question 51.
What is food chain? What is food web?
Answer:
Food chain: Food chain is a feeding hierarchy of different organisms in an ecological community in which organisms are linked to each other through the transfer of energy via food,

starting from producers or detritus and finishing at the top most level of consumers.

Food web: Food web is the network of several food chains, interconnected at different trophic levels, so as to develop a distribution system of energy via food amongst every member of the biotic community.

Question 52.
What is adaptation? Write two features of food chain.
Answer:
Adaptation: Adaptation is an evolutionary process by which an organism undergoes permanent anatomical or physiological or behavioral changes, in order to cope with the changing environment.

Features of food chain:

1. Energy flow occurs according to the sequential arrangement of various trophic levels in a food chain, i.e., producer arrow primary consumer arrow secondary consumer arrow tertiary consumer.

2. Different food chains in an ecosystem connect together to form a food web.

Question 53.
What is a grazing food chain?
Answer:
The food chian that starts from producers and proceeds through different consumers from lower to higher level, is known as grazing food chain.

Question 54.
What is parasitic food chain?
Answer:
The food chain that starts from producers (such as plants) and ends to any parasite, is called parasitic food chain.

Question 55.
What is detritus food chain?
Answer:
The food chain that starts from dead and decaying organic matters and ends to any large consumer, is called detritus food chain.

Question 56.
What is diurnal thermoperiodicity?
Answer:
Diurnal thermoperiodicity is response of organisms to daily changes of temperature. Example-Day time temperature is favourable for photosynthesis, transpiration, etc. and low temperature at night is suitable for storage of food, growth etc. Seed germination is influenced by diurnal changes of temperature.

Question 57.
What is seasonal thermodynamicity?
Answer:
Seasonal thermodynamicity is response of organisms to seasonal changes in temperature along with photoperiodicity. It controls flowering, fruiting, leaf fall, growing of new leaf etc. Example-Apple tree needs exposure to 7° C for more than 800 hours to set fruit. Wheat needs 10-25° C temperature in early winter for seed germination.

Question 58.
What do you mean by vital index?
Answer:
The percentage ratio of natality over mortality within a population in a given time, is known as vital Index. Vital index determines the normal growth of a population.

Vital Index (VI ) = \(\frac{\text { Natality }}{\text { Morality }}\) × 100

In case of growing population, V is >100
In case of negative growth, quad V is <100
In case of zero growth or stable population,
V is = 100.

Question 59.
Distinguish between producers and consumers.
Answer:

Features	Producers	Consumers
1. Source of food	Synthesise own food by photosynthesis	Depend directly or indirectly on producers for food
2. Ecological status	Belong to the first trophic level	Belong to any of the second to the top most trophic levels
3. Source of energy	Get energy directly from the sun	Get energy from the previous trophic level
4. Example	All green and other photosynthetic plants and microorganisms	All animais and nonchlorophyllous plants

Question 60.
Distinguish between producers and decomposers.
Answer:

Features	Producers	Decomposet
1. Source of food	Synthesise own food by photosynthesis	Draw nutrients from dead and decaying matters
2. Type of nutrition	Perform autotrophic nutrition	Perform saprophytic nutrition
3. Role in ecosystem	Synthesise complex organic compound (food matter) from simple inorganic matters	Break complex organic matters as free elements
4. Example	All green and other photosynthetic plants and microorganisms	Microbes, including decomposing bacteria and fungi

Question 61.
Distinguish between consumers and decomposers.
Answer:

Features	Consumers	Decomposers
1. Type of food	Complex organic matters from live organisms	Dead and decaying matters
2. Type of nutrition	Perform heterotrophic nutrition	Perform saprophytic nutrition
3. Role in ecosystem	Collect energy from producers and other consumers	Break complex organic matters as free elements
4. Example	All animals and non-chlorophyllous plants	Microbes, including decomposing bacteria and fungi

Question 62.
Distinguish between macro-consumers and micro-consumers.
Answer:

Features	Macro-consumer	Micro-consumer
1. Size	Larger and multicellular	Smaller and mostly unicellular
2. Type of nutrition	Autotrophic or heterotrophic	Saprophytic
3. Source of energy	Get energy indirectly from producers or other consumers	Get energy by breaking organic matters
4. Exampie	All animals and plants	Microbes, including decomposing bacteria and fungi

Question 63.
Distinguish between mutualism and commensalism.
Answer:

Features	Mutualism	Commensalism
1. Nature	Both the associates are benefited	One of the associates is neither benefited nor harmed
2. Contact	Close contact is maintained between two associates	Close contact between the associates is not mandatory
3. Example	Reiation between pollinating insects and flowers	Relation between epiphytic orchids and mango tree

Question 64.
Distinguish between intra-specific competition and inter-specific competition.
Answer:

Features	Intra-spesific competition	Inter-specific competition
1. Nature	Competition between members of the same species	Competition between members of different species
2. Causes of competition	To acquire food, shelter and sex partner	To acquire food and shelter
3. Predation	Predation rarely occurs	Predation is very common

Question 65.
Distinguish between food chain and food web.
Answer:

Features	food chain	Food web
1. Involvement	One species is involved in each trophic level	Many species are involved in each trophic level
2. Prey-predator relation	Specific	Diverse
3. Energy flow	Energy flows in a straight linear path	Energy flows in a complex reticular path

Question 66.
Distinguish between grazing food chain and detritus food chain.
Answer:

Features	Grazing food chain	Detritus food chain
1. Source of energy	Sun	Organic matters from dead and decaying substances
2. Flow of energy	Starts from producers and reaches the top most level of consumers via lower levels of consumers	Starts from detritus and reaches the top most level of consumers via detritivores and other lower consumers

Question 67.
Distinguish between population and community.
Answer:

Features	Population	Community
1. Definition	Maintain interbreeding relation	Maintain prey-predator or hostparasite or symbiotic relations
2. Relation type	Belong to a smaller level of ecological study	Belong to a larger level of ecological study
3. Span	Members are not interconnected in food chain or food web	Members are interconnected in food chain or food web
4. Interaction	Sum total of the members of a single species inhabiting in a specific region in a specific time	Sum total of the members of different interacting populations inhabiting in a specific region in a specific time

Question 68.
Distinguish between population and community.
Answer:

Features	Natality	Mortality
1. Nature	Indicates the rate of increase of a population due to birth	Indicates the rate of decrease of a population due to death
2. Effect on biomass	Biomass is directly proportional to natality	Biomass is inversely proportional to mortality
3. Effect on population	Population size increases due to natality	Population size decreases due to mortality

Long Questions and Answers : (5 marks for each question)

Question 1.
Briefly explain the impact of light on living organisms.
Answer:
Effect of light on living organisms :

1. In green plants, chloroplasts tend to concentrate on that surface of a leaf which gets more light.

2. In some plants, span of day light effects their flowering and other physiological activities. This phenomenon is known as photoperiodism. The plants, such as dahlia, sugarcane, strawberry etc., flowers bloom during shorter day light period and are called Short Day Plants (SDP). The plants, such as pea, radish, spinach etc., flowers bloom during longer day light period and are called Long Day Plants (LDP). In some plants, such as tomato, cucumber, cotton etc., span of day light does not have any significant impact on blooming. These are known as Day Neutral Plants (DNP).

3. Light enhances the pigmentation of skin. Animals living in hot and humid climate have darker body colour. Animals living in polar region have pale body colour. Similarly, human population living in strongly sunlit regions have darker body colour.

4. Photoperiod is the controlling factor for breeding features of different animals. The animals, such as sheep, goat, deer etc. breed during decreasing day length of autumn, known as Short Day Breeders (SDB). On the other hand, lemurs, horses, hamsters etc. breed during increasing day length of spring and are known as Long Day Breeders (LDB). Also, there are certain animals, whose breeding is not affected by day length. These animals, include guinea pig, cat, rabbit etc.

Question 2
Explain the effect of temperature on living world.
Answer:
Effect of temperature on living organisms

1. Plants growing in desert region have light-coloured body hairs, acting as heat reflectors. Their leaves are modified into spines and they have less stomata to reduce transpiration. The overall surface area of these plants are less, compared to other plants. As a result, area exposed to air is reduced, thereby reducing the rate of transpiration.

2. Plants growing in hot but humid climate of tropical region, have broad flat and thick green leaves to increase the rate of transpiration.

3. In amphibians, reptiles and fishes, body temperature varies with environmental temperature. These animals are therefore, known as poikilothermic animals. On the other hand, birds and mammals maintain constant body temperature in any environment. These are known as homeothermic animals.

4. Some animals, such as toads, house lizards, ants etc., can withstand wide range of temperature variation in the environment. These are called eurythermal animals. Some animals, such as fishes and cnidarians cannot tolerate wide temperature fluctuation. These are called stenothermal animals.

Question 3.
Explain the effect of relative humidity on living organisms.
Answer:
Effect of relative humidity on living organisms

1. Plants growing in arid climate develop features that help them to resist atmospheric dryness. They have elaborate root system, few leaves, less stomata, waxy leaf and stem surfaces, elaborate tap root system etc. to conserve and collect more water.

2. Plants growing in moist environment have wider leaves with many stomata to dispose excess water and these plants perform transpiration at higher rate. Certain plants like tomato, a few grasses dispose excess water as tiny droplets through special water pore, called hydathodes, situated along the edge of the leaves to get rid of excess water.

3. Animals living in desert regions have few sweat glands, discharge scanty urine and dry faeces. A desert reptile, Moloch horridus have uniquely designed spiny skin to reduce water loss and maintain body humidity. Insects living in desert region bear a layer of waxy cuticle over their body to reduce water loss.

4. Excessive relative humidity is favourable for the growth of fungal population. In moist weather, different pathogenic and non-pathogenic fungi grow. In moist weather, population of bryophytes and pteridophytes also increase significantly.

Question 4.
Explain the role of different factors regulating population size.
Answer:
Factors regulating population size
Four factors play significant role in regulating the population size. These are-

• natality
• mortality
• immigration
• emigration.

1. Natality: Natality can be defined as the ratio of total live births to a population in a specified community or area, over a specific period of time. We may express natality or birth rate as the number of live births per 1000 of the population per year. It can be represented as the following equation-

B = \(\frac{n d}{\mathrm{~N}}\) × 1000, text where,
B = natality or birth rate,
N = total number of individuals in a population,
nb = number of live births.

2. Mortality: Mortality can be defined as the ratio of total deaths to a population in a specified community or area, over a specific period of time. Population size decreases with the increase in mortality of the individuals.
Death rate or mortality is often expressed as the number of deaths per 1000 of the population per year. It can be represented as the following equation.

D = \(\frac{n d}{\mathrm{~N}}\) × 1000, where, D =text mortality or death rate,
N = total number of individuals in a population,
nd = number of deaths

3. Immigration: Immigration is the mass entry of individuals in a population in a given area, from some other place. Therefore, immigration increases the population size very quickly.

4. Emigration: Emigration, on the other hand, means the mass departure of individuals from a population in a given area, to some other place. By emigration, population size goes down abruptly.

5. iscuss different levels of positive inter-specific interactions in the living world.
Positive inter-specific interactions in living world Positive interactions in living world are collectively known as cooperation. In nature, several species live together with cooperation. Here, both or at least one of the species, involved in the relation is benefited, but neither of them is harmed. This cooperative relationship between different species help in better growth, reproduction and survival. Cooperation may be of different types-

• symbiosis
• mutualism
• protocooperation
• commensalism.

These are described below.
1. Symbiosis: Symbiosis is an inter-specific cooperation, in which two species live in a close physical association and both are benefited some way or the other. Symbiosis may be obligate (both the species entirely depend upon one another for survival) or facultative (both the species do not depend on their partner for survival).

Example-In lichens, algae and fungi develop symbiotic association. Here, the fungus acts as a settling platform and provides water and mineral to the alga. In return, the alga synthesises food for both.

2. Mutualism: Mutualism is the cooperation between two species, in which both are benefited but close physical association and nutritional interdependence between them is not evident.

Example-Insects collect nectar and pollen from flowers. In exchange, they help in spreading pollen grains from one place to another that help in plant reproduction.

3. Protocooperation: Protocooperation is a positive inter-specific interaction, where both members are benefited but, they do not depend on one another for survival. Growth and survival of both the species is possible even in the absence of this interaction.

Example-Sea-anemone often rides on the shell of hermit crab. Here sea-anemone intakes discarded food of the hermit crab and in return protects it from the predators by its stinging cells. This relation is not obligatory because both can live independently.

4. Commensalism: Commensalism is the cooperation between two species, where one of the members is benefited, but the other member is neither benefited nor harmed. In this relation, close association occurs between the two species, but nutritional interdependence is not developed.

Example-Epiphytic orchids grow on the branches of big trees, but carry out photosynthesis independently. By this process, orchids escape predation, but the host tree is neither harmed nor benefited.

Question 6.
Discuss about competition, predation and parasitism in the living world.
Answer:
Interactions in living world :
In living world, introspecific and inter-specific interactions involve two individuals, of which either both or one of the members is benefited and the other member sustains loss, get injured or die. Among these interactions competition, predation and parasitism are important. These are described below-
1. Competition: Competition can be defined as a negative interaction, where members of the same or other species fight with each other to acquire limited supply of environmental resources food, water, shelter and mates. Competition is mainly of two types-[A] intra-specific competition and [B] inter-specific competition.
Intra-specific competition: in this competition, members of the same species fight among themselves for food and mate.

Example-Fighting among dogs or fighting among cats.

Inter-specific competition: This competition takes place between members of two or more different species, for food and shelter.
Example-Sparrows quarrelling with common maina or dogs fighting with cats.

2. Predation: Predation is another type of inter-specific interaction, in which one species attacks another species to kill and consume it. Here, the attacker is known as predator and the one, which is attacked, is called the prey. The predator obtains nutrition and energy from the prey.
Example-Tigers kill deer, praying mantis kills other insects, pitcher plants trap insects etc. In all the above examples, the former ones are the predators and the latter ones are the prey,

3. Parasitism: Parasitism is the most advanced type of inter-specific interaction, in which one species depends upon other species for food or shelter or both. Here, the dependent member (parasite) is benefited, but the other member (host) is deprived.
Example-Tapeworms (Taenia), roundworms (Ascaris) etc. are the parasitic worms that draw nutrients from human (host). Dodder plants (Cuscuta sp.) suck nutrients from phloem of the host plants.

Question 7.
Write down a brief note on different types of parasites in living world.
Answer:
Different types of parasites
From evolutionary point of view, parasitism is the most advanced type of inter-specific interaction, in which one species depends upon other species for food or shelter or both. Here, the dependent member (parasite) is benefited, but the other member (host) is deprived. Different types of parasites are described below.

Based on their position in host body, parasites are classified into two types-
1. Ectoparasites: These parasites draw nutrients from outside the body of the host.
Example-Louse, ticks, bedbugs live on body surface of mammals, In case of parasitism in plants, Dodder plant needs a special mention. Dodder plant (Cuscuta sp.) produces root like structures, called haustoria, which penetrate the vascular bundle of the host and derive nutrition directly.

2. Endoparasites: These parasites live inside the body of the host and collect nutrients from them.
Example-Tapeworm, roundworm, Plasmodium (maiarial parasite), liver fluke etc. live inside human body.

On the basis of the dependance of parasitism, they may be of two types-

Obligatory parasites: These species completely depends upon a host to complete their life cycle. Example-Tapeworm, roundworm, Plasmodium etc. spend their life permanentiy as parasites.

Facultative parasites: These species can survive without the parasitic mode of life but can also adapt a parasitic life.
Example-The parasitic nematode Strongyloides stercoralis can also be free living.

Question 8.
Briefly describe the general structural aspects of an ecosystem.
Answer:
Structural aspect of ecosystem :
An ecosystem constitutes two types of components or factors – [1] abiotic factors and [2] biotic factors.
1. Abiotic factors: Abiotic factors include the non-living components of ecosystem. They have direct impact on life process of living organisms. Various abiotic component of the ecosystem areorganic component, inorganic component and physical component.

Organic component: Different organic matters, such as carbohydrate, protein, fat etc. are obtained from the dead and decaying organic remains of plants and animals. These organic matter mix with the soil and produce humus, which play a significant role in regulating soil fertility.

Inorganic component: It includes various mineral elements (such as calcium, magnesium, salts of sodium, potassium, sulphur etc.) and gases (such as oxygen, nitrogen, carbon dioxide etc.). Green plants use these elements for synthesizing their own food.

Physical component: The physical component of ecosystem includes various factors, such as light, temperature, humidity, altitude, steepness of slope, firmness of soil. Of these, the most important physical factor is light, more specifically sunlight. Green plants trap the solar energy and convert it to chemical energy to prepare their own food by the process of photosynthesis.

2. Biotic factors: The living organisms constitute the biotic factors of an ecosystem. Various components of biotic factors are- autotrophs and heterotrophs.
Autotrophs: All those organisms, capable of synthesizing their own food by photosynthesis or chemosynthesis, are known as autotrophs. All green plants, photosynthetic and chemosynthetic microorganisms are the examples of autotrophs.

Heterotrophs: The living organisms, which depend directly or indirectly on autotrophs for their nutrition are known as heterotrophs. Heterotrophs may be classified into three typesconsumers, decomposers and transformers.

1. Consumers: These organisms directly or indirectly consume autotrophs, especially green plants and plant products, to gain nutrition and energy. So, they are called consumers. Depending upon the nature of food they eat, consumers are classified into three types-

• Primary consumers: These animals directly consume green plants or plant products for nutrient and energy. Example-Deer, cow, grasshopper etc. (all herbivores).
• Secondary consumers: These animals directly consume herbivores for nutrition. Example-Frogs, small birds, rat, lizards etc.
• Tertiary consumers: These are larger consumers, which feed on both primary and secondary consumers. Example-Owl, tiger, lion, falcon, king cobra etc.

2. Decomposers and transformers: The organisms, which get their nutrients from dead organisms and decaying organic matter and in this process break the larger organic compounds into smaller molecules, are called decomposers. Different microorganisms (such as bacteria) and some fungi (such as Agaricus) belong to this group. Some bacteria act upon those small organic molecules, that are the end products of decomposition. These bacteria completely break those organic molecules and return the elementary components in nature. They are called transformers.

Question 9.
How does energy flow through an ecosystem?
Answer:
Energy flow in ecosystem :

Energy flow can be defined as the unidirectional transfer of solar energy, in the form of organic matters, from producers to the highest level of consumers, through different trophic levels via food chains. Sun is the ultimate source of energy in all ecosystems. Only photosynthetic organisms are capable of trapping and transforming the light energy form the sun into chemical energy in the form of food. This energy is transferred from producers to consumers through food chain, which is called flow of energy. Energy flow in an ecosystem occurs through the following three steps.

1. Acquiring energy: All green plants and other photosynthetic microorganisms can trap radiant energy from the sun. Only 0.02 % of the total energy of sun comes to the earth as light. Of this, only 0.1 % is trapped by means of photosynthesis. This process is called acquiring energy.

2. Utilizing energy: The light energy from the sun, trapped by the green plants, is oxidized during respiration to produce chemical energy. This energy is necessary to carry out different metabolic activities. This process is called utilization of energy.

3. Iransfer of energy: From the green plants, net primary production passes to different level of consumers through food chain. The herbivores or primary consumers directly get their share of energy from producers. By respiration, primary consumers utilize a greater portion of the transferred energy. the remaining portion of energy is then transferred to the higher level of consumers in the same way.

When energy flow occurs from one trophic level to another, subsequently an amount of energy is lost in the process which cannot be regained further. Moreover, the energy that follows from producer to consumer, can never be returned to the producer. Hence, the flow of energy is always unidirectional.

According to famous scientist, Lindeman, out of the total energy produced or received in a particular trophic level, only 10 % of it is transferred to the next trophic level. This is known as Lindeman 10 % law. As a result, very less amount of energy is received by the members of highest trophic level.

Question 10.
With an example, describe how biogeochemical cycle of a nutrient operates in nature.
Answer:
Biogeochemical cycle of a nutrient
Living organisms obtain different nutrients (such as C, H₂, O₂, N₂, S, P, Ca etc.) from the environment through food and as respiratory gases. These elements act as structural components of a living body. These elements
are the returned to the environment by excretion, respiration and decomposition of dead or decaying organic matters. Within biosphere, several structurally and metabolically important elements are exchanged between the biotic and the abiotic components of the ecosystem. This exchange of elements occurs through a cyclic path, known as nutrient cycle or biogeochemical cycle.
Here, the carbon cycle is discussed below as an example.

Carbon cycle refers to the cyclic exchange of carbon in the physical and biological systems.

• Reservoir Pool: Carbon bed of lithosphere act as reservoir pool for carbon.
• Cyclical Pool: The cyclic pool of carbon involves the atmosphere and the sea water.

3. Utilisation of carbon from nature: It involves two pathways-

Biological path: The biological path of carbon utilization involves activities of green plants and shelled molluscs. Green plants trap carbon within cellular compounds by photosynthesis. Shelled molluscs utilize carbon of CO₂ to prepare their shell. The echinoderms use CO₂ from air to form the spinous body surface with ossicles, which is made up of calcium carbonate.

Physiochemical path: The physiochemical path of carbon utilization involves certain marine deposits, such as limestone, dolomite, feldspar etc. absorb carbon (CO₂) to prepare calcium carbonate (CaCO₃).

4. Return of carbon to nature: Carbon is returned to the environment by two pathways-

Biological path: All living forms (except a few anaerobes) release CO₂ by respiration. CO₂ is released into the nature by decomposition of organic matters. After the death of molluscs and sea corals, their calcium carbonate rich shells are decomposed to produce CO₂.

Physiochemical path: Combustion of fossil fuel, wood etc., forest fire and volcanic eruption produce huge quantity of CO₂. This cyclic process of utilization and return of carbon to nature occurs at same rate. This helps to maintain constant carbon content in the environment.

Detailed explanations in West Bengal Board Class 9 Life Science Book Solutions Chapter 2.1 Classification of Kingdom Animalia offer valuable context and analysis.

WBBSE Class 9 Science Chapter 2.1 Question Answer – Biomolecules and their Behaviour

Very Short Questions and Answers : (1 mark for each question)

Question 1.
What are we made up of?
Answer:
We are made up of millions of inorganic and organic molecules.

Question 2.
How do we denote the large molecules of the body of an organism?
Answer:
We denote the large molecules of the body of an organism as macromolecules.

Question 3.
How do we denote the elements, which we need in a very little quantity?
Answer:
The elements that are required in very little quantity in the body of an organism are denoted as micromolecules.

Question 4.
Which simple compound does a living cell need the most, for survival?
Answer:
Water is a simple compound, which a living cell needs the most, for its survival.

Question 5.
What are biomolecules?
Answer:
Biomolecules are the organic molecules produced or involved in various biochemical reactions within the cells or inside the body.

Question 6.
Which inorganic acid plays a very important role in our digestion process?
Answer:
Hydrochloric acid is the inorganic acid, which plays an important role in our digestion process.

Question 7.
What does carbonic acid do in our body?
Answer:
Carbonic acid is involved in the transportation of CO₂, out of the body, via respiratory exchange of gases.

Question 8.
Which gas is involved in energy generation in a living body?
Answer:
Oxygen is involved in the energy generation in a living body.

Question 9.
Which anabolic process needs CO₂?
Answer:
Photosynthesis is the anabolic process, which needs CO₂.

Question 10.
Which is the most abundant salt in our body?
Answer:
Sodium chloride (NaCl) is the most abundant salt in our body.

Question 11.
Which two elements are essential for our skeletal system?
Answer:
Calcium and phosphorus are the two elements essential for our skeletal system.

Question 12.
What is the similarity among monosaccharides, amino acids and fatty acids?
Answer:
Monosaccharides, amino acids and fatty acids are all organic micromolecules.

Question 13.
What is the basic difference between nucleotides and a nucleic acid?
Answer:
Nucleotides are organic micromolecules and nucleic acid is an organic macromolecule.

Question 14.
Which type of sugars cannot be hydrolysed into smaller carbohydrates?
Answer:
Monnsaccharfths cannot be hydrolysed into smaller carbohydrates.

Question 15.
Which type of sugar is called a disaccharide?
Answer:
The sugar having two monosaccharide units is called a disaccharide.

Question 16.
How do you denote tite sugars composed of 3 to 9 monosaccharide units?
Answer:
The sugars with 3 to 9 monosaccharide units are denoted as oligosaccharides.

Question 17.
Which type of sugars is generally insoluble in water and tasteless in nature?
Answer:
Polysaccharides are generally insoluble in water and tasteless in nature.

Question 18.
What is calorltic value?
Answer:
blat heat energy liberated by the complete oxidation of Unit mass of a matter is known as its calorific value.

Question 19.
How much heat energy is liberated from one gram of glucose on its complete oxidation?
Answer:
On complete oxidation of one gram of glucose molecule, 4A kcal heat energy is liberated.

Question 20.
What is the full form of MUFA?
Answer:
The full form of MUFA is Mono Unsaturilted Fatty Acid.

Question 21.
Which type of biomolecule is commonly consumed by organisms for energy generation?
Answer:
Living organisms commonly consume carbohydrates for energy generation.

Question 22.
Which type of biomolecule is commonly consumed by organisms as body building materials?
Answer:
Living organisms commonly consume proteins as body building materials.

Question 23.
Which type of biomolecule do living organisms commonly store within the body?
Answer:
Living organisms commonly store fat within the body.

Question 24.
Which type of material in food helps in faeces formation and facilitate defecation?
Answer:
A polysaccharide, called cellulose, helps in face formation and facilitates defecation.

Question 25.
Which type of food should a growing baby be fad with?
Answer:
A Growing baby should be fed with protein-rich food for maximum muscular growth.

Question 26.
How are the two strands of a DNA molecule zipped together?
Answer:
The two strands of a DNA molecule are zipped together by weak hydrogen bonds between the bases.

Question 27.
Name the bond by which nucleosides of a nucleic acid strand remain attached one after another.
Answer:
The nucleosides of a nucleic acid strand remain attached one after another by phosphate bonds.

Question 28.
Which nucleic acid is mainly involved in carrying hereditary features from parents to oftsprings?
Answer:
Mainly DNA is involved in carrying hereditary features from parents to offsprings.

Question 29.
Which type of organisms synthesise most of the vitamins?
Answer:
Green plants synthesise most of the vitamins.

Question 30.
Which vitamin is synthesised within our skin on exposure to sun?
Answer:
Vitamin D is synthesised within our skin on exposure to sun.

Question 31.
Which type of vitamin should a person take in for problems with vision after sunset?
Answer:
A person having problems with vision after sunset should take vitamin A.

Question 32.
Give an example of an aldose sugar.
Answer:
Glucose is an example of aldose sugar.

Question 33.
Which two elements are essential for neural transport?
Answer:
Sodium and potassium are necessary for neural transport.

Question 34.
Which two simplest molecular units form a lipid molecule?
Answer:
Fatty acid and glycerol are the two simplest molecular units, which form a lipid molecule.

Question 35.
Name a reducing sugar.
Answer:
Glucose is a reducing sugar.

Question 36.
Name a non-reducing sugar.
Answer:
Sucrose is a non-reducing sugar.

Question 37.
Name two fat soluble vitamins present in egg.
Answer:
Vitamin A and vitamin D are two fat soluble vitamins present in egg.

Question 38.
Which mineral is essential for haemoglobin formation?
Answer:
Iron is essential for haemoglobin formation.

Question 39.
Which element is involved in the formation of thyroxin hormone?
Answer:
Iodine is involved in the formation of thyroxine hormone.

Question 40.
Name a mineral essential for muscle contraction and blood coagulation.
Answer:
Calcium is essential for muscle contraction and blood coagulation.

Question 41.
What is the ratio of hydrogen and oxygen in carbohydrates?
Answer:
In carbohydrates, hydrogen and oxygen are present in the ratio of 2: 1.

Question 42.
Give an example of a ketohexose.
Answer:
Fructose is an example of a ketohexose.

Question 43.
Name a basic protein.
Answer:
Histone is a basic protein.

Question 44.
What is the chemical name of vitamin P?
Answer:
Chemical name of vitamin P is citrine.

Question 45.
Name an iron-containing enzyme.
Answer:
Catalase is an iron-containing enzyme.

Question 46.
Name two triose sugars.
Answer:
Two triose sugars are monotriose and dihydroxyacetone.

Question 47.
Name the sweetest carbohydrate.
Answer:
The sweetest carbohydrate is fructose or fruit-sugar.

Question 48.
In animal body, fat is stored in which tissue?
Answer:
In animal body, fat is stored in adipose tissue.

Question 49.
Which disease is caused in children due to deficiency of iodine?
Answer:
Cretinism is caused in children, due to deficiency of iodine.

Question 50.
Name two vitamins present in lemon.
Answer:
Vitamin C (ascorbic acid) and vitamin P (citrine) are two vitamins present in lemon.

Question 51.
What is the chemical name of vitamin D?
Answer:
Chemical name of vitamin D is calciferol.

Question 52.
Deficiency of which vitamin results in teeth and gum deformity?
Answer:
Deficiency of vitamin C results in deformity of teeth and gums.

Question 53.
What is the minimum number of monosaccharides required to form a polysaccharide?
Answer:
At least 10 monosaccharide molecules are necessary to constitute a polysaccharide.

Question 54.
What is the main function of vitamin A in human?
Answer:
Vitamin A helps in the production of rhodopsin pigment in rod cells of human eye.

Question 55.
What is meant by a polypeptide?
Answer:
Large polymers of numerous amino acid molecules, linked together by peptide bonds, are known as polypeptides.

Short Questions and Answers : (2 marks for each question)

Question 1.
Schematically represent the molecules of life.
Answer:
Molecules of life are mentioned in the following chart-

Question 2.
Why are different molecules so important for our existence?
Answer:
Life has originated from different non-living molecules through complex chemical reactions. These molecules build our body as well as help to maintain all our life processes. That is why, these are important for our existence.

Question 3.
Mention the roles of two biologically important gases, which organisms absorb directly from atmosphere.
Answer:
Oxygen and carbon dioxide are the two biologically important gases, which organisms absorb directly from atmosphere. All aerobic organisms utilise oxygen to oxidise glucose and liberate energy, necessary to run their life processes. All autotrophs use carbon dioxide as the raw material for photosynthesis to prepare their food.

Question 4.
Mention the roles of an acid and a base in human body.
Answer:
Hydrochloric acid, secreted in stomach, converts pepsinogen into active pepsin to start digestion of protein, HCl also helps to hydrolyse sucrose. Sodium bicarbonate, present in bile, is basic in nature, which neutralises the acidic contents of stomach as soon as it reaches the duodenum.

Question 5.
Classify biomolecules based on their molecular weight and give two examples for each.
Answer:
On the basis of molecular weight, organic molecules or biomolecules can be differentiated into two basic types. These are – bio-micromolecules and bio-macromolecules. Examples of bio-micromolecules are mono-saccharides, amino acids etc. Examples of bio-macromolecules are proteins, nucleic acids etc.

Question 6.
What is meant by carbohydrates? Give two examples.
Answer:
Carbohydrates are the organic compounds made up of carbon, hydrogen and oxygen, in which hydrogen and oxygen maintain a ratio of 2:1. Examples — Glucose and cellulose.

Question 7.
Why are carbohydrates called saccharides? Give any two examples of two different types of saccharides.
Answer:
Naturally occurring carbohydrates or the end products of their hydrolysis are sweet to taste. In Greek, ‘saccharides’ means sugars, therefore, carbohydrates are commonly called saccharides. Saccharides are of different types – mono, oligo and polysaccharides. Two example of monosaccharides are glucose and fructose and two examples of oligosaccharides are sucrose and raffinose.

Question 8.
Mention plant and animal carbohydrates.
Answer:
Carbohydrates are mostly found in different plant products – rice, wheat, maize, potato, beet, arum are the sources of starch. Various fruits like mango, banana, oranges etc. provide fructose. Juice of date-palm plant, sugarcane are rich in sucrose and glucose. All green vegetables and some fruits, like wood apple, water melon etc. are good sources of cellulose. Milk is an animal product that contains milk sugar (lactose).

Question 9.
what is meant by sugars? Give example of two biologically important sugars.
Answer:
Carbohydrates with low molecular weight, high water solubility and sweet taste are called sugars.
Example -Two biologically important sugars are glucose and fructose.

Question 10.
What is glycosidic bond?
Answer:
The bond that develops between two or more monosaccharide units to form disaccharide, oligosaccharide or polysaccharide molecules is known as glycosidic bond.

Question 11.
What is meant by monosaccharides? Mention the basic molecular formula of monosaccharides.
Answer:

• Monosaccharides: Monosaccharides are the simplest form of carbohydrates, which have low molecular weight, high water solubility, sweet taste and cannot be hydrolysed further into smaller carbohydrates. Fructose is one type of monosaccharide.
• Molecular formula: The basic molecular formula of carbohydrate is (CH₂O)_n.

Question 12
What is meant by disaccharides? Give two examples of biologically important disaccharides.
Answer:
Disaccharides are the sweet tasting, watersoluble carbohydrates, composed of two monosaccharide molecules. Examples-Sucrose and lactose are the two biologically important disaccharides.

Question 13.
What are oligosaccharides? Mention the basic molecular formula of oligosaccharides.
Answer:

• Oligosaccharides: Oligosaccharides are the complex type of carbohydrates, which are composed of 3 to 9 monosaccharide units. Example-Raffinose.
• Molecular formula: The basic molecular formula of oligosaccharides is C_n(H₂O)_n-1

Question 14.
What are polysaccharides? Mention the basic molecular formula of polysaccharides.
Answer:
Polysaccharides: Polysaccharides are water insoluble and tasteless type of complex carbohydrates, composed of ten to numerous monosaccharide units. Example-Cellulose.
Molecular formula: The basic molecular formula is (C₆H₁₀O₅)_n

Question 15
Why carbohydrates are called ‘protein sparing food’?
Answer:
By consuming adequate carbohydrates, an organism can survive without taking dietary proteins. Within the body, these carbohydrates are transformed into amino acids by some metabolic processes. These amino acids consequently form different proteins. Therefore, carbohydrates are called ‘protein sparing food.’

Question 16
What is meant by amino acid? Give example.
Answer:
An amino acid is the structural and functional unit of a protein which is composed of carbon, hydrogen, oxygen and nitrogen, typically possessing an amino (-NH₆) group and a carboxyl (-COOH) group.
Example-Glycine, Alanine, Histidine etc.

Question 17.
What is an ester?
Answer:
The organic compound, that is formed by the reaction of an alcohol and an organic acid, is called ester. Example-Glycerides phosphoester.

Question 18.
What are proteins? Give example.
Answer:
Proteins are biologically important macromolecules, composed of either a number of amino acids or a combination of amino acids and few non-amino acid components, acting as the building materials of all living bodies. Example – Albumin, Globulin, Haemoglobin etc.

Question 19.
Mention two characteristic features of proteins.
Answer:
Two characteristic features of proteins are as follows-

• Proteins are polymers of amino acids which are basically composed of carbon, hydrogen, oxygen and nitrogen.
• Proteins are mostly soluble in water and they coagulate on heating.

Question 20.
What is meant by simple proteins? Give example.
Answer:
The proteins, which do not contain anything other than amino acids, joined by peptide bonds, are known as simple proteins. Example – Albumin, Globulin, Glutenin etc.

Question 21.
What is meant by conjugated proteins? Give example.
Answer:
The proteins which are composed of amino acids and some non-amino acid components, are called conjugated proteins. Example – Haemoglobin, Haemocyanin, Cytochrome etc.

Question 22
What is meant by derived proteins?
Answer:
Certain proteins are produced during the hydrolytic breakdown of larger protein molecules. These are called derived proteins. Example – Peptone, Metaprotein, Proteose etc.

Question 23.
What is meant by basic amino acids? Give example.
Answer:
The amino acids which have two or more basic amino groups (-NH₂), are called basic amino acids.
Example – Lysine, Arginine, Histidine etc.

Question 24.
What is meant by acidic amino acids? Give example.
Answer:
The amino acids which have two or more acidic carboxyl groups (-COOH), are called acidic amino acids. Example – Glutamic acid, Aspartic acid etc.

Question 25.
What is meant by essential amino acids? Give example.
Answer:
The acids, which are indispensable for normal growth and development, but are not synthesised within the body and can only be taken in as food, are known as essential amino acids.
Example: Tryptophan, Phenylalanine, Threonine, Valine, Methionine, Leucine, Isoleucine.

Question 26
Mention the sources of proteins.
Answer:
Proteins are available in both animal and plant products. Animal sources of proteins are fish, meat, egg and milk. Among plant sources, pulses, soyabean, gram etc. are rich in proteins. Rice, wheat, certain fruits and vegetables also contain a little bit of protein.

Question 27.
Mention the importance of protein in human body.
Answer:
Protein is the building block of our body. For this reason, the body needs adequate supply of proteins through food. Deficiency of protein may lead to retardation of physical as well as mental growth. Development of brain, eye, bones and muscles will be affected the most. Several physiological activities are also hampered due to protein deficiency.

Question 28.
Mention two diseases caused due to protein malnutrition.
Answer:
Marasmus and Kwashiorkor are two commonly known diseases which are caused due to protein malnutrition.

Question 29.
What is meant by fatty acids? Give example.
Answer:
Fatty acids are the smaller biomolecules, composed of three elements like carbon, hydrogen and oxygen, having a hydrocarbon chain ending with a carboxyl (-COOH}) group and taking part in the formation of lipids. ExampleLanoline, Linolenic acid.

Question 30.
Why egg is called the reference protein?
Answer:
Egg contains almost all proteins in perfect proportions as per requirement of the body. Nutritionists, therefore measure the nutritional value of other proteins with reference to the proteins present in egg, so egg is known as the reference protein.

Question 31.
What is meant by saturated fatty acid?
Answer:
The fatty acids in which carbon atoms are joined to each other by monovalent bonds, are known as saturated fatty acids. ExamplePalmitic acid, Stearic acid etc.

Question 32.
What is meant by unsaturated fatty acid?
Answer:
The fatty acids in which carbon atoms are joined to each other by bivalent or trivalent bonds, are known as unsaturated fatty acids. Example-Linolenic acid, Linoleic acid etc.

Question 33.
What is meant by lipids? Mention the dietary sources of lipids.
Answer:

• Lipids: The esters of fatty acids and alcohols which are insoluble in water but soluble in organic solvents like acetone, benzene, chloroform, ether etc., are known as lipids.
• Sources of lipids: Butter, ghee, oils, coconut, different types of oil seeds, red meat are the common dietary sources of lipids.

Question 34.
What is meant by essential fatty acids?
Answer:
Certain physiologically important fatty acids are never synthesised within the body. We get it from dietary fats. These are called essential fatty acids. Example-Linolenic acid, Linoleic acid are two essential fatty acids.

Question 35.
Classify lipids. Give an example of each type.
Answer:
The following chart shows different types of lipids with one example of each.

Question 36
What is meant by simple lipids? Give example.
Answer:
The lipids which are composed of esters of different fatty acids and glycerol only, are called simple lipids. Example-Lanoline, Wax etc.

Question 37.
What is meant by conjugated lipids? Give example.
Answer
Certain types of lipids are composed of some other substances beside fatty acids and glycerol, these are called conjugated lipids. Example-Phospholipid, Glycolipid etc.

Question 38.
What is meant by derived lipids? Give example.
Answer:
Derivatives of lipids or biologically active lipid-like compounds, are called derived lipids.
Example-Prostaglandins, Steroids etc.

Question 39.
Mention the physical characteristic features of lipids.
Answer:
The physical characteristic features of lipids are as follows-

• Lipids are colourless, tasteless and odourless substances,
• Lipids are insoluble in water but soluble in organic solvents like ether, benzene, chloroform etc.
• Due to low specific gravity all lipids float in water.

Question 40.
Mention two importances of lipid in a living organism.
Answer:
Two importances of lipid in a living organism are as follows-

• Lipids are the reserve food materials of plants and animals.
• Lipid is one of the main structural components of cell membrane.

Question 41.
What is meant by fat? Give example.
Answer:
The triglycerides which remain in solid or semi-solid state at room temperature, are called fat. One example of plant fat is margarine and that of animal fat is butter.

Question 42
What is meant by wax? Give example.
Answer:
Wax is a solidified ester of a fatty acid and an alicyclic or aliphatic monohydric alcohol other than glycerol. Example-Lanoline, Bee-wax etc.

Question 43.
What is meant by organic oil? Give example.
Answer:
The glycerides which are hydrophobic, lipophilic, slippery substances, with low melting points and remain in liquid state at room temperature, are called organic oils. ExampleCoconut oil, mustard oils etc.

Question 44.
What is nucleoside?
Answer:
Nucleoside is an elementary part of a nucleic acid composed of any one of the purines or pyrimidines bases and a pentose sugar of either ribose or deoxyribose type.

Question 45
What is meant by nucleic acid? Give example.
Answer:
The largest biological macromolecule, composed of several nucleotides, occuring in all living cells for storing and transmitting hereditary characters and genetic information, is known as nucleic acid. Example-Deoxyribonucleic acid (DNA) and ribonucleic acid (RNA).

Question 46
Classify different types of nitrogenous bases found in nucleic acids.
Answer:
The following chart shows different types of nitrogenous bases found in nucleic acids.

Question 47.
Where does DNA occur?
Answer:
DNA occurs inside the protein capsule of DNA-virus. In eukaryotic cells, it is present in chromosomes within the nucleus. It is also present in the matrix of their mitochondria and plastids. In prokaryotic cells, it is present as a circular DNA, but it lies naked in the cell cytoplasm in a specialised region called nucleoid.

Question 48.
Write two functions of DNA.
Answer:
Two functions of DNA are as follows-

• DNA transmits hereditary characters from parents to offspring.
• DNA controls all gene-regulated biological activities.

Question 49.
What is RNA?
Answer:
RNA is the ribose sugar containing single stranded bio-macromolecule, which acts as the genetic material in Ribovirus and helps DNA to perform its hereditary and genetic activities in eukaryotic cells as well as helps in protein synthesis.

Question 50
What are vitamins?
Answer:
Vitamins are special components of food which are present in very little quantities, but they perform an elementary role in various physiological activities and in development of immunity against different diseases. Examplesvit. A, vit. B, vit. C, vit. D, vit. K etc.

Question 51.
What is meant by anti-vitamins? Give an example.
Answer:
Certain organic compounds hinder the functions of some vitamins or denature some vitamins completely. These compounds are known as anti-vitamins. Example-Galactoflavin is an anti-vitamin, which hinders the action of vitamin B₁₂ or riboflavin.

Question 52.
What is a pseudo-vitamin? Give an example.
Answer:
A pseudo-vitamin is a substance that has a chemical structure similar to that of a vitamin but lacks the usual physiological effects of a vitamin. Example-Methylcobalamin is the pseudovitamin of vitamin B₁₂

Question 53.
What is a provitamin? Give an example.
Answer:
The organic compound from which vitamin is synthesised in the body of a living organism, is called a provitamin. Example-vitamin A is synthesised in the liver from the provitamin β Carotene.

Question 54.
Mention the functions of vitamin A in human body.
Answer:
The functions of vitamin A in human body are as follows-

• Vitamin A helps to maintain health of eye, tear gland and retina.
• It helps in maintaining healthy skin and muscle.

Question 55
Why vitamin A is called anti-xerophthalmic vitamin?
Answer:
Xerophthalmia is defined as the condition characterised by excessive and abnormal dryness of the eye-ball, accompanied by conjunctivities. This occurs basically due to the deficiency of vit.A. Since, vit.A prevents Xerophthalmia, therefore it is called anti-xerophthalmic vitamin.

Question 56.
Mention the functions of vitamin D in human body. Mention its sources.
Answer:
Functions:

• Vitamin D helps in the uptake of phosphorus and calcium from the intestine.
• It helps in the formation of teeth and bones.

Sources: The sources of vit.D are milk, cabbage, vegetable oil, cod liver oil etc.

Question 57.
Why vitamin D is called anti-ricketic vitamin?
Answer:
Ricket is a vit.D deficiency disease. Since vit.D helps in the prevention of the disease, therefore it is called as anti-ricketic vitamin.

Question 58.
Which vitamin is called anti-sterility vitamin? Mention the main functions of this vitamin.
Answer:
Anti-sterility vitamin: Vitamin E is called antisterility vitamin
Functions of vitamin E:

• Vitamin E helps in the development of embryo, reproductive organs and muscles.
• It helps to inhibit unwanted oxidation in the body by substances called free radicals.

Question 59
Which vitamin is called anti-haemorrhagic vitamin? Mention the functions of this vitamin.
Answer:
Anti-haemorrhagic vitamin: Vitamin K is called the anti-haemorrhagic vitamin.
Functions of vitamin K:

• Vitamin K helps in prothrombin formation and blood coagulation.
• It helps in the normal energy production in mitochondria.

Question 60
Which vitamin is called anti-scorbutic vitamin? Mention the functions of this vitamin.
Answer:
Anti-scorbutic vitamin: Vitamin C is called antiscrobutic vitamin, since it helps in preventing the disease scurvy.
Function of vitamin C:

• It protects the body against some infections like common cough and cold.
• It helps in the development of teeth and bones.
• It catalyses the metabolism of carbohydrates.

Question 61
Mention the functions of vitamin B₃.
Answer:
The functions of vitamin B₃ are as follows:

• It catalyses the transformation of carbohydrates to lipids.
• It helps to stimulate the central nervous system.
• It helps in cellular respiration and metabolism.

Question 62
Which two vitamins help in cellular respiration? What is the similarity between iron and vitamin B₁₂ ?
Answer:
Both vitamin B₁ and B₂ help in cellular respiration.
Both iron and vitamin B₁₂ help in the formation of red blood cells.

Question 63.
Mention one function of chlorine. Write a function of manganese.
Answer:
Function of chlorine: Chlorine helps to maintain the acid-base balance in the body.
Function of manganese: Manganese regulates the normal level of carbohydrate in the blood.

Question 64.
How do minerals control membrane permeability?
Answer:
Potassium (K) increases membrane permeability of living cells whereas calcium (Ca) restricts it. Thus, mineral elements play important role in controlling membrane permeability in the body.

Question  65
Write the names of some plant and animal sources of food which are rich in magnesium.
Answer:

• Plant sources of magnesium: The plant sources of magnesium are green vegetables, grains, groundnut, bean, soyabean, peas etc.
• Animal sources of magnesium: The animal sources of magnesium are fish, chicken, egg, milk etc.

Question 66.
Write the names of some plant and animal sources of food which are rich in iron.
Answer:
Plant sources of iron: The plant sources of iron are pulses, whole-wheat flour, spinach, lettuce, banana etc.
Aninal sources of iron: The animal sources of iron are fish, egg, mutton, liver etc.

Question 67.
Which elements and vitamins help in the formation of our skeletal structure?
Answer:
Calcium (Ca) and phosphorus (P) are the main building components of bones and teeth. Similarly, vitamin D and vitamin C are the vitamins which also help in the formation of teeth and bones. Thus, these elements and vitamins take part in the formation of the skeletal structure of the human body.

Question 68
Mention two animal sources and a plant source of calcium.
Answer:
Two animal sources of calcium are fish and egg and a plant source of calcium is peas.

Question 69
What are the functions of sodium in human body?
The functions of sodium in human body are as follows-

• It helps to maintain cardiac systole, blood pressure, blood volume and acid-base balance.
• It helps in the flow of nerve impulse.
• It also helps to maintain the density of urine.

Question 70.
Mention a plant source and an animal source of sodium.
Answer:
A plant source of sodium is vegetables and an animal source of sodium is butter.

Question 71.
Distinguish between oligosaccharides and polysaccharides.
Answer:

Features	Oligosaccharides	Polysachharides
1. Number of monosaccharide units	Made up of 3-9 monosaccharide units	Made up of 10 or more than 10 monosaccharide units
2. Solubility	Soluble in water	Insoluble in water
3. Taste	Sweet	Tasteless

Question 72.
Distinguish between amino acids and fatty acids.
Answer:

Features	Amino acids	Fatty acids
1. Occurence	Structural unit of proteins	Structural unit of lipids
2. Chemical structure	Each molecule has one amino (-NH2) and one carboxylic (-COOH) group	Each molecule has one methyl (-CH2) and one carboxylic (-COOH) group and one intermediate ethyl (-CH2) group
3. Function	Join with polypeptides to synthesise enzymes, hormones and to form cell components	Prepare different membranes of cell and cell organelies. Participate in lipid synthesis.

Question 73.
Distinguish between simple carbohydrates and complex carbohydrates.
Answer:

Features	Simple carbohydrates	Complex carbohydrates
1. Number of monosaccharide units	Made up of one or two monosaccharide units	Made up of more than two monosaccharide units
2. Nutritional value	Quickest source of energy, lack fibre	Rich in fibre, vitamins and minerals
3. Biological significance	Get oxidised in respiration to generate energy	Build cellular membranes and act as stored food

Question 74.
Distinguish between nucleotides and nucleosides.
Answer:

Features	Nucleotides	Nucleosides
1. Structural components	Pentose sugar, nitrogenous base and phosphate	Pentose sugar and nitrogenous base
2. Nature	Acidic	Slightly basic
3. Role	Structural unit of nucleic acids	Structural portion of a nucleotide

Long Questions and Answers : (5 marks for each question)

Question 1.
Briefly describe the role of water in a living body. Mention the importance of different gases and salt in living organisms.
Answer:
Role of water in living body
The role of water in living body are as follows—

• Body of a living organism consists of 70-90% water. Water acts as the medium of all cellular reactions within protoplasm.
• In plants, water helps in photosynthesis, ascent of sap, germination of seeds and transpiration.
• In animals, water is the major component of body fluid. It helps in digestion, excretion and maintains salt and water balance.
• In squids and echinoderms, water helps in locomotion also.

Importance of different gases in living organisms
Oxygen and carbon dioxide are the two most biologically important gases. Their importance are as follows—

• Oxygen is essential for respiration in all aerobic organisms to oxidise food and to liberate energy.
• Carbon dioxide is the raw material, utilized by all the autotrophs for photosynthesis.

Importance of salt in living organisms
The importance of salt in living organisms are as follows—

• Salt maintains osmoregulation in body.
• Salt controls the production of thyroid hormone.
• Salt helps to form structure of bones.

Question 2.
Briefly mention the main characteristic features of carbohydrates and its importances in living body.
Answer:
Main characteristic features of carbohydrate

The main characteristic features of carbohydrates are mentioned below.

• Carbohydrates are colourless, odourless and mosdy water-soluble (polysaccharides are insoluble in water) organic compounds.
• Smaller carbohydrates (monosaccharides and disaccharides) are sweet tasting, hence, they are known as sugars.
• Carbohydrates behave as reducing molecules due to presence of aldehyde and ketone in them.
• In larger carbohydrate molecules, monosaccharide units may arrange in either linear or circular manner.

Importance of carbohydrates in living body

The importance of carbohydrates in living body are as follows —

• Monosaccharides (glucose and fructose) act as fuel to fulfill body’s energy need. Calorific value of carbohydrate is 4.1 kcal/g.
• Structural components of cell wall, cell-coat and blood group antigens are carbohydrates.
• Glucose and other sugars are transformed into fats and amino acids by some physiological processes.
• Most animals are incapable of digesting cellulose. So it is accumulated in the intestine as roughage, which in turn, helps in bowel formation.

Question 3.
Classify monosaccharides based on the number of carbon atoms. Mention the characteristic features of monosaccharides.
Classification of monosaccharides
Based on the number of carbon atoms, monosaccharides can be classified into the following types.

• Triose: These monosaccharides are composed of three carbon atoms. Example-Glyceraldehyde.
• Tetrose: These monosaccharide molecules have four carbon atoms. Example-Erythrose.
• Pentose: Five carbon atoms are present in a pentose monosaccharide. Example-Ribose.
• Hexose: This is the most commonly occuring monosaccharide, which is composed of six carbon atoms. Example-Glucose, fructose etc.
• Heptose: Few monosaccharides are of this type, which have seven carbon atoms.
  Example-Sedoheptulose.

Characteristic features of monosaccharides
The characteristic features of monosaccharides are as follows-

• These are crystalline solids at room temperature and quite soluble in water. Monosaccharides are colourless, sweet substances.
• These are reducing sugars, reduces mild oxidising agents because they have free ketone or aldehyde group.
• These produce glycoside bond when react with alcohol and form enediol compound when react with base.

Question 4.
How do proteins take part in different life processes?
Answer:
Role of proteins in different life processes
Proteins take part in different life processes. These are mentioned below.

• Proteins are the building materials of a living cell.
• Proteins are directly involved in the development of embryo, growth, healing of wounds, repair of damaged tissues etc.
• Proteins are the main structural components of animal cell membrane and cell organelles, different body tissues, different enzymes, hormones and antibodies and several other substances.
• Nucleoproteins constitute chromosomes, which carry genes.
• Protein is also a major source of energy. Calorific value of protein is 4.1kcalg.
• Broken non-nitrogenous amino acids produce carbohydrates and fats by the process of deamination and trans-amination.
• Proteins act as buffer solution to maintain the pH of body.
• In mammals, proteins play important role in production of milk during lactation.

Question 5.
Schematically represent different types of proteins. Give a brief account of different proteins based on nutritional value. Mention the sources.
Answer:
Schematic representation of different types of protein

Different proteins based on nutritional value

Nutritional value of proteins depends upon the number of essential amino acids present in it.

• First class protein: The proteins which contain all essential amino acids in perfect proportion Sources of protein necessary for building our body are treated as first class proteins. Sources-Different animal proteins like milk, meat, fish, egg etc.
• Second class proteins: The proteins which may contain essential amino acids but not in perfect proportion, which is necessary for building the body, or lack a few essential amino acids, are known as second class proteins. Sources-Pulses, gram, rice, wheat etc.
• Third class proteins: These proteins do not contain essential amino acids, hence, play no role as body building material, these are merely catabolised to generate heat. Source-Gelatin.

Question 6.
Mention the role of essential fatty acids in our body.
Answer:
Role of essential fatty acids
The role of essential fatty acids in our body are mentioned below.

• Essential fatty acids are responsible for keeping the skin glowing and wrinkle-free.
• These help in maintaining membrane permeability of skin cells.
• These help in maintaining steady supply of milk in mammary glands of lactating mothers.
• Essential fatty acids help to maintain water balance in the body.
• These fatty acids help in growth and extend reproductive life.
• These help in transporting cholesterol in blood.
• Function of kidney is further supported due to the presence of some essential fatty acids.

Question 7.
Mention two biological importance of fatty acids. Write down the roles of lipids in life processes.
Answer:
Importance of fatty acids
Two biological importance of fatty acids are as follows-

• Fatty acids are the units of fat, which is one of the most important structural components of the body.
• Products of many fatty acids act as hormones.

Roles of lipids in life processes
The roles of lipids in life processes are as follows-

• Lipids act as the reserve food materials of plants and animals.
• Fat can generate maximum heat energy. Its calorific value is 9.3kcalg. Animals like frogs, snake etc. store fat in the adipose cells under their skin, which protect them against extreme cold.
• Fat deposits in the body of desert animals (such as camels) are oxidised to produce metabolic water, to counter extreme dryness.

Question 8
Describe the structure of a nucleotide. Mention the main roles of nucleotides in life processes.
Answer:
Structure of nucleotide
Nucleotides are the units of nucleic acids. Several nucleotide monomers join in a linear sequence to constitute a nucleic acid molecule. A nucleotide is composed of three components-

• A pentose (5C) sugar,
• A nitrogenous base and
• A phosphate group.

A nucleotide monomer without phosphate is called nucleoside. Practically, A phosphate group holds two successive nucleosides together. Nucleotides have two basic types of nitrogenous bases-

• Purines (include adenine and guanine)
• Pyrimidines (include thymine, cytosine and uracil).

Pentose sugar is also of two types-

• ribose and
• deoxyribose.

Roles of nucleotides in life processes
The main roles of nucleotides in life processes are as follows-

• Nucleotides play an important role in cell signalling and metabolism.
• The specific arrangement of nucleotides on a nucleic acid stores genetic information for performing all the biochemical activities in all living organisms.

Question 9.
Schematically represent the different components of a DNA molecule. Briefly describe the structure of a DNA molecule.
Answer:
Components of a DNA molecule

Structure of a DNA molecule
A DNA molecule is a double-stranded, coiled, helical structure, running in opposite directions and made up of a several nucleotide units. Many nucleotide monomers join in a linear sequence in two parallel strands to constitute a DNA molecule. The structural unit of DNA is composed of a sequence of deoxyribonucleotides. Such a nucleotide is composed of three components-

• A five carbon containing deoxyribose sugar,
• Any one of the four nitrogenous bases (viz. adenine, guanine, thymine and cytosine) and
• A phosphate group. Practically, two successive nucleosides are held together by a phosphate group to constitute a DNA strand.

The two strands of a DNA molecule are zipped together by weak hydrogen bonds. Here, adenine joins with thymine by two hydrogen bonds (A=T) and guanine joins with cytosine by three hydrogen bonds (G≡C).

Question 10.
Mention the similarities and dissimilarities of DNA and RNA.
Answer:
Similarities between DNA and RNA
The similarities between DNA and RNA are as follows-

• Both DNA and RNA are nucleic acids.
• Both are made up of pentose sugar, nitrogenous base and phosphate.
• Both are treated as bio-macromolecules.
• DNA and RNA carry same types of purines, i.e. adenine and guanine.
• Cytosine is present in both these molecules.

Dissimilarities between DNA and RNA

Features	DNA	RNA
1. Occurrence	Nucleus, mitochondria and plastids	Cytopasm and ribosomes
2. Physical structure	Double stranded helical molecule	Single stranded molecules with some loops
3. Type of sugar	Deoxyribose sugar	Ribose sugar
4. Nitrogenous base	Adenine, guanine, thymine and cytosine	Adenine, guanine, uracil and cytosine
5. Genetic activity	Acts as the genetic material in all living cells	Acts as the genetic material in some viruses
6. Function	Give all genetic commands to control every reaction and activity in a living cell or a living body	Helps in synthesis of polypeptide chains according to the command of DNA

Question 11.
What is atherosclerosis? Mention the effects of fluorine overdose in human body.
Answer:
Atherosclerosis
When cholesterol percentage becomes excessive in blood, cholesterol is deposited and forms plaque on the inner wall of arteries. Thus, the arterial wall becomes thick. This condition is called as atherosclerosis. Atherosclerosis enhances the chances of heart failure.

Effects of fluorine overdose in human body
Presence of excess fluorine in drinking water has harmful effects on the teeth. The enamel of the teeth becomes weak and turns brownish in colour. It also results in the formation of cavity leading to a condition called dental fluorosis.

Apart from this, fluorine forms a cementing layer on spine and bones of legs, resulting in the loss of their natural flexibility. In addition to this, high fluoride ingestion can also cause a range of gastro-intestinal symptoms like nausea, pain and vomiting. Moreover, excess fluoride level in body results in polyuria (frequent urination), polydipsia (excessive thirst) and constipation followed by diarrhoea.

Question 12
Mention the role of different types of vitamin B in human body.
Answer:
Role of vitamin B in human body
Role of different types of vitamin B in human body are as follows-

1. Vitamin B₁ (Thiamin):

• It helps in the oxidation of sugars in brain and muscular tissues.
• It catalyses the synthesis of proteins, fats and carbohydrates.
• It helps in general growth of the body.

2. Vitamin B₂ (Riboflavin):

• It helps in cellular respiration.
• It helps in maintaining healthy skin.
• It catalyses the transformation of carbohydrates into fat.

3. Vitamin B₃ (Nicotinic acid or Niacin):

• It catalyses the transformation of carbohydrates into lipids.
• It helps to stimulate the central nervous system.
• It helps in cellular respiration and metabolism.

4. Vitamin B₅ (Pantothenic acid):

• It helps in the production of neurotransmitters in the body.
• It helps to relieve the human body from a number of detrimental problems, like asthma.
• It helps to prevent several neural problems like insomnia, depression etc.

5. Vitamin B₆ (Pyridoxine):

• It catalyses the transformation of starch and proteins into fat.
• It helps in the synthesis of haemoglobin.
• It helps in protein metabolism.

6 Vitamin B₉/M (Folic acid):

• It helps to produce healthy RBCs.
• It helps in DNA formation.
• It helps to maintain pregnancy and reduces the chance of premature delivery.

7. Vitamin B₁₂ (Cyanocobalamine):

• It helps in hemopoiesis or formation of RBC.
• It catalyses the synthesis of nucleic acid.
• It helps to maintain normal growth and activity of nervous system.

Question 13.
Differentiate between water-soluble vitamins and fat-soluble vitamins.
Answer:
Differences between water-soluble vitamins and fat-soluble vitamins

Features	Water-soluble vitamins	Fat-soluble vitamins
1. Absorption medium	Vitamins get dissolved in water and are absorbed through blood	Vitamins get dissolved in fat and are absorbed through blood
2. Storage	These vitamins get stored according to the need of the body	These vitamins get stored in the body in excess quantity and cause hypervitaminosis
3. Necessity	These vitamins should be taken regularly with food	These vitamins remain stored in the body and utilised whenever need arises
4. Wastage	During cooking, heat results in partial destruction, or, wastage of these vitamins	During cooking, wastage or destruction of these vitamins is much less than that of water-soluble vitamins
5. Example	Vitamin B-complex, vitamin C, vitamin P	Vitamin A, vitamin D, vitamin E, vitamin K

Question 14.
Mention the various functions of amino acids. What is biological value of protein?
Answer:
Various functions of amino acids
The various functions of amino acids are as follows-

• Formation of protoplasm: Amino acids help in the formation of protoplasm in living cells. They also help in the production of proteins like elastin, keratin etc.
• Regulation of chemical reactions: Amino acids help in the synthesis of enzymes and also regulate different essential chemical reactions in the body.
• Formation of haemoglobin: They also help in the proper formation of haemoglobin.
• Antibody production: Amino acids help to produce antibodies in the body, which fight against many disease causing germs.
• Glucose formation: They heip in the formation of glucose by the process of gluconeogenesis.

Biological value of protein
Biological value of protein is a measure of the proportion of absorbed protein from a food, which becomes incorporated into the proteins of the organism. In adults, total protein consumed is not utilised in body building, instead, it is used in healing and rest is removed through excretion. The part of protein which is assimilated after absorption in the body, is the biological value of protein.

It is measured with the following formula-
\(\text { Biological value of protein }=\frac{\text { Nitrogen incorporated into the body on the test day }}{\text { Nitrogen absorbed in proteins on the test day }} \times 100\)

Question 15.
What do you understand by the terms macroelements and microelements? Mention general role of different minerais on physiological process of human body.
Answer:
Macroelements
The elements, which are required in large quantities for proper growth and development of human body, are known as macroelements. Example-Sodium (Na), potassium (K), chlorine (Cl), calcium (Ca), phosphorus (P) etc.

Microelements
The elements, which are required in minute quantities for proper growth and development of human body, are known as microelements. Example-Iron (Fe), boron (B), iodine (I), molybdenum (Mo), zinc (Zn), manganese (Mn), copper (Cu) etc.

General role of different minerals in human body
Different minerals play different roles on physiological processes, which are as follows-

• As cofactors of enzymes: Different minerals like iron, copper, manganese, zinc etc. act as cofactors of the enzymes.
• Maintenance of acid-base balance: Certain elements like sodium, potassium, chlorine etc. maintain acid-base balance within the body.
• Maintenance of water balance: Sodium helps in maintaining water balance within the body.
• Conduction of nerve impulse: Sodium and potassium play very important role in the conduction of nerve impulse.
• Control membrane permeability: Elements like calcium and potassium control membrane permeability of our body.
• Role in blood coagulation: Calcium acts as an essential blood-coagulating factor.
• Formation of skeletal structure: Calcium and phosphorus are the main building components of bones and teeth.

Detailed explanations in West Bengal Board Class 9 Life Science Book Solutions Chapter 5.2 Natural Resources and its Sustainable Use offer valuable context and analysis.

WBBSE Class 9 Science Chapter 5.2 Question Answer – Natural Resources and its Sustainable Use

Very Short Questions and Answers : (1 mark for each question)

Question 1.
Name two natural resources.
Answer:
Two natural resources are forest and water.

Question 2.
What are the types of natural resources?
Answer:
Natural resources are of two types-

1. Renewable natural resources
2. Nonrenewable resources.

Question 3.
Name two renewable natural resources.
Answer:
Two renewable natural resources are water and wind.

Question 4.
Name two non-renewable natural resources.
Answer:
Two non-renewable natural resources are coal and petroleum.

Question 5.
In West Bengal, what percentage of land is under forest cover?
Answer:
16.5. % of West Bengal is covered by forest.

Question 6.
What percent of the total area of a country should be under forest cover?
Answer:
33 % of the total area of a country should be under forest cover.

Question 7
Name one economically important forest product.
Answer:
Wood is an economically important forest product.

Question 8.
Name some products, which we get from the forest.
Answer:
We get honey, timber, latex, resin etc. from forest.

Question 9.
What is the best way to conserve biodiversity?
Answer:
Afforestation is the best way to conserve biodiversity.

Question 10.
What is the medicinal utility of forest?
Answer:
Forest comprises several varieties of medicinal herbs, from which medicines are obtained.

Question 11.
What is the main cause of deforestation?
Answer:
Human population explosion is the main cause of deforestation.

Question 12.
Write down one natural cause of deforestation.
Answer:
Forest fire is a natural cause of deforestation.

Question 13.
Write down one man-made cause of deforestation.
Answer:
Urbanisation is a man-made cause of deforestation.

Question 14.
Which is the ‘natural buffer’ of an environment?
Answer:
Forest is the ‘natural buffer’ of an environment.

Question 15.
How much water on the earth do we get as freshwater?
Answer:
Only 2 % of the total water on the earth is utilised as freshwater.

Question 16.
In which two states of India, rain water harvesting is necessary.
Answer:
In Rajasthan and Gujrat, rain water harvesting is necessary.

Question 17.
By which natural process, earth gets freshwater?
Answer:
Earth gets freshwater in the form of rain.

Question 18.
Which branch of economic botany includes the cultivation of medicinally important herbs?
Answer:
Cultivation of medicinally important herbs is included under horticulture.

Question 19.
In Gangetic plains, which is the main source of dietary protein?
Answer:
Fish is the main source of dietary protein in the Gangetic plains.

Question 20.
Which decade was famous for green revolution?
Answer:
The decade of nineteen sixties was famous for green revolution.

Question 21.
Name of the food products of animal husbandry.
Answer:
The food products of animal husbandry are meat, milk and egg.

Question 22.
Name two edible mushrooms.
Answer:
Name of two edible mushrooms are Agaricus bisporus and Boletus edulis.

Question 23.
Mention one cause of global food crisis.
Answer:
Population explosion is an important cause of global food crisis.

Question 24.
Give some examples of fossil fuel.
Answer:
Some examples of fossil fuel are coal, petroleum, natural gas, mineral oil etc.

Question 25.
Mention one process of energy conservation in daily life.
Answer:
Using LED bulbs instead of ordinary bulbs reduces energy consumption atleast by \(\frac{2}{3}\) times.

Short Questions and Answers : (2 marks for each question)

Question 1.
What is meant by natural resources?
Answer:
Natural resources are those components, which occur in nature, are invaluable for humans and on which our survival depends.

Question 2.
What is meant by sustainable development?
Answer:
Sustainable development is the developmental process that meets the demand of the present, without destroying the scope of the future generation to meet their needs. In this process, industrial, agricultural and other developmental processes are carried out without causing any harm to the environment.

Question 3.
Why is sustainable development necessary?
Answer:
The natural resources that are present in our environment are continuously being utilized to maintain human lifestyle. With the advancement of human civilization and increase in population, these resources are being misused and wasted, rather than utilized. As a result, scientists and environmentalists have been trying to adopt measures to conserve these resources and save the environment, and subsequently carrying out all activities necessary for human development. For this reason, sustainable development is necessary.

Question 4.
What do you mean by forest?
Answer:
A forest is defined as a large area of land, that is covered with trees as well as other woody and non-woody vegetation. Forests are the predominant terrestrial ecosystem of earth and are distributed across the globe.

Question 5.
Why is forest considered as a resource?
Answer:
Forest plays important roles in improving the socio-economic condition of a country. They are-

1. Forest serves as a source of raw materials for various industries.
2. Forest serves as an important source of timber, which is used for making houses, furniture, boats etc.
3. Forest serves as an important source for honey, latex, resin and other medicinal plants.
4. Forest plays an important role in the conservation of biodiversity, regulation of climate and prevention of soil erosion. For these reasons forest is considered as an important natural resource.

Question 6.
What is meant by forest conservation?
Answer:
Forest conservation is the practice of maintaining forested areas for the benefit and sustainability of future generations. By this process over-utilization and improper use of forest resource is prevented and the biodiversity is conserved as well.

Question 7.
What is water cycle?
Answer:
Surface water from seas, lakes etc. evaporates to form water vapour and rises upwards. Transpiration by plants also contributes to this. This water vapour mixes with dust particles and combine with each other to form clouds. The clouds precipitate on the earth as rain, which mixes with rivers and streams and ultimately reverts back to sea. This continuous cyclic flow of water is known as water cycle.

Question 8.
Write down two important effects of water cycle?
Answer:
Two important effects of water cycle are[1] It maintains water balance between landmass and water bodies. [2] It maintains the supply of drinking water and surface water.

Question 9.
What is ground water?
Answer:
The water present beneath the surface of the earth in the tiny spaces between soil particles to large fractures of rocks, is known as groundwater.

Question 10.
What is drinking water?
Answer:
The water that is safe enough for drinking and food preparation and does not cause any harm to human being, is known as drinking water. Drinking water is also known as potable water.

Question 11.
What do you mean by over-utilization of water?
Answer:
The water, collected from the surface and underground sources, are often misused or used indiscriminately. This is known as over-utilization of water.

Question 12.
Give examples of over-utilization of water.
Answer:
Over utilization of water occurs in many ways, such as-

1. While brushing teeth, bathing and washing, leaving the tap running.
2. In urban areas, fresh water is suctioned from underground much more than its normal demands, thereby lowering the underground reserve of fresh water.
3. Agricultural fields are irrigated with underground water.
4. Large amount of water is exploited in various industries.

Question 13.
Mention two causes of lowering of ground water level.
Answer:
Two causes of lowering of groundwater level are-

1. The groundwater is suctioned in large quantity by means of motor pumps in order to meet human demands.
2. In rural areas, huge quantity of groundwater is being used for irrigation.

Question 14.
Why is rain water considered pure as compared to the water of other water hodies?
Answer:
Only the water particles present on the surface of water bodies evaporate and accumulate to form clouds, which comes down as rain. The mineral salts or the harmful pollutants present in the water bodies do not evaporate to form clouds. As a result, these harmful particles do not come down with rain. So, rain water is considered pure as compared to the water of other water bodies.

Question 15.
What is meant by agriculture?
Answer:
Scientific practice of farming, including cultivation of soil for growing economically important crops and rearing of animals for food, wool, silk and other products, is called agriculture.

Question 16.
What is meant by horticulture?
Answer:
Horticulture is a branch of agriculture that includes the cultivation of fruits, vegetables, seeds medical plants, mushrooms, ornamental plants.

Question 17.
What is meant by pisciculture?
Answer:
Pisciculture is a branch of agriculture that deals with the scientific practice of breeding, rearing and marketing of fish, prawn and other economically important aquatic animals.

Question 18.
What is poultry farming?
Answer:
Poultry farming is a branch of agriculture that deals with the scientific practice of breeding and rearing of birds like chicken, duck, quail, turkey etc. for meat and egg.

Question 19.
What is meant by animal husbandry?
Answer:
Animal husbandry is the branch of agriculture that deals with the scientific practice of breeding and rearing of farm animals (cattle, sheep, poultry birds).

Question 20.
What is meant by energy crisis?
Answer:
With the development of industry and upliftment of lifestyle, the utilization of energy has increased to a great extent. But the generation of energy has not been increased to meet up that demand. This situation has developed a worldwide problem, that is popularly known as energy crisis.

Question 21.
Mention two common examples of wastage of electrical energy.
Answer:
Examples of wastage of electrical energy are as follows-

1. Leaving the rooms, office, classrooms etc. vacant with fans and lights switched on.
2. Keeping the street lights switched on duing the daytime.

Question 22.
What do you understand by energy resources?
Answer:
Energy resources are the main sources of energy from which energy can be extracted and utilized for mankind.

Question 23
What is a renewable natural resource?
Answer:
The renewable natural resources are those, which may drop quantitatively after being harvested but are replenished naturally after a certain period of time. Examples-Trees of forest, Population of fish etc.

Question 24.
What is a non-renewable natural resource?
Answer:
The non-renewable natural resources are those, which drop quantitatively after utilization and are never replenished by means. ExamplesCoal, Petroleum etc.

Question 25.
How different natural resources are intimately connected with our existence on earth?
Answer:
Forests, water, food and energy are the basic resources offered by nature. Forest acts as the habitat of life. It provides shelter to thousands of living organisms. Water is the main substance of life. Without water, no organism can survive. Food is the fuel of life, which provides energy, that perpetuates life. Thus, natural resources are intimately connected with our survival on earth.

Question 26.
What is White revolution?
Answer:
To achieve sustainability in milk production, advanced cattle breeding programme has been undertaken. This programme is called operation flood. Now this drive has shown its success. This is known as white revolution.

Question 27.
What is Blue revolution?
Answer:
To achieve the target of feeding the growing population of India, modern techniques of fish culture have been developed. This programme is popularly known as blue revolution, which has successfully reached its goal.

Question 28.
What is Green revolution?
Answer:
In the middle of sixties, in order to achieve sustainability in crop production, intensive agricuitural management has been practiced by applying hybrid crops, proper application of

Question 29.
fertilisers, agricultural equipments, proper irrigations etc. This is known as green revolution.
What is meant by food?
Answer:
The edible matters, which are taken in by the living organisms for nutrition, growth, generation of heat for physiological processes and to develop immunity against diseases, are collectively called food.

Question 30.
What is SCP?
Answer:
Single cell protein (SCP) refers to the sources of mixed protein that has been extracted from pure or mixed culture of various microorganisms (such as algae, fungi or bacteria) and are used as protein-rich foods for human beings and animals. Example-Spirulina.

Long Questions and Answers : (5 marks for each question)

Question 1.
Discuss the environmental and economic importance of a forest.
Answer:
Importance of a forest :
Importance of a forest is described below.
1. Watershed protection: Afforestation along the slope of watershed prevents runoff and reduces the deposition of slit in riverbed. Some plants with mycorrhizal root absorb heavy and toxic metals from soil and reduce the chance of water toxicity.

2. Atmospheric regulation: Scarcity of plants and excessive industrialization in urban areas reduces O₂ and increases CO₂ content in the atmosphere. Forest regulate O₂-CO₂ balance. By respiration organisms release CO₂ and absorb O₂ from the atmosphere. By the process of photosynthesis, green plants of a forest release O₂ and absorb CO₂. In this way, balance of O₂ and CO₂ in the atmosphere is maintained.

3. Erosion control: Erosion means washing or blowing away of top layer of soil. Forests prevent soil erosion by several methods. They are-

• The branches of roots firmly bind the soil particles with the ground.
• The dense leaves of forest prevent raindrops from hitting the soil particles directly and loosening it from the upper layer of soil.
• The litter formed by the leaves on the forest floor, partly decompose to form sticky humus. This sticky humus increases the adhering capacity of the soil particles and prevents soil erosion.

4. Local use: Humans exploit forest in different ways. People living in nearby villages collect firewood from forest. Forest provide honey, timber, resin, honey, cotton, fur, wool, meat (from herbivores) etc. that are collected and marketed.

5. Productive use: From productive point of view, forest has immense importance. Timber is the main economically important product of forest, used to prepare sleepers, posts, log houses, plywood, laminates, galleries, furniture etc. Ecotourism is another productive aspect of the forest, from which the government earns huge amount of revenue. Honey, rubber and several medicinally important materials are collected from the forest.

Question 2
Briefly discuss the causes of deforestation.
Answer:
Causes of deforestation :
The different causes of deforestation are discussed below-
1. Subsistence agriculture: It is an unscientific method of farming, where farmers concentrate on growing enough food for themselves and their family. They cut trees and burn smaller vegetation to prepare land for cultivation and cattle grazing.

2 Indiscriminate felling of trees: Growing population has increased demand of wood products, starting from match-sticks to furniture. Accordingly, price of wood has also been increased. Due to this high price of wood, traders encourage indiscriminate felling of trees.

3. Urbanisation: For development of the state infrastructure, roads and railway tracks are laid through forestland. Moreover, miners acquired the forestland for oil, coal and ore mining. This level of human intervention has affected the lifestyle of both animals and plants and leads to habitat fragmentation.

4. Forest fire: In drier seasons, the local farmers and forest communities burn dry grasses to expand grazing area. High concentration of oxygen in forest atmosphere drives this small fire into a firestorm. It goes out of control and destroys hundreds of trees and many smaller and bigger wild animals.

5. Desertification: Rivers and streams flowing through forestlands often carry industrial pollutants. These toxic materials cause soil pollution, which leads to polluting forest ecosystem.

Question 3.
Describe the consequences of deforestation.
Answer:
Consequences of deforestation :
Consequences of deforestation are as follows-
1. Global warming: Due to deforestation and rapid pace of industrialisation, concentration of greenhouse gases like CO₂ increases in the atmosphere. This results in global warming.

2. Climatic change: Transpiration by trees increases humidity in atmosphere, which in turn enhances the chance of rainfall. In many parts of the world, rate of rainfall has dropped significantly due to deforestation.

3 Change of soil character and erosion: The litter, deposited in forest floor, decomposes to form humus, that keeps the soil healthy and moist in normal situation. Due to deforestation, soil gets exposed to sun and dries out. Moreover, soil particles become loose without binding of roots. Due to this, rain and wind washes off and blow away soil particles, reduce chance of humification resulting in soil erosion.

4. Flood and drought: Incidence of flood and drought has increased in every part of the world due to deforestation.

5. Wildlife extinction: Forests provide habitat for millions of species of flora and fauna. Deforestation makes them homeless. As a result, certain number of species as well as part of wildlife gets extinct.

6 Environmental pollution: Deforestation results in decrease in atmospheric oxygen level. At the same time carbon dioxide increases, which is a cause of air pollution. Mycorrhiza developing in the root system of some trees can remove heavy and toxic metals from the soil. In case of deforestation soil becomes polluted.

Question 4.
Why should we conserve forests? Mention few methods of forest conservation.
Answer:
Reasons of forest conservation
Conservation is protection, augmentation and scientific management of resources so as to maintain them in their optimum level providing benefit to the present as well as future generations. Forests must be conserved because of their immense economic, protective and regulative properties. Forest conservation is important-

• to maintain ecosystem of forest
• to maintain O₂ – CO₂ balance in the environment
• to maintain the supply of forest products like timber, food etc.
• to maintain natural beauty and livelihood of the local people.

Methods of forest conservation

1. Afforestation: It is growing of forests on unprotected barren lands.
2. Reforestation: It is developing forest cover in the area which has been damaged or cleared during exploitation.
3. Separation of commercial forestry: Useful plants required by industry should be planted separately preferably on waste land.
4. Grazing: Grazing should be regulated according to the availability of pasturage.
5. Social Forestry: It is growing of useful multipurpose trees and shrubs on common village lands, roadsides, railsides, etc. by cooperative efforts of people of the area. The plants provide fodder, small timber and fire wood to villagers.
6. Agroforestry: Multipurpose trees and shrubs are planted on the sides of crop fields to provide fodder, fuel and timber.

Both social forestry and agroforestry reduce pressure on the forests. Trees are also planted at all vacant place and along roads in urban areas (urban forestry) for reducing air and noise pollution.

Question 5.
Mention the uses of water. Briefly describe the causes of water scarcity. 2 + 3
Answer:
Uses of water :
Water is an essential component of life. Water is one of the most vital natural resources on Earth for life to sustain. The availability and the quantity of water have always played a significant part in determining not only where population can grow but also their quality of life. It is used in several ways.

1. Drinking: Water is the most essential and a universal drink necessary for life.
2 Agriculture and industrial purpose: A large quantity of water is used for irrigation of crop fields. Different industries, such as metal, paper, chemical, wood, petrochemical etc. and boilers of power plants require large quantity of water. Water is used as raw material, solvent, coolant and washing medium.

Causes of water scarcity :
The main causes of global water scarcity are-

1. Drop in rainfall: Rainfall has dropped radically in different parts of the world, resulting in moderate to severe water scarcity.
2. Global warming: Excessive heat dries out surface water. But this loss is not totally replenished by rain.
3. Over-utilisation of water: Over-utilization of ground water is a result of poor water management, that leads to water scarcity and increased chance of arsenic contamination.
4. Pollution: Disposal of sewage water in streams and lakes is a wasteful technique. By this process, sources of freshwater are polluted and wasted.

Question 6.
How is rain water utilised to counter scarcity of fresh water. Mention the advantage and disadvantage of rain water harvesting? 3 + 2
Answer:
Utilisation of rain water :
Rain water is the largest source of fresh water. By scientific harvesting of rain water, the fresh water scarcity can be controlled to a great extent. Rain water harvesting is a simple and effective method of water management by which rain water is collected, stored and used to meet the demand for fresh water.

The easiest and popular method is rooftop rain water harvesting. In this process, rain water : of roof are connected to a ground level or underground reservoir. The rain water is stored ; reservoir and is used according to necessity. This water can be used directly for any non-F purposes like watering plants, washing and cleaning, bathing and toilets. For cooking and dr this water must be disinfected and filtered. For using rain water at community level, resecreasing and disinfected centrally and then pumped to the overhead water supply tank or the main well of the village.

Advantages and disadvantages of rain water harvesting –
Advantages and disadvantages of rain water harvesting are as follows –
1. Advantages:

• Rain water is generally free from germs and contaminants.
• It is soft water with slightly acidic pH} and does not contain any salt.
• Rain water contains no corrosive substances, so it does not harm water pipes and reservoirs.

2. Disadvantages: Rain water harvesting is not practiced in areas with excessive suspended particulate matters in air. Toxic gaseous materials pollute the atmosphere at regions near chemical industries and fertilizer factories. These gaseous pollutants mix with rain water and make it harmful.

Question 7.
Briefly describe different sources of food for human consumption.
Answer:
Different sources of food for human consumption –
Different sources of food for human consumption are mentioned below-
1. Crop production: The maximum quantity of food we consume are plant products. These include cereals (paddy, wheat, maize, millets etc.), pulses (moong, masur, gram, pea etc.) and oil seeds (mustard seed, sunflower seed, groundnut seed, rape seed etc.)

2. Horticulture: Horticulture includes the cultivation of fruits, vegetables, nuts, seeds, herbs etc. We get fruits and vegetables from horticultural farms. The fruits and vegetables which we use in cooking, are also horticultural products.

3. Cattle farming: This industry is involved in breeding and rearing of animals like cows, goats, pigs etc. It provides us with animal products like meat and milk.

4. Poultry: This industry is involved in breeding and rearing domestic birds like chickens, ducks etc. This industry provides us with poultry producers like meat and eggs.

5. Fishery: Fisheries are meant for scientific breeding and rearing of fishes. Fisheries supplies fishes to our platter.

Question 8.
Briefly describe the situation of food scarcity on global basis. Mention the impacts of food scarcity on earth. 2+3
Answer:
Global food scarcity :

During the last century, industrialization and urbanization have reached the peak. This situation has pushed agriculture already at the back row. Now the rate of agricultural production cannot neet the global demand of food crops. The environmental changes and increasing population have ggravated this problem. All these factors have developed scarcity of food all over the world.

The uation has become more adverse in poorer and developing countries. Out of 70 billion of total rld population, about 10 billion have been suffering from malnutrition and partial starvation. A millions are dying out of starvation or diseases caused by malnutrition. People of Africa, Latin serica and Asia are the main victims of food scarcity.

Impact of food scarcity :

Food scarcity is not only taking lives due to starvation and malnutrition, besides these, it also has some other impacts on human life and environment. To increase crop production, a land is cultivated two or three times in a year. In developing countries, chemical fertilizers are applied indiscriminately to increase yield. By this practice, the natural fertility of soil is lost, also the soil pH changes.

Forest lands are encroached upon by farming. This practice results in deforestation which is followed by soil erosion and flood. Random use of pesticides in the crop fields cause soil and water pollution that may result into many incurable diseases. Irrigation of crop fields by suction of underground water is reducing the underground water reserve and causing arsenic pollution.

Question 9.
Refer to a specific incident related to world food probiem. Give examples of different alternative food sources. 2+3
Answer:
Special incident related to world food problem :
Between July 2011 and mid 2012, a severe drought affected the entire East Africa region. The drought caused a severe food crisis across Somalia, Ethiopia and Kenya that threatened the liveliheed of 9.5. million people. The United Nations officially declared famine in two regions in the southern part of Somalia.

Alternative food sources :
To meet the additional demand for food, scientists and nutrition experts have found dietary potentials in some plant products, other than the common food materials.

1. Moringa oleifera has incredible nutritional value. Many edible parts, like fruits, seeds, leaves, flowers are rich in protein, iron, Vit. A and Vit. C. It also has great medicinal importance.
2. Yam bean contains enough carbohydrates, dietary fibres and Vit. C. it can be consumed raw as salad or cooked, baked and even fried. Yam bean seeds contains oil.
3. Sago is a carbohydrate rich matter, extracted from the stem of some palm trees. The granular shape is obtained by mechanical processing. It is tasty and has good nutritive value.
4. Gum arabic is used to prepare chewing gum. Gaur gum is applied as thickener in confectionary formulations.
5. Green gaur beans are eaten as vegetable and are used as fodder.

Question 10.
Discuss the causes of world food problem.
Answer:
Causes of world food problem :
The main causes of world food problem are-
1. Increase in price of food: For the last three decades, the price of food has been it globally. Due to high price rise, people of developing countries are facing serious prob

2. Old method of farming: The practice of conventional farming like monoculture (without crop rotation), using of low yielding seed varieties, using of chemical fertilizers, farming without soil testing and lack of co-ordination between farmers and marketing sectors are the main reasons of food problems in developing countries.

3 Climatic change and natural calamities: Scarcity of rainfall or excessive rain may affect the production rate. Natural calamities, like flood or drought, also reduces the productivity of food throughout the world.

4. Erosion of soil and soil pollution: Soil erosion reduces the land, available for cultivation. Extensive use of chemical fertilizer reduces soil fertility and productivity. This is another cause of food problem.

5. Population explosion: On an average, 80 million people are born every year. But yearly production of food does not always reach that level to feed those new mouths. Therefore, increase in total number of population also increase food scarcity.

Question 11.
Classify the resources of energy on the basis of use. Mention the importance of conservation of energy resources. 3+2
Answer:
Classification of energy resources :
On the basis of use, energy resources can be classified into two types, which are mentioned below.
1. Conventional energy resources: Conventional energy resources are those which have been traditionally used for many years. These resources are also widely used at present and likely to be depleted. Example-Coal, Petroleum, Natural gas, Hydel power.

2. Non-conventional energy resources: Non-conventional energy resources are alternate energy resources to the conventional energy resources which are being considered to be used on large scale. The conventional energy resources are likely to be depleted in about 50-60 years and non-conventional energy resources should be fully developed by then to meet the energy requirement. Example-Solar energy, Wind energy, Geothermal energy, Tidal power, Biogas etc.

Importance of conservation of energy resources :

1. Energy is of the basic needs of life, therefore resources of energy must be conserved.
2. The conventional resources of energy, especially coal and petroleum are non-renewable, therefore they must be conserved for future generation.

Question 12.
Mention three basic steps towards conservation of energy resources. Mention the different uses of energy. 2+3
Answer:
Basic steps towards conservation of energy resources –
Steps towards conservation of energy resources are as follows-

• Thermal power generation is to be regulated to conserve coal.
• Conventional sources of energy are to be replaced by nonconventional energy sources as far as practiceable.
• Misuse and wastage of energy resources must be cut down substancially.

Different uses of energy :
Energy requirements in different purposes are –
1. Domestic use: In rural areas, wood, coal and kerosene oil are utilized for heating and lighting purpose. In urban areas, energy is used for cooking, lighting rooms, heating, cooling, running electronic gadgets, washing machines, dishwasher, vacuum cleaners, water suction pumps etc.

2. Commercial use: In commercial buildings, such as shops, malls, hotels and restaurants, energy is used for lighting, cooling, heating and running utility gadgets.

3. Industrial use: In industries, coal, oil and natural gas are used for heating, burning and melting purposes. Lighting and running machines depend upon electrical energy.

4. Use in transport: Most of the vehicles, ranging from motor-bikes to aeroplanes, motor-boats to huge ships, run by petroleum based fuels.
Nowadays atomic energy is used to run huge submarines and aircraft carriers.

Question 13.
Mention the methods of energy conservation in daily life.
Answer:
Method of energy conservation in daily life –
Energy can be consumed to a large extent in daily life by the following measures –
1. Lighting: Walls to be painted in lighter shade. Lamps should be kept dust free. Incandescent bulbs needs to be replaced with CFL to LED lamps. Electronic chokes be used instead of copper chokes.

2 Fans: Fans to be switched off before leaving room. Electronic regulators be fitted.

3. Electric iron: Ironing is to be done at right temperature. Sprayer is to be used for moistening.

4. Kitchen appliances: Grinders should be used for wet grinding. Machines are not to be run in over or under-load condition. Door of micro-oven is not to be opened frequently to check food. Flat bottom pans are to be used for induction oven.

5. Gas oven: Cooking should be done in regulated flame. Pressure cookers are to be used as much as possible. Pans to be kept covered while cooking. Before cooking items to be allowed to reach room temperature after taking out of refrigerator.

6 Water heater: Solar water heaters to be used replacing electric water heater

7. Electronic devices: Before leaving room even for short intervals, TV and audio systems should be turned off.

8. Computers: Computer monitor to be turned off during long time downloading.

9. Refrigerator: Star-rated energy saver models are to be used. Frequent opening of the door should be avoided. Door padding should be air-tight.

10. Washing machines: Washing machines should be run in full load condition at optimum water level. Perfect water and detergent quantity should be maintained.

11. Air conditioners: Energy saving star-rated equipments are to be installed and to be selected according to cooling capacity and room size. Outdoor unit is to be fitted in shady place. Filters be cleaned regulatory. Doors and windows of the room are to be sealed perfectly.

Detailed explanations in West Bengal Board Class 9 Life Science Book Solutions Chapter 1.3D Classification of Kingdom Animalia offer valuable context and analysis.

WBBSE Class 9 Science Chapter 1.3D Question Answer – Classification of Kingdom Animalia

Very Short Questions and Answers : (1 mark for each question)

Question 1.
In tripioblastic animals, which germinal layer is present in between ectoderm and endoderm?
Answer:
In triploblastic animals, mesoderm layer is present in between ectoderm and endoderm.

Question 2.
Name a phylum in which mesenchyme is present in between ectoderm and endoderm?
Answer:
In phylum Porifera, mesenchyme is present between ectoderm and endoderm.

Question 3.
Animals of which phylum possess pseudocoelom?
Answer:
Animals of phylum Nematoda possess pseudocoelom.

Question 4.
Members of which phylum use setae or parapodia for locomotion?
Answer:
Animals of phylum Annelida use setae or parapodia for locomotion.

Question 5.
In which group of animals do you find both external and internal segmentation?
Answer:
Animals under phylum Annelida have both external and internal segmentation.

Question 6.
What is paragastric cavity?
Answer:
The cavity, present inside the body of poriferans, is called paragastric cavity.

Question 7.
What is coelenteron?
Answer:
The central tubular gastrovascular body cavity present in Cnidarians is called coelenteron.

Question 8.
What is coelom?
Answer:
Coelom is the fluid-filled cavity inside animal body surrounded by mesodermal lining.

Question 9.
What is haemocoel?
Answer:
Haemocoel is the blood-filled coelomic body cavity, found in arthropods and molluscs.

Question 10.
What is pseudocoeiom?
Answer:
Pseudocoelom is a body cavity, typically seen in nematodes, which is not surrounded by mesodermal lining.

Question 11.
What are setae?
Answer:
Setae are minute bristle-like structures, which earthworms and some other annelids use for locomotion.

Question 12.
What are parapodia?
Answer:
Parapodia are unjointed, lobe-like, paired locomotory organs of annelids, that project laterally from the body segments.

Question 13.
What are comb plates?
Answer:
Comb plates are eight equidistant cilliary plates, present along the meridional line of the body of the members of Ctenophora to help in locomotion.

Question 14.
Members of which phylum is popularly called ‘comb jelly’?
Answer:
Members of phylum Ctenophora are popularly known as ‘comb jelly’.

Question .
Animals under which phylum possess cnidoblast cells?
Answer:
Animals under phylum Cnidaria possess cnidoblast cells.

Question 16.
Members of which phylum have unsegmented body covered with thick cuticle?
Answer:
Members of phylum Nematoda have unsegmented body, covered with thick cuticle.

Question 17.
Members of which phylum have segmented body covered with thick and rigid cuticle?
Answer:
Members of phylum Arthropoda have segmented body, covered with thick and rigid cuticle.

Question 18.
Members of which phylum have metamerically segmented body covered with elastic cuticle?
Answer:
Members of phylum Annelida have metamerically segmented body covered with elastic cuticle.

Question 19.
What is metameric segmentation?
Answer: The repetition of organs and tissues at intervals along the length of the body of an animal, thus dividing the body into a linear series of similar parts or segments, is called metameric segmentation.

Question 20.
Name two phyla whose members show metameric segmentation?
Answer:
Metameric segmentation is seen in the members of Annelida and Arthropoda.

Question 21.
Which group of animals use malpighian tubules for excretion?
Answer:
Members of the class Insecta, under phylum Arthropoda, use malpighian tubules as excretory organs.

Question 22.
Which group of animals use coxal gland for excretion?
Answer:
Scorpions, under class Arachnida of phylum Arthropoda, use coxal gland for excretion.

Question 23.
Which group of animals perform excretion by green gland?
Answer:
Prawns, under class Crustacea of phylum Arthropoda, perform excretion by green gland.

Question 24.
Which group of animals perform respiration by ctenidia?
Answer:
Aquatic snails and mussels, under phylum Mollusca, perform respiration by ctenidia.

Question 25.
Animals under which phylum possess canal system in their body?
Answer:
Animals under phylum Porifera possess canal system in their body.

Question 26.
Animals under which phylum perform locomotion by tube feet?
Answer:
Animals under phylum Echinodermata perform locomotion by tube feet.

Question 27.
Animals under which two classes possess four-chambered heart?
Answer:
Animals under class Aves and Mammalia, possess four-chambered heart.

Question 28.
Which group of vertebrates do not possess teeth?
Answer:
Birds do not possess teeth.

Short Questions and Answers : (2 marks for each question)

Question 1.
What are diploblastic animals?
Answer:
Those animals, whose body consists of two germinal layers, i.e. ectoderm and endoderm, are known as diploblastic animals. Example – Hydra etc.

Question 2.
What are triploblastic animals?
Answer:
Those animals, whose body consists of three germinal layers, i.e. ectoderm, mesoderm and endoderm, are known as triploblastic animals. Example -Tapeworms, earthworms etc.

Question 3.
What is meant by bilaterally symmetrical animals?
Answer:
The animals, which when divided once along the central axis gives two similar halves, are called bilaterally symmetrical animals. Example – Cockroach, human etc

Question 4.
What is meant by radially symmetrical animals?
Answer:
The animals, which when divided in any plane along the central axis gives rise to unlimited number of identical halves, are called radially symmetrical animals. Example – Starfish etc.

Question 5.
What is meant by asymmetrical animals?
Answer:
The animals, which when divided along any plane of the body, does not give rise to equal halves, are called asymmetrical animals. Example-Amoeba, molluscs etc.

Question 6.
What is spongocoel?
Answer:
The single, large central body cavity of the poriferan is called spongocoel. Water enters this cavity through several tiny pores called ostia and exits through a large opening called osculum.

Question 7.
What is meant by canal system?
Answer:
The animals under phylum Porifera have numerous pores all over the body. Through these pores water enters into the body and flows in all direction through a network of fine canals. This is called canal system.

Question 8.
What are ostia and osculum?
Answer:
Ostia: The animals under phylum Porifera possess numerous small pores all over their body which allow water to enter the body. These tiny pores are called ostia.

Osculum: The body cavity of the poriferans opens outside through a narrow circular opening, situated at the free end of their body. This opening is called osculum.

Question 9.
What is mesenchyme?
Answer:
Mesenchyme or mesohyl is a jelly-like layer with a few scattered cells and collagen fibres, present in between the two layers of cells of the body of the members of phylum Porifera and Ctenophora.

Question 10.
What is mesoglea?
Answer:
Mesoglea is a completely non-cellular jellylike layer, typically seen in between ectoderm and endoderm layer of the animals under phylum Cnidaria.

Question 11.
What is cnidoblast cell?
Answer:
Cnidoblast cell is a typical explosive epidermal cell, present in numbers on the tentacles of cnidarians. These cells carry huge secretory organelle, called nematocyst, which injects strong neurotoxin into the body of the preys and attackers.

Question 12.
What is nematocyst?
Answer:
Nematocyst is a typical stinging cell, present in the cnidoblast of cnidarians. This is a vesicle with a hairlike sensory process ejecting, called cnidocil, which discharges strong paralysing material to the preys and attackers.

Question 13.
What is gastrovascular cavity or coelenteron?
Answer:
The central tubular body cavity of cnidarian is called gastro vascular cavity or coelenteron. This cavity functions as both oral cavity as well as digestive cavity. It plays an important role in the digestion process of cnidarians.

Question 14.
What are collobiast cells or lasso cells?
Answer:
Colloblast cells or lasso cells are a kind of adhesive cells, present typically on the tentacles of the members of phylum Ctenophora. These cells are used to capture prey during predation.

Question 15.
What is metamere or somite?
Answer:
The body of annelids are transversely divisible into a series of several similar ring-like segments. These are called somites or metameres.

Question 16.
What is cephalothorax?
Answer:
The body of the members of phylum Arthropoda is segmented into head, thorax and abdomen. But certain crustaceans, such as prawn, crab, lobster etc. have their head fused with thorax. This typical structure is called cephalothorax.

Question 17.
What is mantle?
Answer:
The soft visceral organs of all molluscs remain covered with a typical muscular membrane. This is called mantle. In shelled molluscs, mantle remains just beneath the shell and secrete calcium carbonate and conchiolin, that creates the shell.

Question 18.
What is ambulacrum?
Answer:
Ambulacrum is one of the numerous equidistant radial bands, present medially along the oral side of an arm of echinoderms. It is an elongated area along which numerous tube feet protrude in two rows.

Question 19.
What is water-vascular system?
Answer:
In echinoderms, one ring canal and five sets of radial canals with their branches, connect with numerous tube feet and constitute a well organised vascular system. Through this, water flows within their body and helps them in locomotion, respiration and food and waste transportation. This typical circulatory system is known as water-vascular system.

Question 20.
What is notochord?
Answer:
Notochord is a rod-shaped, cartilaginous, axial supporting structure, typically possessed by all embryonic and some adult chordates. It forms the primitive axis of embryo among the chordates. It is made up of cells derived from mesoderm.

Question 21.
What is nerve cord?
Answer:
Nerve cord is a tubular structure, situated longitudinally along the dorsal side of the notochord in chordates. This is ectodermal in origin and is composed of nerve cells. In vertebrates, the anterior bulbous portion of nerve cord forms the brain and the posterior tubular portion becomes the spinal cord.

Question 22.
What are pharyngeal gill slits?
Answer:
Pharyngeal gill slits are paired pores, situated laterally at two opposite sides of the pharynx of all embryonic and several adult chordates. These pores are equipped with well-vascularised structures (gills), which act as respiratory organs that help to breath in amniotic fluid.

Question 23.
What are Protozoa?
Answer:
All the unicellular, eukaryotic, microscopic organisms, which belong to the kingdom Protista, are called Protozoa. Example-Amoeba, Paramoecium etc.

Question 24.
What are Parazoa?
Answer:
The primitive type of multicellular organisms under kingdom Animalia, having no specific tissues, organs or organ systems, are called Parazoa. Example-Sponges.

Question 25.
What are Metazoa?
Answer:
All the multicellular organisms under kingdom Animalia, having well-differentiated tissues, organs and organ systems, in order to carry out various physiological activities, are called Metazoa. Example-Sea anemones, earthworms, fishes etc.

Question 26.
What is Porifera?
Answer:
The phylum under kingdom Animalia, whose members possess body, composed of two layers and numerous pores and complex canal system, but lack true tissues, is called Porifera. ExampleScypha, Sycon, Spongilla etc.

Question 27.
What is Cnidaria?
Answer:
The phylum under kingdom Animalia, whose members are the diploblastic animals having a central body cavity with a single opening and tentacles equipped with stinging cnidoblast cells, is called Cnidaria. Example-Aurelia aurita (jellyfish), Metridium sp. (sea anemone) etc.

Question 28.
What is Ctenophora?
Answer:
The phylum under kingdom Animalia, whose members are marine, diploblastic, acoelomate, bisexual, having biradially symmetrical body and eight equidistant comb-like meridional cilliary plates along the body surface, is called Ctenophora. Example-Hormiphora, Beroe etc.

Question 29.
What is Platyhelminthes?
Answer:
The phylum under kingdom Animalia, whose members are triploblastic, bilaterally symmetrical animals with acoelomate, dorsiventrally flat body is called Platyhelminthes. Example-Planaria (flatworm), Taenia (tapeworm), Fasciola (liver fluke) etc.

Question 30.
What is Nematoda or Nemathelminthes or Ascheiminthes?
Answer:
The phylum under kingdom Animalia, whose members are triploblastic, with unsegmented, tubular, pseudocoelomic and bilaterally symmetrical body is called Nematoda or Nemathelminthes or Aschelminthes. ExampleAscaris (round worm), Wuchereria (filarial worm) etc.

Question 31.
What is Annelida?
Answer:
The phylum under kingdom Animalia, whose members are triploblastic, having true coelome and body transversely segmented into a number of ring-shaped somites or metameres, is called Annelida. Example-Pheretima (earthworm), Hirudinaria (leech) etc.

Question 32.
What is Arthropoda?
Answer:
The phylum under kingdom Animalia, whose members are triploblastic, having bilaterally symmetrical body, covered with chitinous exoskeleton and paired jointed appendages, is called Arthropoda. Example-Palaemon (prawn), Periplaneta (cockroach) etc.

Question 33.
What is Mollusca?
Answer:
The phylum under kingdom Animalia, whose members are triploblastic, coelomate, asymmetric or bilaterally symmetrical, having soft, unsegmented body, with visceral organs covered by a typical muscular membrane named mantle and the entire body covered with hard calcareous shell, is called Mollusca. Example-Pila (apple snail), Achatina (garden snail) etc.

Question 34.
What is Echinodermata?
Answer:
The phylum under kingdom Animalia, whose members are triploblastic, coelomate, pentaradially symmetrical, with numerous spines or ossicles on skin and unique water-vascular system in the body, is called Echinodermata. Example-Asterias (starfish), Cucumaria (sea cucumber) etc.

Question 35.
What is Chordata? Give example.
Answer:
The phylum under kingdom Animalia, whose members are diploblastic, coelomate, bilaterally symmetrical, which, at any phase of their life cycle possess notochord, dorsal tubular nerve cord, pharyngeal gill-slits and a post anal tail, is called Chordata. Example-Shark, toad, lizards, birds, mammals, etc.

Question 36.
How many sub-phyla are there under phylum Chordata? Name them.
Answer:
There are three sub-phyla under phylum Chordata. They are-Urochordata, Cephalochordata and Vertebrata.

Question 37.
What is Protochordata?
Answer:
The animals under phylum Chordata, in which notochord is not replaced by vertebral column, are called protochordates. The group which consists of these animals, is called Protochordata. Members of the sub-phyla Urochordata and Cephalochordata belong to this group.

Question 38.
What is Hemichordata? Give example.
Answer:
The phylum under kingdom Animalia, whose members are triploblastic, coelomate, with worm-like body divisible into proboscis, collar and trunk, having a dorsal tubular nerve cord and a number of paired pharyngeal gill slits, is called Hemichordata. ExampleBalanoglossus, Saccoglossus etc.

Question 39.
What is Urochordata or Tunicata?
Answer:
The sub-phylum under phylum chordata, the body of whose members is covered with a thin and transparent coat or tunic and their larvae possess the notochord restricted at the tail region, is called Urochordata or Tunicata. ExampleAscidia, Doliolum, Salpa etc.

Question 40
What is Cephalochordata or Acrania?
Answer:
The sub-phylum under phylum Chordata whose members are free-swimming, marine, having small lanceolate body and a well developed notochord extending from head to tail, is called Cephalochordata or Acrania. ExampleBranchiostoma, Asymmetron etc.

Question 41.
What is Vertebrata?
Answer:
The members of phylum Chordata, which possess a cranium, vertebral column and a welldeveloped endoskeleton, are called vertebrates and the sub-phylum is called Vertebrata. Example-Fishes, toads, dogs etc.

Question 42.
What is Agnatha?
Answer:
The vertebrates, which have a mouth without jaws, belong to a superclass called Agnatha. Example-Petromyzon (lamprey) etc.

Question 43.
What is Cyclostomata?
Answer:
The vertebrates, which have a round, jawless suctorial mouth, cartilaginous endoskeleton and a single nostril, belong to the class Cyclostomata. Example-Myxine (hagfish).

Question 44.
What is Gnathostomata?
Answer:
The vertebrates, whose mouth is guarded by a pair of jaws, having bony endoskeleton and two external nostrils, belong to a super-class called Gnathostomata. Example-Sharks, toads, mammals etc.

Question 45.
What is Chondrichthyes or Elasmobranchii?
Answer:
The class under kingdom Animalia, which includes jawed vertebrates, having cartilaginous endoskeleton, placoid scales on skin, mouth at the ventral side of the head and heterocercal or unevenly lobbed tail fin, is called Chondrichthyes or Elasmobranchii. Example-Scoliodon (shark), Dasyatis (stingray).

Question 46
What is Osteichthyes or Teleostomi?
Answer:
Osteichthyes or Teleostomi is a class under kingdom Animalia, which includes jawed vertebrates, having bony endoskeleton, paired gills covered with operculum, anteriorly placed mouth and homocercal or evenly lobbed tail fin. Example-Labeo rohita (rohu fish), Catla catla (catla fish) etc.

Question 47.
What is Amphibia?
Answer:
Amphibia is a class under kingdom Animalia, which includes cold-blooded vertebrates, with bony endoskeleton, which perform reproduction, spend larval life in aquatic environment but on maturity spend most of their life on land, have their body covered with naked, moist glandular skin and have a three-chambered heart. Example-Duttaphrynus (toad), Rana (frog) etc.

Question 48.
What is Reptilia?
Answer:
Reptilia is a class under kingdom Animalia, which includes cold-blooded vertebrates, whose body is covered with dry epidermal scales or scutes, have pentadactyl limbs with clawed digits (exception snakes) and perform respiration with the help of lungs. Example-Calotes (garden lizard), Naja (cobra) etc.

Question 49.
What is Aves?
Answer:
Aves is a class under kingdom Animalia, which includes warm-blooded vertebrates, whose body is covered with feathers, jaws modified into beaks, fore limbs modified into wings and have four-chambered heart. Example-Corvus (crow), Pavo (peacock) etc.

Question 50.
What is Mammalia?
Answer:
Mammalia is a class under kingdom Animalia, which includes warm-blooded vertebrates having body hair, a pair of pinnae at two sides of the head and the female members possess mammary glands to feed milk to their offsprings. Example-Canis (dog), Felis (cat) etc.

Question 51.
Which animals are called poikilothermic or cold-blooded animals?
Answer:
Body temperature of certain animals increases and decreases according to the rise and drop of environmental temperature. These animals are called poikilothermic or cold-blooded animals. Example-Fishes, amphibians and reptiles.

Question 52.
Which animals are called endothermic or homoeothermic or warm-blooded animals? Give examples.
Answer:
Body temperature of certain animals does not fluctuate with the change in environmental temperature. These animals are called endothermic or homoeothermic or warm blooded animals. Example-Birds and mammals.

Long Questions and Answers : (5 marks for each question)

Question 1.
Schematically represent the classification of animal kingdom with one example each.
Answer:
Schematic representation of the classification of animal kingdom.

Question 2.
Mention the identifying features of phylum Porifera. Give two examples with scientific names.
Answer:
Identifying features of phylum Porifera
The identifying features of phylum Porifera are as follows-

• Body is multicellular, without well-developed tissue system.
• Body is arranged in two layers and jelly-like mesenchyme is present in between these two layers.
• Exoskeleton is hard and rigid, made up of calcium or silicon-rich cells, called spongin fibres or spicules.
• One large aperture, called osculum is present at the upper end of the body. There are numerous tiny pores, called ostia, spreaded all over their body.
• Water flows continuously in the body through pores, interconnected canals and chambers.

Example with scientific names:
Two examples of the members of phylum Porifera are Neptune’s cup (Poterion neptuni) and freshwater sponge (Spongilla lacustris).

Question 3.
Mention the identifying features of phylum Cnidaria. Give two examples with scientific names.
Answer:
Identifying features of phylum Cnidaria

The identifying features of phylum Cnidaria are as follows-

• Members of this group live in water.
• They have a soft diploblastic body, made up of ectoderm and endoderm. In between these two layers, an acellular jelly-like mesoglea is present.
• Body radially or biradially symmetrical, has a gastrovascular cavity called coelenteron. This cavity has a single opening that is surrounded by tentacles.
• Typical stinging cells, called cnidoblasts, are present on the tentacles, equipped with a special stinging structure called nematocyst, which is used to capture prey and for self-defence.

Example with scientific names:
Two examples of the members of phylum Cnidaria are hydra (Hydra viritlis) and jellyfish (Aurelia aurita).

Question 4
Mention the identifying features of phylum Ctenophora. Give two examples.
Answer:
Identifying features of phylum Ctenophora

The identifying features of phylum Ctenophora are as follows-

• Body is diploblastic, made up of ectoderm and endoderm and bi-radially symmetrical. In between ectoderm and endoderm, a layer of jelly-like substance called mesenchyme is present.
• Body distinguishable into oral and aboral ends. The aboral end consists of a sensory structure, called statocyst.
• Eight quidistant longitudinal ciliary plates or comb plates are present on the body that help in locomotion.
• Typical adhesive cells, called colloblast cells or lasso cells are present in the tentacles. These colloblast cells help in capturing prey during predation.

Example of Ctenophores
Two examples of the members of phylum Ctenophora are Hormiphora plumosa and Beroe forskalii.

Question 5.
Mention the identifying features of phylum Platyhelininthes. Give two examples with scientific names.
Answer:
Identifying features of phylum Platyheiminthes

The identifying features of phylum Platyhelminthes are as follows-

• Body is dorsiventrally flat, so are called flatworms and externally covered by syncytial membrane. Their body is bilaterally symmetrical.
• Body wall is composed of three germinal layers-ectoderm, mesoderm and endoderm. Hence, they are triploblastic.
• Body cavity or coelom is absent. Body consists of a distinct head region and a prominent sucker at the mouth.
• Except reproductive system, other organ systems are not well developed. Excretion occurs by flame cells or protonephridia.
• All members of this group are hermaphrodite, i.e., bisexual.
• They may be free-living or parasitic.

Example with scientific names
Two examples of the members of phylum Platyhelminthes are tapeworm (Taenia solium) and liver fluke (Fasciola hepatica).

Question 6.
Mention the identifying features of phylum Nemathelminthes or Nematoda. Give two examples with scientific names.
Answer:
Identifying features of phylum Nemathelminthes or Nematoda

The identifying features of the phylum Nemathelminthes are as follows-

• Body is bilaterally symmetrical, long and cylindrical.
• They are triploblastic, i.e., body wall composed of three germinal layers-ectoderm, mesoderm and endoderm.
• Body is unsegmented and is covered with thick cuticle.
• A very narrow, fluid-filled body cavity or pseudocoelom is present. Organ systems are poorly developed.
• Members of this group are unisexual, i.e., with separate male and female individuals.

Example with scientific names:
Two examples of the members of phylum Nematoda are filarial worm (Wuchereria bancrofti) and hookworm (Ancylostoma duodenale).

Question 7.
Mention the identifying features of phylum Annelida. Give two examples with scientific names.
Answer:
Identifying features of phylum Annelida

The identifying features of phylum Annelida are as follows

• Body is composed of several ring-like segments called metameres or annuli. Hence, they are named annelids.
• Body is bilaterally symmetrical and triploblastic, i.e.body wall divided into ectoderm, mesoderm and endoderm.
• True body cavity or coelom is present. Organs are well differentiated.
• The annelids use setae and parapodia for locomotion.
• Each body segment bears a pair of nephridia, which act as excretory organs.

Example with scientific names
Two examples of the members of phylum Annelida are earthworm (Pheretima posthuma) and sand worm (Nereis virens).

Question 8.
Mention the identifying features of phylum Arthropoda. Give two examples with scientific names.
Answer:
Identifying features of phylum Arthropoda

The identifying features of phylum Arthropoda are as follows –

• Body is bilaterally symmetrical and externally segmented.
• The organisms have paired jointed appendages for locomotion.
• Body wall composed of ectoderm, mesoderm and endoderm, i.e., they are triploblastic.
• Body generally differentiated into head, thorax and abdomen. In some cases, head and thorax fuse together, forming cephalothorax.
• Thick and rigid exoskeleton is present, which is made up of chitin.
• Circulatory system is open, i.e., blood flows in coelomic body cavity, which is called haemocoel.

Example with scientific names
Two examples of the members of phylum Arthropoda are cockroach (Periplaneta americana), housefly (Musca domestica).

Question 9.
Mention the identifying features of phylum Mollusca. Give two examples with scientific names.
Answer:
Identifying features of phylum Mollusca

The identifying features of phylum Mollusca are as follows-

• Body is soft, bilaterally symmetrical, unsegmented and muscular.
• Body of most of the members are enclosed within a hard caicareous shell, made up of calcium carbonate.
• Visceral mass remains covered with a muscular membrane, called mantle.
• They have reduced body cavity and open circulatory system.
• Body bears kidney-like organs for excretion. They perform respiration by a single or a pair of gill-like organs present within pulmonary sac or by means of ctenidia.
• A special apparatus, called radula, is present at the base of mouth. It bears rows of chitinous teeth, which help in scrapping or cutting food.
• Creeping members of this phylum have muscular foot and swimming members have undulating membrane for lacomotion.

Example with scientific names
Two examples of the members of phylum Mollusca are garden snail (Achatina fulica) and squid (Loligo vulgaris).

Question 10.
Mention the identifying features of phylum Echinodermata. Give two examples with scientific names.
Answer:
Identifying features of phylum Echinodermata

The identifying features of phylum Echinodermata are as follows-

• Body is triploblastic, i.e., body wall made up of ectoderm, mesoderm and endoderm and body is pentaradially symmetrical.
• Body differentiated into oral and aboral surfaces.
• Body surface bears numerous spines and their endoskeleton consists of hard, calcareous ossicles, that are made up of calcium carbonate.
• Oral surface of the body has five radial ambulacra with distinct ambulacral grooves.
• They have a proper coelomic cavity and wellorganised water-vascular system that is used for circulation.
• Numerous tube feet are present on either side of the ambulacral grooves, which help in locomotion.

Example with scientific names
Two examples of the members of phylum Echinodermata are starfish (Asterias rubens), and sea cucumber (Cucumaria frondosa).

Question 11.
Mention the Identifying features of phylum Hemichordata. Give two examples.
Answer:
Identifying features of phylum Hemichordata

The identifying features of phylum Hemichordata are as follows-

• Members of this group are Balanoglossus soft bodied, coelomate, worm-like, marine animals.
• Body is divided into proboscis, collar and trunk.
• Paired pharyngeal gill slits are present in the trunk.
• They are devoid of endoskeleton and notochord.
• The nerve cord is dorsally placed, which is rod-like in most members, but hollow in few.
• A small diverticulum is present near oesophagus, called stomochord, which is a flexible hollow tube that helps to communicate with oral cavity.
• They possess an independent larval stage, named tornaria larva, at initial stage of their life cycle.

Examples of hemichordates
Two examples of hemichordates are Balanoglossus gigas and Saccoglossus sp.

Question 12.
Mention the Identifying features of phylum Chordata. Give two examples.
Answer:
Identifying features of phylum Chordata
The identifying features of phylum Chordata are as follows-

• A tubular nerve cord is present at dorsal side of the body.
• Below the dorsal tubular nerve cord, the animals possess a rod-shaped supporting structure, called notochord. It remains throughout their life or at least during embryonic stage.
• Paired pharyngeal gill slits are present throughout or, at certain period of their life cycle.
• All members have a post anal tail or at least some remains of it.
• The members under this phylum possess closed circulatory system.

Example of chordates
Two examples of chordates are Branchiostoma lanceolatum and Homo sapiens sapiens.

Question 13.
Distinguish between chordates and non-chordates.
Answer:
Differences between chordates and non-chordates

Features	Chordates	Non-chordates
1. Notochord	Present throughout or at certain stage of life cycle	Completely absent
2. Nerve cord	Tubular structure, present at the dorsal side of the body	Thread-like structure, present at the ventral side of the body
3. Vertebral column	Present in most members	Completely absent
4. Skull	Present and made up of bones and cartilages	Absent
5. Circulatory system	Closed circulatory system with arteries, veins and capillaries	Open circulatory system with arteries and veins, but capillaries are absent

Question 14.
Mention the identifying features of sub-phylum Urochordata. Give two examples.
Answer:
Identifying features of sub-phylum Urochordata

The identifying features of sub-phylum Urochordata are as follows

• Sac-like soft body of the members is covered by a membrane called tunic.
• Paired pharyngeal gill slits are present in adults. The pharyngeal region is surrounded by a membrane-bound cavity, called atrium.
• Notochord and nerve chord present during larval stage.
• Free-swimming tadpole stage is observed during the life cycle of the organisms. They undergo retrogressive metamorphosis by losing notochord and nerve cord on maturity.

Example of urochordates
Two examples of urochordates are Ascidia mentula and Doliolum denticulatum.

Question 15.
Mention the identifying features of sub-phylum Cephalochordata. Give two examples.
Answer:
Identifying features of sub-phylum Cephalochordata

The identifying features of sub-phylum Cephalochordata are as follows-

• This sub-phylum includes small fish-like animals with indistinct head. Body is bilaterally symmetrical, triploblastic and with coelomic body cavity.
• Notochord is well developed, which contracts and expands and extends from head to tail.
• Dorsal tubular nerve cord and paired pharyngeal gill slits are present.
• A typical ciliated groove, called endostyle, is present at the ventral wall of pharynx.
• Oral opening is laterally guarded by two flap-like structures, called oral hoods, with ciliated edge.

Example of cephalochordates
Two examples of cephalochordates are Branchiostoma lanceolatum and Asymmetron inferum.

Question 16
Mention the identifying features of sub-phylum Vertebrata or Craniata. Give two examples with scientific names.
Answer:
Identifying features of sub-phylum Vertebrata or Craniata
The identifying features of sub-phylum Vertebrata are as follows-

• Members of this group are bilaterally symmetrical, triploblastic and with coelomic body cavity.
• Notochord is replaced by a true vertebral column. Body possesses internal skeleton, made up of bones and cartilage.
• Brain remains protected inside cranium.
• Dorsal tubular nerve cord emerges from base of the brain and passes through the vertebral column.
• Two pairs of joint limbs present, which help in locomotion.

Example with scientific names
Two examples of the members of sub-phylum Vertebrata are rohu fish (Labeo rohita) and cat (Felis domesticus).

Question 17.
Mention the identifying features of super-class Agnatha with two examples. Mention the identifying features of super-class Gnathostomata with two examples.
Answer:
Identifying features of super-class Agnatha

The identifying features of super-class Agnatha are as follows-

• Body is elongated, with cartilaginous endoskeleton.
• Suctorial mouth is present without any jaw.
• Only a single external nostril is present.
• A number of pharyngeal gill slits are present along the two opposite sides of the body.

Example – Two examples of the members of super-class Agnatha are lamprey (Petromyzon marinus) and hagfish (Myxine glutinosa).

Identifying features of super-class Gnathostomata
The identifying features of super-class Gnathostomata are as follows-

• The mouth of the animals under this super-class is guarded by a pair of jaws.
• They have two external nostrils.
• Endoskeleton is made up of either bone or cartilage

Example- Two examples of the members of super-class Gnathostomata are shark (Scoliodon sorrakowah) and crocodile (Crocodylus porosus).

Question 18.
Mention the identifying features of class Cyclostomata. Give two examples with scientific names.
Answer:
Identifying features of class Cyclostomata

Cyclostomata is the only class under super-class Agnatha. Its characteristic features are as follows:

• The animals under this class are cold-blooded. Mouth has no jaw. Oral opening has a circular sucker, which is guarded by papillae or small tentacles.
• One medial external nostril is present.
• Body is long, cylindrical, tapering towards the tail.
• The members do not have distinct stomach or any appendages.
• Fertilisation, as well as development, both are external.
• They possess unpaired fins and do not have body scales.
• Skull and endoskeleton, both are cartilaginous.
• Heart is two-chambered, 6-14 pairs of gills present in sac.

Example with scientific names
Two examples of the members of class Cyclostomata are lamprey (Petromyzon marinus) and hagfish (Myxine glutinosa).

Question 19
Mention the identifying features of class Chondrichthyes. Give two examples with scientific names.
Answer:
Identifying features of class Chondrichthyes

The identifying features of class Chondrichthyes are as follows-

• The animals under this class Shark are cold-blooded and bilaterally symmetrical.
• Members of this group have streamlined body and cartilaginous endoskeleton.
• Body is covered with minute placoid scales.
• About 5-7 pairs of gill slits present at the lateral side of the body and are without operculum.
• Mouth present at the ventral side of the head.
• Body has paired and unpaired fins, with fin rays. Air bladder typically absent.
• They possess heterocercal tail, i.e., with two unequal lobes. Anal fins of male form claspers, which help to deposit sperms.

Example with scientific names
Two examples of the members of class Chondrichthyes are shark (Scoliodon sorrakowah) and sawfish (Anoxypristis cuspidata).

Question 20.
Mention the identifying features of class Osteichthyes. Give two examples with scientific names.
Answer:
Identifying features of class Osteichthyes

The identifying features of the class Osteichthyes are as follows

• The animals under this class are bilaterally symmetrical and are cold-blooded animals.
• They have streamlined body covered with ganoid, cycloid or ctenoid scales.
• Their endoskeleton and fin rays are made up of bones.
• Four pairs of gills present in gill chambers on either side of head. Each gill Rohu fish chamber remains covered with a bony plate, called operculum.
• Five pairs of gill arches and one pair of external gill slits present.
• They have paired or unpaired fins, with bony fin rays.
• Tail fin is homocercal with identical lobes.
• A typical swim bladder is present in the body.

Example with scientific names
Two examples of the members of class Osteichthyes are rohu fish (Labeo rohita) and catla fish (Catla catla).

Question 21.
Mention the identifying features of class Amphibia. Give two examples with scientific names.
Answer:
Identifying features of class Amphibia

The identifying features of class Amphibia are as follows-

• The animals belonging to this class are cold-blooded animals.
• Body is differentiated into head and trunk, without distinct neck.
• Body is covered with naked, moist, glandular skin without scales.
• Larvae live in water and respire with external gills. Adults are terrestrial and respire with lungs, but apart from this, skin and buccopharyngeal cavity also participate in respiration.
• Forelimbs have four and hind limbs have five digits each. The digits are without claws.
• They have three-chambered heart, with two auricles and one ventricle.

Example with scientific names
Two examples of the members of class Amphibia are toad (Duttaphrynus melanostictus) and frog (Rana tigrina).

Question 22.
Mention the identifying features of class Reptilia. Give two examples with scientific names.
Answer:
Identifying features of class Reptilia

The identifying features of class Reptilia are as follows –

• The animals under this class are cold-blooded animals.
• Body is covered with large dermal plates or dry epidermal scales, called scutes.
• They perform locomotion by crawling.
• Each of the fore and hind limbs have five clawed digits. (exception-snakes are limbless).
• Body is distinctly divisible into head, neck, trunk and tail. Cloaca is present transversely near the base of the tail.
• They generally have three chambered heart, with two auricles and a partially divided ventricle (exception – crocodile has four-chambered heart with completely divided ventricle).

Example with scientific names
Two examples of the members of class Reptilia are garden lizard (Calotes versicolor) and crocodile (Crocodylus porosus).

Question 23
Mention the identifying features of class Aves. Give two examples with scientific names.
Answer:
Identifying features of class Aves

The identifying features of the class Aves are as follows-

• The animals belonging this class are warm-blooded animals.
• Body is spindle-shaped and covered with feathers.
• Forelimbs are modified into wings.
• Their bones are hollow due to the presence of air cavities. This helps to reduce their weight and help in flying.
• Besides lungs, they have 9 air sacs, which help in flight.
• Urinary bladder, rectum and right ovary absent in order to reduce body weight.
• Teeth completely absent and jaws are modified into beaks.
• They have four-chambered heart with two auricles and two ventricles.

Example with scientific names
Two examples of the members of class Aves are crow (Corvus splendens) and pigeon (Columba livia).

Question 24
Mention the identifying features of class Mammatia. Give two examples with scientific names.
Answer:
Identifying features of class Mammalia

The identifying features of class Mammalia are as follows-

• The animals under this class are warm-blooded animals and their bodies are bilaterally symmetrical.
• Body is covered with hair. Sweat and sebaceous glands are present in the skin.
• The female members of this group have milk-producing mammary glands, for nourishing their young ones.
• A pair of external ears or pinnae is present on either side of the head.
• Respiration occurs by a pair of lungs.
• They have two pairs of limbs, used for locomotion, digging, holding or feeding.
• They are viviparous animals, i.e., give birth to young ones.
• Heart is four-chambered with two auricles and two ventricles and has left aortic arch.

Example with scientific names
Two examples of the members of class Mammalia are man (Homo sapiens sapiens) and deer (Axis axis).