Detailed explanations in West Bengal Board Class 9 Life Science Book Solutions Chapter 3.1A Plant Physiology: Photosynthesis offer valuable context and analysis.

WBBSE Class 9 Science Chapter 3.1A Question Answer – Plant Physiology: Photosynthesis

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

Question 1.
Name the scientist who coined the term ‘photosynthesis’.
Answer:
Barnes coined the term ‘photosynthesis’.

Question 2.
Name a vascular land plant, which photosynthesises through its roots.
Answer:
Stylites andicola is a vascular land plant, which photosynthesises through its roots.

Question 3.
What does NADP stand for?
Answer:
NADP stands for Nicotinamide Adenine Dinucleotide Phosphate.

Question 4.
From which of the raw materials does glucose get its oxygen during photosynthesis?
Answer:
Glucose, the end product of photosynthesis, gets its oxygen from CO₂

Question 5.
Which element is taken up by green plants from environment in the form of an oxide?
Answer:
Carbon is absorbed by green plants from the environment in the form of an oxide, namely carbon dioxide.

Question 6.
Which biocatalyst is essential for photosynthesis?
Answer:
Chlorophyll is the biocatalyst, which is essential for photosynthesis.

Question 7.
Which pigments are necessary for photosynthesis, other than chlorophyll?
Answer:
Other than chlorophyll, carotenoids are the pigments which are necessary for photosynthesis.

Question 8.
Name two members under kingdom Protista, which are capable of synthesising their own food by photosynthesis.
Answer:
Euglena sp. and Chrysamoeba sp. are the two members under kingdom Protista, which are capable of synthesising their own food by photosynthesis.

Question 9.
Name an enzyme, necessary for the assimilation of carbon during the lightindependent phase of photosynthesis.
Answer:
The enzyme RuBisCO is necessary for the assimilation of carbon during the lightindependent phase of photosynthesis.

Question 10.
What is the full form of the enzyme RuBisCO?
Answer:
The full form of RuBisCO is Ribulose Bisphosphate carboxylase/oxygenase.

Question 11.
Which of the raw materials of photosynthesis is oxidised during the process?
Answer:
Water molecule is oxidised during the process of photosynthesis.

Question 12.
Which of the raw materials of photosynthesis is reduced during the process?
Answer:
Carbon dioxide is reduced during photosynthesis.

Question 13.
In case of terrestrial plants, which process reduces the content of CO₂ and increases the content of O₂ in the atmosphere?
Answer:
In case of terrestrial plants, the process of photosynthesis reduces the content of CO₂ and increases the content of O₂ in the atmosphere.

Question 14.
Where do plants generally store their food?
Answer:
Plants generally store their food in roots, stems and fruits.

Question 15.
What are the end products of photosynthesis?
Answer:
Glucose, oxygen and water are the end products of photosynthesis.

Question 16.
Name the following reaction:
Answer:
This reaction is named as photolysis of water.

Question 17.
Name the following reaction:
Answer:
This reaction is called photophosphorylation.

Question 18.
Who discovered that oxygen, evolved during photosynthesis, comes from water?
Answer:
British scientist Robin Hill discovered that oxygen, evolved during photosynthesis, comes from water.

Question 19.
Who discovered the reaction path of carbon assimilation?
Answer:
Scientist Blackman discovered the reaction path of carbon assimilation.

Question 20.
Who discovered the reaction path of glucose synthesis and regeneration of RuBP from PGA?
Answer:
Scientist Melvin Calvin and his co-workers discovered the cyclic reaction path of glucose synthesis and regeneration of RuBP from PGA.

Question 21.
How many phosphoglyceraldehyde (PGAld) molecules are required to produce a glucose molecule?
Answer:
Two phosphoglyceraldehyde (PGAld) molecules are required to produce one molecule of glucose.

Question 22.
Which co-enzyme carries hydrogen for the reduction of PGA?
Answer:
NADP carries hydrogen for the reduction of PGA.

Question 23.
Which compound supplies chemical energy for the reduction of PGA?
Answer:
Adenosine triphosphate (ATP) supplies chemical energy for the reduction of PGA.

Question 24.
Out of 12 PGAld molecules, how many take part in the synthesis of RuBP in Calvin cycle?
Answer:
Out of 12 PG.Ald molecules, 10 molecules take part in the synthesis of RuBP in Calvin cycle.

Question 25.
Which are the end products of light-dependent phase of photosynthesis?
Answer:
Oxygen, ATP and NADPH+H⁺ are the end products of light-dependent phase of photosynthesis.

Question 26.
Which of the end products of light-dependent phase take part in the reactions of light-independent phase of photosynthesis?
Answer:
ATP and NADPH+H⁺ are the end products of light-dependent phase, which take part in the reactions of light-independent phase of photosynthesis.

Question 27.
Which reactant of light-independent phase of photosynthesis is received from the environment?
Answer:
CO₂ is the only reactant of the light-independent phase of photosynthesis which is received from the environment.

Question 28.
Which are the essential components, necessary for light-independent reactions of photosynthesis?
Answer:
CO₂, ATP, NADPH₂, and RuBP are the essential components, which are necessary for the light independent reactions of photosynthesis.

Question 29.
Which instrument is used to measure the absorption spectrum of chlorophyll?
Answer:
The absorption spectrum of chlorophyll is measured with the help of spectrophotometer.

Question 30.
Due to excessive heat from the sun, the process of photosynthesis stops. What is this condition called?
Answer:
The condition, in which the process of photosynthesis stops due to excessive heat from the sun, is called solarisation.

Question 31.
Under what temperature does photosynthesis occur at its best?
Answer:
Photosynthesis occurs at its best at an optimum temperature ranging between 25°C – 35°C

Question 32.
Name a bacteria which can prepare its own food without performing photosynthesis.
Answer:
Thiobacillus sp, is a bacteria which can prepare its own food without performing photosynthesis.

Question 33.
In green plants, what percentage of the total stored water is used during photosynthesis?
Answer:
During photosynthesis, only 1% of the total stored water is used up by green plants.

Question 34.
Name the co-pigment present in green plants which helps in photosynthesis.
Answer:
In green plants, carotenoids act as co-pigment, which help in photosynthesis.

Question 35.
What is the absorption spectrum of carotenoid?
Answer:
Absorption spectrum of carotenoid is blue-green.

Question 36.
Name two carotenoids.
Answer:
Carotene and xanthophyll are two carotenoids.

Question 37.
Why photosynthesis does not occur in animal cells?
Answer:
Photosynthesis does not occur in animal cells because they lack chloroplast and hence the photosynthetic pigment chlorophyll.

Question 38.
Which compound is both a raw material and a by-product, in the process of photosynthesis?
Answer:
Water is both a raw material as well as a byproduct, in the process of photosynthesis.

Question 39.
How do completely submerged aquatic plants absorb necessary CO₂ for photosynthesis?
Answer:
Completely submerged aquatic plants absorb necessary CO₂ through their entire body surface by the process of diffusion.

Question 40.
Give an example of a natural and an artificial Hill reagent?
Answer:
An example of natural Hill reagent is NADP, and an example of artificial Hill reagent is potassium ferric oxalate.

Question 41.
What are the two types of photophosphorylation?
Answer:
The two types of photophosphorylation are-

• cyclic photophosphorylation and
• non-cyclic photophosphorylation.

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

Question 1.
Define photosynthesis.
Answer:
Photosynthesis is a photochemical process in which green plants and certain chlorophyll containing organisms utilise water and carbon dioxide as raw materials to synthesise monosaccharide (glucose) in their body by entrapping light energy (especially sunlight) within it and releasing oxygen as a by-product in the environment.

Question 2.
Mention the components, necessary for photosynthesis.
Answer:
The materials required for photosynthesis are as follows-

• Raw material- Water and carbon dioxide,
• Pigments – Chlorophyll and carotenoids (carotene and xanthophyll),
• Energy- Light (sunlight or bright artificial light).

Question 3.
Where does photosynthesis occur?
Answer:
Photosynthesis occurs in the chloroplast-containing parenchyma (chlorenchyma) tissues known as mesophyll tissue of higher green plants. These tissues are distributed in leaves and all other green parts of the plants, like stems (in herbs), sepals of flowers, petals (water lily and custard apple flower), bracts (vasak plant), stipule (pea plant), root (orchid, Tinospora) etc.

Question 4.
How do plants absorb water for photosynthesis?
Answer:
Terrestrial plants absorb water from the soil with the help of their roots. Aquatic plants absorb water from the surrounding water medium through their body surface by the process of simple diffusion. Epiphytes (plants growing on other plants) like orchids, have aerial roots, called velamen, with thick hygroscopic outer coating, which absorb rain water and moisture from air to fulfill the plant’s need of water.

Question 5.
How do plants absorb CO₂ for photosynthesis?
Answer:
All terrestrial plants absorb CO₂ from the atmosphere through stomata of the leaves. Aquatic plants absorb dissolved CO₂ from surrounding water by simple diffusion through body surface. Partially submerged plants absorb CO₂ through stomata of the aerial portion of their body and the submerged portion get it by diffusion from the surrounding water medium.

Question 6.
What do photosynthetic pigments in plants do?
Answer:
In plants, there are two types of photosynthetic pigments, namely, chlorophyll and carotenoids. Chlorophyll helps in the dissociation of water and formation of energy packed ATP molecules. Carotenoids (carotene and xanthophyll) trap light energy and transfer it to chlorophylls for further reaction.

Question 7.
What is meant by absorption spectrum of photosynthesis?
Answer:
The specific wavelength of visual spectrum, which is absorbed by certain plant pigments and used in photosynthesis, is called absorption spectrum of that particular pigment.

Question 8.
What is meant by action spectrum of chlorophyll?
Answer:
Out of the seven colours of the visible spectrum of light, chlorophyll molecules strongly absorb red (650-760nm) and blue (430-470nm) light which is most effective for photosynthesis. Therefore, this region of the visible spectrum denotes the action spectrum of chlorophyll.

Question 9.
Mention the events occurring during the light-dependent phase of photosynthesis.
Answer:
Five different events occur during the light dependent phase of photosynthesis. These are–

• activation of chlorophyll,
• ionisation of water (photolysis of water),
• reduction of NADP⁺
• production of oxygen and
• photosynthetic phosphorylation.

Question 10.
What is meant by activation of chlorophyll?
Answer:
Light from the sun comes to earth in the form of energy-rich particles, called photons. When photons hit a chlorophyll molecule, it gets excited and releases an energised electron. This event is known as activation of chlorophyll.

Question 11.
What is meant by photolysis or ionisation of water?
Answer:
Being hit by photons, chlorophyl molecules get excited and dissociates water molecules into protons H⁺ and hydroxyl ions OH^–. This lightdependent dissociation of water molecule is called photolysis of water. This reaction is popularly known as Hill reaction.

Question 12.
What is meant by reduction of NADP⁺ ?
Answer:
NADP⁺ is a proton acceptor, which is present in chloroplast. During light-dependent phase of photosynthesis, proton (H⁺) is produced during photolysis of water, electron (e^–) is released from an excited chlorophyll molecule and NADP⁺, present in the photosynthetic cells, react to produce NADPH+H⁺. This reaction step is known as reduction of NADP⁺.
\(\mathrm{NADP}^{+}+2 \mathrm{H}^{+}+2 \mathrm{e}^{-} \longrightarrow \mathrm{NADPH}+\mathrm{H}^{+}\)

Question 13.
How is O₂ produced during photosynthesis?
Answer:
During photolysis of water, protons (H⁺) and hydroxyl ions (H^–) are produced. These hydroxyl ions then release one electron each and are transformed into hydroxyl radicals [OH]. These radicals combine to form water H₂O and oxygen O₂ molecules. Thus, O₂ is produced during light-dependent phase of photosynthesis, which is a by-product.
\(4 \mathrm{OH}^{-} \rightarrow 4[\mathrm{OH}]+4 \mathrm{e}^{-} \rightarrow 2 \mathrm{H}_2 \mathrm{O}_2 \rightarrow 2 \mathrm{H}_2 \mathrm{O}+\mathrm{O}_2 \uparrow\)

Question 14.
What is meant by photophosphorylation?
Answer:
During light-dependent phase of photosynthesis, the energised electrons released from photon hit chlorophylls, help to combine adenosine diphosphate (ADP) and inorganic phosphate (IP) to produce an energy-rich compound, adenosine triphosphate (ATP). This reaction is known as photosynthetic phosphorylation or photophosphorylation.

Question 15.
Why is it better to designate the second phase of photosynthesis as light-independent phase rather than dark phase?
Answer:
The term dark phase apparently indicates events occurring in dark, but reactions of photosynthesis never occur in the absence of light. The second phase of photosynthesis does not need direct light but some by-products of light phase like ATP and NADPH₂, come to act here. Therefore, it is better to designate this phase as light-independent phase rather than dark phase.

Question 16.
Which reactions take place in the light-independent phase of photosynthesis?
Answer:
During light-independent phase of photosynthesis four different reactions occur. These are

• carbon assimilation,
• reduction of PGA,
• resynthesis of RuBP and
• glucose synthesis.

Question 17.
What is meant by carbon assimilation?
Answer:
The CO₂ absorbed by photosynthetic plants from the atmosphere, reacts with RuBP, a five carbon compound, present in the stroma of chloroplast, to produce phosphoglyceric acid (PGA) in the presence of an enzyme, called RuBisCO. In this reaction, carbon atom of CO₂ is assimilated within the cellular organic compounds. This reaction is known as carbon assimilation. Here, 2 molecules of PGA are produced.

Question 18
How does reduction of PGA occur in lightindependent phase of photosynthesis?
Answer:
After the production of PGA during the assimilation of carbon, two products of light-dependent phase, namely NADPH+H⁺ and ATP come into action. NADPH+H⁺ reacts with PGA and reduces it to produce phosphoglyceraldehyde (PGAld). ATP supplies the necessary chemical energy for this reaction.

Question 19.
How is glucose synthesised in the lightindependent phase of photosynthesis?
Answer:
During the light-independent phase of photosynthesis, RuBP is carboxylated to form PGA, which is reduced to phosphoglyceraldehyde (PGAld) with the help of NADPH+H⁺ and ATP. Out of the total PGAld, 5/6th part undergoes a cycle of reactions and resynthesises RuBP. And the rest 1/6th portion of the total PGAld produced, then undergoes a series of reactions to produce glucose. Two molecules of PGAld produce 1 molecule of glucose.

Question 20.
Why are green plants considered as the food producers of the environment?
Answer:
By the process of photosynthesis, inorganic materials like water and carbon dioxide combine to produce a monosaccharide, called glucose. It is the basic component of all food matters on earth. From this glucose, all other carbohydrates, proteins and lipids are produced through various metabolic processes within the plant body, which is consumed by the other organisms. This is why, green plants are considered as food producers of the environment.

Question 21.
How does solar energy enter in the living organisms?
Answer:
During photosynthesis, light energy from the sun is trapped by the chlorophyll molecules. This energy is then transformed into chemical potential energy by the formation of glucose. At the end, this energy is transferred to different consumers or heterotrophic organisms and decomposers through food chain. This is how solar energy enters in the living organisms.

Question 22.
What are the sources of the components of carbon assimilation?
Answer:
The sources of the components of carbon assimilation are-

• CO₂ – Source of CO₂ is air,
• RuBP- Source of RuBP is the mesophyll tissue of leaf,
• NADPH+H⁺ Source of NADPH+H⁺ is NADP⁺ present in chlorophyll of leaf.
  NADP+ reacts with the H⁺ ion produced by the photolysis of water to form NADPH +H⁺and
• ATP – ATP is formed by the combination of ADP and inorganic phosphate in leaf during photophosphorylation.

Question 23.
Write the differences between light-dependent and light-independent phase of photosynthesis.
Answer:

Features	Light-dependent phase.	Light-independent phase
1. Role of sunlight	Sunlight is necessary	Sunlight is not necessary
2. Site of occurrence	It takes place in the grana of chloroplast	It takes place in the stroma of chloroplast
3. Production of oxygen	Oxygen is given out during this phase	Oxygen is not given out during this phase
4. Fate of NADP	NADP+ is reduced in this process, to form NADPH + H+	NADPH+ + H+ is oxidised in this process, to form NADP+

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

Question 1.
Briefly describe the reactions of light-dependent phase of photosynthesis.
Answer:
Reactions of light-dependent phase of photosynthesis
The reactions of light-dependent phase of photosynthesis occur in the stroma of chloroplastids. Five different reactions occur in this phase, which are mentioned below.

1. Activation of chlorophyll: Light from sun reaches the earth in the form of energy-packed particles, called photons. When these photons hit the chlorophyll molecules present in the chloroplast of green leaves, they get excited and release energised electrons. This event is known as activation of chlorophyll.

2. Photolysis of water: Activated chlorophyll dissociates water molecules into protons H⁺ and hydroxyl ions H^–. This light-dependent dissociation of water molecule is called photolysis or ionisation of water.

3. Reduction of NADP+ NADP⁺ is a proton acceptor, present in the chloroplasts. Proton H⁺ produced during the photolysis of water, reacts with NADP⁺and reduces it to NADPH+H⁺. In this reaction, necessary electrons for the subsequent reactions are emitted from the excited chlorophylls.

4. Production of oxygen: Hydroxyl ions H^–, produced during the dissociation or lysis of water, release electrons and are transformed into hydroxyl radicals OH. These radicals combine to form water H₂O and oxygen O₂ molecules.

5 Photosynthetic phosphorylation: The energised electrons, released from the photon-hit chlorophylls, help to combine adenosine diphosphate (ADP) and inorganic phosphate (iP) to produce an energy-rich compound, called adenosine triphosphate (ATP). This reaction is known as photosynthetic phosphorylation or photophosphorylation.

Question 2.
‘Green plants entrap solar energy and convert it into potential energy’- explain the sentence along with a diagram.
Answer:
Entrapping of solar energy and its conversion to potential energy by green plants. The source of every form of energy on earth is sunlight. The chlorophyll present in palisade cells of green plants absorbs the photon particles of the sunlight and stores it in the form of chemical energy in ATP through various chemical reactions.

This is known as the ‘entrapping of solar energy’. Later, the chemical energy of ATP is converted into the potential energy which remains stored within the glucose which is formed by the combination of CO₂ and H₂. This is known as the ‘conversion of solar energy into potential energy’.

Question 3.
Briefly describe the steps of light-independent phase of photosynthesis along with a diagram.
Answer:
The steps of light-independent phase of photosynthesis:

The reactions of light-independent phase occurs in stroma of chloroplastids. Four different reactions occur in this phase of photosynthesis. These are as follows-

1. Carbon assimilation: Photosynthetic plants absorb CO₂ from the atmosphere. This CO₂ reacts with RuBP in the stroma of chloroplast to produce phosphoglyceric acid (PGA). The enzyme RuBisCO catalyses this reaction. In this reaction, carbon atom (C) of CO₂ is assimilated within the cellular organic compounds. This reaction is known as carbon assimilation.

2. Reduction of PGA: In this step, two products of light-dependent phase, namely NADPH+H⁺and ATP come into action. NADPH + H⁺reacts with phosphoglyceric acid and reduces it to produce phosphoglyceraldehyde (PGAld). ATP supplies the necessary chemical energy for this reaction.

3. Re-synthesis of RuBP: Out of the total PGAld produced, 5/6th part undergoes a cycle of reactions and resynthesises RuBP. This reaction cycle is named Calvin cycle. In this cycle, several intermediate compounds are produced in subsequent steps.

4. Glucose synthesis: Out of the total PGAld produced, 1/6th part takes part in the synthesis of glucose. Within the stroma of chloroplasts, PGAld molecules undergo a series of reactions to synthesise glucose.

Question 4.
Write the significance of light-dependent phase of photosynthesis. What is the significance of light-independent phase of photosynthesis?
Answer:
Significance of light-dependent phase of photosynthesis:

The significance of light-dependent phase of photosynthesis are as follows-

• During photophosphorylation of the light-dependent phase, solar energy is converted into chemical energy and is stored as ATP.
• ATP, produced during photophosphorylation and NADPH₂, produced during reduction of NADP⁺, in the light-dependent phase, help in the reduction of PGA to PGAld, later in the light-independent phase.
• During the photolysis of water, it gets dissociated to liberate oxygen. This oxygen helps in respiration of all living organisms present in the environment.

Significance of light-independent phase of photosynthesis
The significance of light-independent phase of photosynthesis are as follows –

• Solar energy gets stored in glucose as potential energy. This energy helps the living world, either directly, or indirectly, to perform all metabolic functions.
• The CO₂ released into the environment by all organisms during respiration, is taken up by plants during the light-independent phase. As a result, the balance of CO₂ and O₂ is maintained in the environment.
• During this phase, assimilation of carbon takes place and carbohydrate, in the form of glucose, is produced as an end product. This glucose, either actively, or passively, forms the source of food for all living organisms.

Question 5
What are the significance of photosynthesis?
Answer:
Significance of photosynthesis
The significance of photosynthesis are mentioned below.

1. Trapping and transformation of solar energy: Light energy from the sun is trapped by chlorophyll and transformed into chemical potential energy by the synthesis of glucose. This energy is then passed on from the plants to the consumers through food chain.

2. Production of food: By photosynthesis, inorganic materials like water and CO₂ combine to produce glucose, which is the basic component of all food matters on earth. Not only plants but other animals also obtain this food, either directly or indirectly, to survive.

3. Maintenance of O₂ and CO₂ balance in the environment: During respiration, all living organisms release CO₂ and absorb O₂ .On the other hand, green plants release O₂ and absorb CO₂ during photosynthesis. Thus, photosynthesis along with respiration, helps to maintain the balance between O₂ and CO₂ in the environment.

4. Production of fuel: Due to natural disasters, like earthquake, plants get trapped under the soil and in due course of time get converted into coal and mineral oils. The energy obtained from these coal and mineral oils, is the solar energy which was entrapped by the plants in the past. This is how photosynthesis helps in the production of fuel.

5. Source of human welfare: We get different types of important materials from plants, like food, wood, paper, cloth, rubber, gum, paint etc. Apart from these, we get different alkaloids like morphine, quinine, reserpine etc. and various medicines from plants. Therefore, plants, more specifically photosynthesis, is very important for human welfare.

Question 6.
Write the role of chlorophyll in photosynthesis. How is photosynthesis related to the flow of energy in the environment?
Answer:
Role of chlorophyll in photosynthesis:
Chlorophyll gets excited by the absorption of photon particles of sunlight and dissociates the water absorbed by the root hairs into H⁺ and OH^– ions. Chlorophyll also converts the solar energy into the chemical energy which remains stored within ATP in the form of potential energy.

Relation of photosynthesis with energy flow in the environment The green plants trap solar energy and store it within ATP in form of chemical energy by photosynthesis. Later, this energy is converted to potential energy and remains stored within glucose, which is the end-product of photosynthesis.

On the other hand, a large part of potential energy, stored in glucose, is used up for performing various metabolic activities and is released as heat energy. The remaining potential energy enters the body of the primary consumers (herbivores), then secondary consumers carnivores. In this way, the energy reaches the ultimate consumers.

Decomposers, like various bacteria, fungi etc. act on the dead bodies of these consumers and the energy, thus, is recycled back into the environment through their decomposing activities. Thus, the solar energy returns to the environment after passing through producers and various consumers and decomposers. In this way, photosynthesis is related with energy flow in the environment.

Detailed explanations in West Bengal Board Class 9 Life Science Book Solutions Chapter 3.4 Circulation offer valuable context and analysis.

WBBSE Class 9 Science Chapter 3.4 Question Answer – Circulation

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

Question 1.
Which system of animal body can be treated as the system of transport?
Answer:
Circulatory system of animal body can be treated as the system of transport.

Question 2.
Which components of human circulatory system do act as vehicle?
Answer:
Blood and lymph of the human circulatory system act as vehicle of transport.

Question 3.
Which gases are transported through blood?
Answer:
Oxygen and carbon dioxide are transported through blood.

Question 4.
Which type of secretory products are transported through blood.
Answer:
Hormones are the main secretory products, transported through blood.

Question 5.
What does pulse rate indicate?
Answer:
Pulse rate indicates the rate at which the heart beats.

Question 6.
In which type of circulation different organs bathe in blood?
Answer:
In open circulatory system different organs bathe in blood.

Question 7.
From which body cavity blood enters into the heart of a cockroach?
Answer:
Blood enters into the heart of a cockroach from the pericardial sinus.

Question 8.
Why does blood of earthworm appear red?
Answer:
Blood plasma of earthworm contains haemoglobin, so it appears red.

Question 9.
Which is the largest sinus of insect body?
Answer:
Visceral sinus is the largest sinus of insect body.

Question 10.
How many ventricles does insect heart possess?
Answer:
Insect heart possesses thirteen ventricles.

Question 11.
Name an invertebrate animal, which possesses closed circulatory system.
Answer:
Earthworm possesses closed circulatory system.

Question 12.
Name an animal, in which blood does not take part in the transportation of the respiratory gases.
Answer:
In cockroach, blood has no role in the transportation of the respiratory gases.

Question 13.
Name a nutritionally important plasma protein.
Answer:
Albumin is a nutritionally important plasma protein.

Question 14.
Name an immunologically important plasma protein.
Answer:
Globulin is an immunologically important plasma protein.

Question 15.
Which disease is caused due to deficiency of red blood cells?
Answer:
Anaemia is caused due to the deficiency of red blood cells.

Question 16.
Which part of human circulatory system has the highest immunological importance?
Answer:
The lymph glands of human circulatory system have the highest immunological importance.

Question 17.
Which type / types of blood can be transfused to a person carrying ‘O’ blood group?
Answer:
A person with ‘O’ blood group can receive the ‘O’ group of blood only.

Question 18.
Which is the largest cell in the human blood?
Answer:
Monocyte is the largest cell in the human blood (Diameter. 12-18 μ m)

Question 19.
Which is the smallest cell in human blood?
Answer:
Platelet is the smallest cells in human blood. (Diameter, 2.5 μ m)

Question 20.
Which blood cells of human blood prevent blood coagulation inside blood vessels?
Answer:
Basophils prevent blood coagulation inside the blood vessels.

Question 21.
Which are the non-nucleated cells of the human blood?
Answer:
Platelets and matured red blood cells are the non-nucleated cells of the human blood.

Question 22.
Which blood cells of human blood take part in antibody formation?
Answer:
Lymphocytes take part in antibody formation.

Question 23.
Increase of which blood cell indicates blood cancer?
Answer:
Excessive and uncontrolled increase of WBC indicates blood cancer.

Question 24.
Who discovered the ABO blood grouping technique?
Answer:
Dr. Karl Landsteiner discovered the ABO blood grouping technique.

Question 25.
A baby is suffering from erythroblastosis foetalis. His father carries Rh⁺ blood. Which type of blood is expected in his mother?
Answer:
Mother of the baby is expected to carry Rh^– blood.

Question 26.
Which blood cell prevents allergy?
Answer:
Eosinophils prevent allergy.

Question 27.
Which blood cells are involved in transportation of respiratory gases?
Answer:
Erythrocytes (RBC) are involved in the transportation of the respiratory gases.

Question 28.
Which blood cell is the most abundant in human blood?
Answer:
RBC is the most abundant in human blood.

Question 29.
Which blood coagulating factor is possessed by platelets?
Answer:
Thromboplastin is the blood coagulating factor possessed by platelets.

Question 30.
Which element is essential for activating thromboplastin?
Answer:
Calcium ion is essential for activating thromboplastin.

Question 31.
Which two valves are commoniy called semilunar valves?
Answer:
Aortic valve and pulmonary arterial valves are commonly called semilunar valve.

Question 32.
How many heartbeats are generated by a healthy sinoatrial node?
Answer:
Sinoatrial node generates 70-80 heartbeats per minute.

Question 33.
Which junctional tissue supplements the function of a defective SA node?
Answer:
AV node or atrioventricular node supplements the function of a defective SA node.

Question 34.
Which part of special cardiac junctional tissue supply impulse to ventricular wall?
Answer:
Purkinje fibres supply impulse to the ventricular wall.

Question 35.
Which blood vessels carry oxygenated blood towards heart?
Answer:
Pulmonary veins carry oxygenated blood towards heart.

Question 36.
Which chamber of human heart receives deoxygenated blood?
Answer:
The right atrium receives deoxygenated blood.

Question 37.
How long does RBC survive?
Answer:
Normal life span of RBC is 120 days.

Question 38.
What is pericardium?
Answer:
Pericardium is the membranous outer covering of the heart.

Question 39.
What are systole and diastole?
Answer:
Contraction of the heart is called systole and relaxation of the heart is called diastole.

Question 40.
Which instrument is used to measure haemoglobin in blood?
Answer:
Haemoglobinometer is used to measure haemoglobin in blood.

Question 41.
What is haemoglobin made up of?
Answer:
Haemoglobin is made up of an iron part, called haem, and a protein part, called globin.

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

Question 1.
What is meant by circulation?
Answer:
Circulation is the physiological process by which nutrients, respiratory gases, hormones, minerals etc. are supplied to all the tissues of the body and the metabolic waste matters, produced inside the cells are transported to the respective excretory organs through fluid medium.

Question 2.
What is heart?
Answer:
Heart is a muscular, multi-chambered (2 in fishes, 3 in amphibians and reptiles, 4 in birds and mammals and 13 in insects) sac-like structure, which continuously pumps blood in a rhythmic manner into arteries and receives blood from the veins and in this process, helps the blood to flow through the network of vessels to every part of the human body.

Question 3.
What are arteries?
Answer:
Arteries are thick-walled blood vessels with roundish lumen, which carry oxygenated blood (exception-pulmonary arteries) from heart to the tissues with continuous rhythmic pulsation.

Question 4.
What are veins?
Answer:
Veins are the blood vessels with thinner wall and flattish lumen, which carry deoxygenated blood (exception-pulmonary vein) from the tissues to the heart and possess valves to maintain unidirectional blood flow.

Question 5.
What are capillaries?
Answer:
Capillaries are the finest of blood vessels with very thin wall, present in between arteries and veins. These fine vessels reach deep in the tissues to supply nutrients, oxygen etc. to the tissue fluid through diffusion and to collect the excretory materials and hormones from the tissues and the glands respectively.

Question 6.
What is meant by circulatory system?
Answer:
The system of organs, involved in supplying nutrients, respiratory gases, hormones to different tissues of the body and removing metabolic wastes from the body, is known as circulatory system.

Question 7.
What is meant by open circulation?
Answer:
The type of circulation, where body fluid does not remain confined within vessels, but pumped by the heart into open body cavity (haemocoel) to come in direct contact with the tissues, is called open circulation. This type of circulation is seen in molluscs, arthropods etc.

Question 8.
What is meant by closed circulation?
Answer:
The type of circulation, where blood flows through heart and network of blood vessels within the body and never opens in the body cavity, is called closed circulation. This type of circulation is noticed in all vertebrates and a few invertebrates like earthworm, leech etc.

Question 9.
What is blood?
Answer:
Blood is a red coloured, thick, faintly salty and alkaline, opaque, vascular connective tissue, composed of different types of cells suspended in a liquid matrix (plasma), which is pumped by the heart to flow through vessels for the transport of nutrients, respiratory gases, hormones, excretory substances and several other materials to all the parts of body.

Question 10.
What is haemolymph?
Answer:
Haemolymph is a colourless fluid, composed of a watery matrix and a few cells, flowing through the body cavity (haemocoel) of insects and other arthropods.

Question 11.
What is lymph?
Answer:
Lymph is a yellowish, transparent, modified tissue fluid, involved in absorption and transportation of nutrients, dissolved gases, immunologically important materials and different secretory and excretory substances into the tissues of higher animals.

Question 12.
Where do you find lymph in human body?
Answer:
Lymph is present in lymph vessels and lymph glands. Lymph glands are localised in certain regions of the body viz. around neck, breasts, armpits, groin etc. of a human body.

Question 13.
What is CSF? Where is it found?
Answer:
CSF: CSF or cerebrospinal fluid is a typical fluid, present in the central nervous system (CNS) of vertebrates.
0ccurrence of CSF: CSF is present in the ventricles of brain and in the central canal of the spinal cord. This fluid is also present in the subarachnoid space (between the second and third covering layers of brain or meninges).

Question 14.
What is synovial fluid? What does it do?
Answer:
Synovial fluid: Synovial fluid is a slightly viscous, colourless body fluid typically present in the membrane-bound synovial cavities in between movable bone joints.
Function: Synovial fluid protects bone ends against frictional damage and supplies nutrients.

Question 15.
What is tissue fiuid? What is its function in animal body?
Answer:
Tissue fluid: Tissue fluid is the extracellular fluid present in the tissues of multicellular animals.
Function: Tissue fluid helps in the transportation of nutrients, respiratory gases, hormones and metabolic waste materials.

Question 16.
What is meant by cytosol?
Answer:
Cytosol is a bulk of intracellular fluid present in the cytoplasm. Different types of intracellular fluids are present in different cell organelles like mitochondria, Golgi body, plastid, endoplasmic reticulum, lysosome, vacuoles etc. performing their respective functions.

Question 17.
How is water utilised in human body?
Answer:
Water is utilised in the human body in different ways as follows-

• It acts as the main component of the protoplasm
• Helps in hydrolysis of food matters in digestion
• Acts as the medium of diffusion and osmosis for nutrients, respiratory gases, metabolic wastes and hormones.

Question 18.
Mention the characteristic features of matured human RBC.
Answer:
Matured human RBC is a round shaped anucleated biconcave, membrane-bound cell. It contains haemoglobin within cytoplasm but devoid of mitochondria and nucleus. The cell is 7.2 μ m in diameter and 2.6 μ m in thickness. Number of RBC is 5 million / ml in male & 4.5 million / ml in female. Its average life span is 120 days.

Question 19.
Mention the functions of RBC.
Answer:
Functions of RBC are as follows-

1. RBCs transport respiratory gases.
2. They maintain acid-base balance in the plasma.
3. They maintain ionic equilibrium.
4. They help in the formation of colour of faeces.

Question 20.
From where do RBCs originate in human body?
Answer:
RBCs originate from-

• Vasculosa region of early embryo.
• Spleen and liver of matured foetus, about one month before birth
• Red bone marrow after birth.

Question 21.
Mention the structural features and function of neutrophils.
Answer:
Structural features: Neutrophils are amoeboid WBC with a diameter of 10-12 μ m. Its cytoplasm is granular and the nucleus has 2-7 lobes.
Function: Neutrophils kill germs by the process of phagocytosis.

Question 22.
Mention the structural features and function of eosinophil.
Answer:
Structural features: Eosinophils are amoeboid WBC with a diameter of 10-12 μ m. Its cytoplasm is granular and the nucleus has 2-3 lobes.
Function: Eosinophils play important role in preventing allergy.

Question 23.
Mention the structural features and function of basophil.
Answer:
Structural features: Basophil is a granulocytic WBC with a diameter of 8-10 μ m. The nucleus of basophil is bean-shaped.
Function: Basophils secrete an anti-coagulant to prevent coagulation of blood within blood vessels.

Question 24.
Mention the structural features and function of monocytes.
Answer:
Structural features: Monocytes are agranulocytic WBC with a diameter of 7.5-12 μ m. It contains a round or kidney-shaped nucleus and homogenous cytoplasm.
Function: Monocytes kill germs by the process of phagocytosis.

Question 25.
Mention the structural features and function of lymphocytes.
Answer:
Structural features: Lymphocytes are agranulocytic WBC with a diameter of 14-18 μ m. It contains a horse-shoe shaped nucleus and homogenous cytoplasm.
Function: Lymphocytes prepare antibody to maintain immunity.

Question 26
Mention the structural features and function of platelets or thrombocytes.
Answer:
Structural features: Platelets or thrombocytes have oval or water droplet-like cell without nucleus. This blood cell is only 2.5 μ m in diameter, treated as the smallest cell in human body.
Functions: When platelets are broken, thromboplastin is released from them to initiate the reactions of blood coagulation.

Question 27.
What is meant by ABO blood group?
Answer:
In 1901, Karl Landsteiner classified human blood into four groups, on the basis of distribution of agglutinogens (antigens) on RBC & agglutinins (antibodies) in plasma. There are two types of agglutinogens (A and B) & two types of agglutinins (α and β) found in blood. Based on this distribution human blood is classified into A, B, AB and O groups. This system of classification of blood is called ABO blood group.

Question 28.
Mention the distribution of agglutinins and agglutinogens in different blood groups in a tabular form.
Answer:
The following table shows the distribution of agglutinins and agglutinogens in different blood groups.

Blood group	Agglutinogens in RBC	Agglutinins in plasma
Group A	A	β
Group B	B	α
Group AB	A and B	Agglutinin absent
Group O	Agglutinogen absent	α and β

Question 29.
What is meant by universal donor of blood?
Answer:
Due to absence of agglutinogen in RBC, a person having blood group ‘ O ‘ can donate blood to any group. In this case, chance of haemagglutination does not arise. Therefore, an individual having blood group ‘O’ is called universal donor.

Question 30.
What is meant by universal recipient of blood?
Answer:
Due to absence of any agglutinin in plasma, people having blood group ‘AB’ can receive blood from any group. In this case, chance of haemagglutination does not arise. Therefore, an individual having blood group ‘AB’ is called universal recipient.

Question 31.
What is Rh factor?
Answer:
Rh factor is an antigenic protein present in the RBC of most of the world’s population, which has close similarity with a factor present in RBC of Indian monkey Rhesus macaques. The people having this factor are treated as Rh⁺whereas those do not having it are regarded as Rh^–

Question 32.
Mention the importance of Rh factor in blood transfusion.
Answer:
If a person without Rh factor (Rh^–) is transfused with blood from a person carrying Rh factor (Rh⁺), after 12 days, an antibody, called anti-Rh factor, develops in the recipient’s blood. In case the same person gets a second transfusion with Rh⁺blood, a reaction will take place between Rh factor (antigen) and anti-Rh factors (antibody) in his blood. This will lead to a fatal consequence due to agglutination and haemolysis of RBC.

Question 33.
What is erythroblastosis foetalis?
Answer:
If an Rh^–mother carries a Rh⁺foetus, the Rh antigen enters into mother’s blood from the foetus. In this situation, anti-Rh factor (antibody) develops in mother’s blood, which comes back to Rh⁺foetus and destroys the foetal RBC. As a result, the baby is born with serious anaemia. This is called erythroblastosis foetalis.

Question 34.
What is meant by blood transfusion? Mention its importance.
Answer:
Blood transfusion: Blood transfusion is a technique of intravenous infusion of blood to a person who is deficient of blood or blood components.
importance: Blood is something, which cannot be prepared by any means. Therefore, a patient, suffering from severe anaemia or excessive blood loss has to be transfused with blood to replenish the need.

Question 35.
What is meant by blood clotting? Mention its importance.
Answer:
Blood clotting: Blood clotting is a physiochemical process by which blood turns into a semisolid jelly-like mass or clot.
importance: Blood clots at the opening of a wound within a few minutes, hereby, stops bleeding and prevents excessive blood loss.

Question 36.
Mention different layers of the the walls of human heart.
Answer:
The wall of heart has three layers. These are-

• Epicardium (outermost layer)
• Myocardium (middle layer)
• Endocardium (innermost layer)

Question 37.
What is mitral valve? What does mitral valve do?
Answer:
Mitral valve: Mitral valve or bicuspid valve is the double cusped valve present at the left atrioventricular opening of the human heart.
Function: Mitral valve allows blood to flow from left atrium to left ventricle but prevents its backflow.

Question 38.
What is tricuspid valve? What does it do?
Answer:
Tricuspid valve: Tricuspid valve is the triplecusped valve present at the right atrioventricular opening of the human heart.
Function: Tricuspid valve allows blood to flow from right atrium to right ventricle but prevents the backflow.

Question 39.
What do semilunar valves do?
Answer:
In heart, the atrial semilunar valve allows the flow of oxygenated blood from the left ventricle through the aorta and prevents the backflow of blood. The pulmonary semilunar valve allows deoxygenated blood from the right ventricle to flow through the pulmonary artery and prevents the backflow.

Question 40.
What are papillary muscles?
Answer:
The inner surface of the ventricular wall of heart gives off many inwardly directed columnar muscular projections. These projections are called papillary muscles.

Question 41.
What are chordae tendineae?
Answer:
From the tip of the papillary muscles, inside ventricle, some strong cord-like tendons arise, these are called chordae tendineae.

Question 42.
Mention the role of chordae tendineae?
Answer:
The chordae tendineae attach to the ventricular face of the cusps of right and left atrioventricular valves. When the ventricles contract, these strong cords prevent the valves against opening towards the atria.

Question 43.
Distinguish between open and closed circulation.
Answer:

Features	Open circulation	Closed circulation
1. Body cavity	Blood opens in the body cavity	Blood remains confined in the blood vessels
2. Capillaries	Capillaries absent	Capiliaries present
3. Blood cells	Very few cells are present in the matrix	Different cells are present in liquid matrix Exception – Invertebrates
4. Occurrence	Arthropods and molluscs	Annelids and vertebrates

Question 44.
Distinguish between human blood and lymph.
Answer:

Features	RBC, all types of WBCs and platelets	Lymph
1. Cellular components	Red	Lymphocytes only
2. Colour	Does not come in direct contact with the tissue fluid	Faintly yellow
3. Relation with tissue fluid	Coagulates faster	Comes in direct contact with the tissue fluid
4. Coagulation	RBC, all types of WBCs and platelets	Coagulates slowly

Question 45.
Distinguish between plasma and serum.
Answer:

Features	Plasma	Serum
1. Nature	Matrix of blood	Watery portion of clotted blood
2. Fibrinogen	Present	Absent
3. Coagulating factors	Present	Absent
4. Coagulation	Occurs slowly	Does not coagulate

Question 46.
Distinguish between haemoglobin and haemocyanin.
Answer:

Features	Haemoglobin	Haemocyanin
1. Metallic component	Iron	Copper
2. Colour	Red	Faintly bluish
3. Occurrence	Plasma of some invertebrates and in RBC of vertebrates	Body fluid of crustacean, arthropods and molluscs
4. Transportation of respiratory gases	Carries O2 and CO2	Carries O2 only

Question 47.
Distinguish between universal donor and universal recipient.
Answer:

Features	Universal donor	Universal recipient
1. Blood group	group	AB group
2. Agglutinin	α and β	Absent
3. Agglutinogen	Absent	A and B
4. Compatibility	Can donate blood to any group but can receive the same blood group only	Can receive blood from any group but can donate to the same group only

Question 48.
Distinguish between artery and vein.
Answer:

Features	Artery	Vein
1. Origin and termination	Originates from the heart and terminates into the capillaries	Originates from the capillaries and terminates in the heart
2. Walls and lumen	Walls thick, lumen roundish	Walls thinner, lumen flattish
3. Valves	Absent	Present
4. Pulsating movement	Occurs	Does not occur
5. Function	Carries oxygenated blood (except pulmonary artery)	Carries deoxygenated blood (except pulmonary vein)

Question 49.
Distinguish between auricle and ventricle.
Answer:

Features	Auricle	Ventricle
1. Position	Upper portion of the heart	Lower portion of the heart
2. Wall	Thinner and less muscular	Thicker and highly muscular
3. Inner surface	Smooth	Projects papillary muscles
4. Function	Receives blood from the veins (superior and inferior vena cava, and pulmonary vein)	Circulates blood through the arteries (pulmonary artery, aorta)

Question 50.
Distinguish between systemic circulation and pulmonary circulation.
Answer:

Features	Systemic circulation	Pulmonary circulation
1. Course of circulation	From the heart to different organs (except lungs) and back	From the lungs to heart and back
2. Nature of blood	Oxygenated blood	Deoxygenated blood
3. Size of vessels	Long and elaborate	Short and compact
4. Connection to lymphatic ducts	Lymphatic ducts join to it	Lymphatic ducts do not join to it

Question 51.
Distinguish between CSF and synovial fluid.
Answer:

Features	CSF	Synovial fluid
1. Occurrence	In ventricles and lumens of the central nervous system	In spaces of movable bone joints
2. Function	Transportation of nutrients, respiratory gases and excretory matters, and acts as a shock absorber	Protection against frictional damage

Question 52.
Distinguish between tissue fluid and intercellular fluid.
Answer:

Features	Tissue fluid	Intercellular fluid
1. Occurrence	Inside the spaces within the tissues	In the spaces between the cells
2. Function	Keeps tissue-cells alive by supplying nutrients	Helps in the diffusion and osmosis of important materials

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

Question 1.
What is circulation? Mention the importance of circulation in living organisms. 1 + 4
Answer:
Circulation
Circulation is the physiological process by which nutrients, respiratory gases, hormones and metabolic waste matters are transported within a body through a fluid medium.

Importances of circulation
Circulation is important for the living organisms for the following purposes.

1. Movement of nutrients and minerals: Water, essential minerals, food materials are transported to all tissues of a living body by means of circulation.
2. Transport of respiratory gases: Respiratory gases, such as O₂ and CO₂, are transported within the body through the process of circulation.
3. Removal of metabolic wastes: The unwanted matters, produced in the cells from metabolic activities are transported from the tissues to excretory organs for elimination.
4. Movement of synthesized materials: Hormones, synthesized in cells, are transported to their target organs by means of circulation.
5. Maintenance of heat: Circulatory fluid maintains the body heat in warm-blooded animals.
6. Storage: Amino acids are stored in the circulatory fluid (blood) to form an amino acid pool. Some lipids (cholesterol) are also stored in the blood.

Question 2.
Give a brief account of the different components of human circulatory system.
Answer:
Components of human circulatory system
Human circulatory system is composed of three major components-

• circulating fluids.
• vessels.
• a pumping organ (heart).

1. Circulating fluids: Blood and lymph are the circulating fluids of human circulatory system.

Blood: Blood is the red coloured fluid connective tissue, which carries different important materials through the blood vessels.
Lymph: Lymph is a special tissue fluid that flows through the lymphatic ducts and lymph glands and acts as another transporting medium.

2. Vessels: Blood flows through three types of vessels, which form an intricate network in the human body. These are-arteries, veins and capillaries.
Arteries: Arteries are thick-walled vessels with roundish lumen. They carry oxygenated blood (exceptionpulmonary arteries) from the heart to the tissues. Arteries show rhythmic pulsation.
Veins: Veins have thinner wall and flattish lumen. Veins carry deoxygenated blood (exception-pulmonary vein) from the tissues to the heart. They have valves to maintain the unidirectional blood flow.
Capillaries: These are very thin-walled blood vessels present in between the arteries and the veins. These fine vessels reach deep in the tissues.

3. Heart: It is a muscular, four-chambered sack-like structure, which pumps blood continuously into arteries and helps blood to flow through the network of vessels in the human body.

Question 3.
Schematically mention different types of blood corpuscles of human body.
Answer:
Different types of blood corpuscles or cells of human body

Question 4.
Mention the functions of lymph, cerebrospinal fluid and sweat. 2 + 2 + 1
Answer:
Functions of lymph
The functions of lymph are as follows-

1. It supplies nutrients and oxygen deep into the tissues,
2. Lymphocyte cells and antibodies present in the lymph, kill germs
3. Absorbs fat from the intestine
4. It collects the metabolic wastes from the tissue fluid
5. Lymph maintains pressure, volume and composition of the tissue fluids.

Functions of cerebrospinal fluid
The functions of cerebrospinal fluid are mentioned below.

• Acts as a shock absorber for the brain & spinal cord
• Supplies nutrition and oxygen to the brain tissue
• Helps in the removal of metabolic wastes from the CNS.

Functions of sweat
The functions of sweat are as mentioned below.
1. It maintains the acid-base balance, water balance and the body temperature.
2. Some salts, urea and many other materials are excreted through sweat.

Question 5.
What is plasma? Briefly represent the composition of plasma. 1 + 4
Answer:
Plasma :
Plasma is the yellowish, slightly alkaline, transparent watery matrix of blood.

Composition of plasma :
Plasma contains water (91-92%) and solid matters (8-9%). These solid matters include different inorganic and organic materials.
1.  Inorganic matters of plasma (0.9 %) : Compounds of sodium, potassium, calcium, magnesium, phosphorus, iron, copper, chlorine, iodine etc.
2 Organic matters of plasma (7-8 %) : Organic matters of plasma are mentioned below.

• Sugar-glucose
• Protein-serum albumin, serum globulin, prothrombin, fibrinogen etc.
• Fat-cholesterol, lecithin, phospholipids, neutral fat molecules.
• Non-protein nitrogenous compounds-urea, uric acids, ammonia, creatinine, creatine etc.
• Pigments-bilirubin, biliverdin, β-carotene etc.
• Secreted materials-hormones, enzymes etc.
• Gases-oxygen, carbon dioxide etc.

Question 6.
Mention the functions of blood plasma? How is water utilised in human body? 3 + 2
Answer:
Functions of blood plasma –
The functions of blood plasma are mentioned below.

1. Plasma helps in transportation of nutrients, metabolic waste matters, hormones etc.
2. It maintains acid-base balance of the body.
3. Plasma proteins develop immunity and provide protection against many diseases.
4. Plasma proteins, like prothrombin and fibrinogen, help in blood clotting.

Utility of water in human body
Water is utilised in the human body in different ways which are mentioned below.

1. Water acts as the main component of the protoplasm.
2. It helps in the hydrolysis of food matters in digestion.
3. Water acts as the medium of diffusion and osmosis for nutrients, respiratory gases, metabolic wastes and hormones.

Question 7.
Briefly describe the role of blood in human body.
Answer:
Functions of blood in human body
For human life, blood is an ultimate essentiality. We need blood for-
1. Iransportation of O₂, CO₂ and nutrients: Blood carries O₂ and nutrients to different tissues and carries CO₂ to lungs.
2. Removal of the metabolic wastes: Blood collect excretory matters from the tissues and carries those materials to respective excretory organs.
3. Movement of hormones from glands to target organs: Hormones, secreted from the hormone glands are transported to the tissues or other glands by blood.
4. Maintenance of body temperature: Blood carries glucose to all the tissues, which generate heat by oxidation to maintain the body temperature.
5. Resistance against infections: Neutrophils and monocytes kill germs by phagocytosis. Lymphocytes produce antibody. Thus, blood resists infection.
6. Preventing blood loss: Excessive loss of blood from wounds is restricted by its coagulating ability.

Question 8.
Explain the significance of blood grouping. How do you inspire somebody for blood donation? 2 + 3
Answer:
Significance of blood grouping
Due to the presence of various agglutinogens and agglutinins, transfusion is not possible among all groups. If donor’s and recipient’s blood react to cause agglutination (antigen-antibody reaction i.e. coagulation of RBC), their blood groups will be treated as mismatch or incompatible. There will be no agglutination if the blood groups are compatible. In case of incompatible transfusion, agglutinogen of donor’s RBC reacts with agglutinin of recipient’s plasma to cause agglutination.

Ways to inspire somebody for blood donation
To inspire somebody for blood donation, I shall try to eliminate his on her misconceptions regarding blood donation by saying that-

1. Blood donation causes no harm to the donor.
2. The donated blood is replenished within a week.
3. Blood donation reduces the chance of heart attack and hypertension.
4. Blood can not be created artificially. So donated blood can save any needy patients life.
5. It is a noble gesture of a person towards the society.

Question 9.
Mention the mechanism of blood coagulation in brief.
Answer:
Mechanism of blood coagulation
The components involved in the main steps of blood clotting are enzyme thrombokinase or thromboplastin, calcium ion, plasma proteins like prothrombin and fibrinogen. The main steps of blood clotting are mentioned below.
1. Some blood platelets break near the wounds. From broken platelets enzyme Platelet-thromboplastin and from damaged tissue, tissuethromboplastin are secreted.

2. These two enzymes, with other proteins and Ca²⁺ prepare another enzyme named prothrombinase. This enzyme inactivates heparin and activates prothrombin into thrombin. This reaction is helped by calcium ions (Ca²⁺).

3. This thrombin then reacts with another plasma protein, fibrinogen, to produce fine thread-like fibrin molecules. In this reaction also calcium ions play a supporting role. The fibrin molecules form a dense network at the opening of the wound. The blood cells get trapped in that net. Within a few minutes blood at that point is transformed into a thick, viscous, jelly-like mass, called thrombus. This thrombus plugs the wound and stops bleeding.

Question 10.
Briefly describe the structure of human heart.
Answer:
Structure of heart
Human heart is a hollow, muscular, blunt-ended conical sac-like structure. It is externally covered with a bilayered coating called pericardium.
If a human heart is cut longitudinally, we can see the following anatomical features in it.

1. Chambers of the heart: Human heart has four chambers. The upper two are called auricles or atria and the two, at the lower side are the ventricles.
Auricles or atria: Auricles have comparatively thinner wall. According to the relative position, these are denoted as left and right atria. The two atria are separated by inter-atrial septum.

Ventricles: These two chambers are located lower to the auricles. Ventricular walls are more thick and muscular. A thick inter-ventricular septum separates the two ventricles.

2. Valves of heart: The left and the right atria are connected to respective ventricles with two openings, called left and right atrioventricular apertures. These two apertures are fitted with two valves. The right atrioventricular valve has three cusps (flaps), so it is called tricuspid valve. The left one has two cusps, so it is called bicuspid valve or mitral valve.

The exits of aorta and pulmonary trunk are fitted with two outwardly directed valves. These are known as aortic valve and pulmonary valve respectively. These are commonly called semilunar valves because of their half moon-shaped cusps.

Question 11.
Describe the structure of pacemaker system of human heart.
Answer:
Structure of pacemaker system of human heart
The pacemaker of human heart is made up of a few cardiac muscle cells, specialized to generate spontaneous impulse within the heart. This impulse is spread all over the heart and makes it beat continuously in a rhythm. These tissues are called the junctional tissues or pacemaker of the heart.

The main impulse generating centre of the heart is called sinoatrial node (SA node), located near the junction of superior vena cava and right auricle. It can generate 70-80 beats / min. The next centre is atrioventricular node (AV node), positioned at right atrioventricular wall. It can take over the charge from an inactive SA node and can generate 60-70 beats/ min. SA node and AV nodes are interconnected by three pairs of internodal connectors. From AV node a bundle of junctional tissues comes down through the interventricular septum. This is called bundle of His. This bundle is also capable of generating about 50 beats / min. This bundle then ramifies into several branches and spread in the ventricular wall as Purkinje fibres.

Question 12.
Briefly describe the course of circulation through human heart.
Answer:
Course of circulation through human heart
Human heart beats spontaneously in a rhythmic fashion. Due to this contraction and expansion movement, blood is pumped through the blood vessels and circulates in the body. The contraction and expansion of the heart is called systole and diastole respectively. During systole and diastole following events occur in different chambers of the heart.
1. Diastole of auricles: In this phase the auricles expand and auriculoventricular valves close. Pressure decreases in the auricles. Soon deoxygenated blood from superior and inferior vena cava and coronary sinus enters into right auricle. At the same time oxygenated blood from pulmonary veins enters into left auricle.

2. Systole of auricles: As the auricles get completely filled, they contract. Pressure increases in the auricle. With this pressure, both tricuspid and bicuspid valves open towards right and left ventricles respectively.

3. Diastole of ventricles: Diastole of ventricles starts with the systole of auricles. With the opening of tricuspid and bicuspid valves deoxygenated blood enters into right ventricle and oxygenated blood rushes into left ventricle respectively.

4. Systole of ventricles: When the two ventricles get filled with blood, ventricular systole starts. So pressure increases inside these chambers. With this pressure tricuspid and bicuspid valves close with a jerk. With maximum ventricular pressure the pulmonary and aortic valves open at a time. Then deoxygenated blood from right ventricle and oxygenated blood from left ventricle are pumped out through pulmonary trunk and aorta respectively.

In human heart, blood flows through two separate circuits. The right portion of it carries deoxygenated blood and oxygenated blood flows through the left portion. In a normal human heart, mixing of two different types of blood never happens. Therefore, human heart acts as a perfectly double circuit heart.

Question 13.
Draw a line diagram of L.S. of human heart to show the course of circulation through it, with labelling.
Answer:
Diagram of human heart
Following is a labelled diagram of L.S. of human heart showing course of circulation through it.

Question 14.
What is meant by double circulation? Show the path of double circulation with a schematic diagram. 2 + 3
Answer:
Double circulation
In higher vertebrates like birds and mammals, heart is four chambered. Here blood flows in two separate circuits, one through systemic path and the other through pulmonary path. This type of circulation is known as double circulation. It is called a double circulatory system, since it has two loops. The one is from the heart to the lungs and the other is from the heart to the rest of the body.

Diagram of double circulation path –
The following labelled diagram shows the path of double circulation.

Question 15.
Comparison among human RBC, WBC and platelets.
Answer:

Detailed explanations in West Bengal Board Class 9 Life Science Book Solutions Chapter 2.4 Major Organs of Human Body and Their Function offer valuable context and analysis.

WBBSE Class 9 Science Chapter 2.4 Question Answer – Major Organs of Human Body and Their Function

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

Question 1.
Which two layers constitute our skin?
Answer:
Epidermis and hypodermis constitute our skin.

Question 2.
Which is the largest sense organ of our body?
Answer:
Skin is the largest sense organ of our body.

Question 3.
Which organ of our body carries the sensory cells for perception of heat and pressure?
Answer:
Skin of our body carries the sensory cells for perception of heat and pressure.

Question 4.
Which organ of our body can store the food for some time during digestion?
Answer:
Stomach of our body can store the food for some time during digestion.

Question 5.
Which gland of human body is called a mixed gland?
Answer:
Pancreas is called the mixed gland.

Question 6.
Which organ of the human digestive system acts as the killing field for most of the microbes, taken with food?
Answer:
Stomach of human digestive system acts as the killing field for most of the microbes, which are taken with food.

Question 7.
Besides killing germs within the consumed food, what other function does HCl do inside stomach?
Answer:
Besides killing germs within the consumed food, HCl activates pepsinogen into pepsin inside the stomach.

Question 8.
Name the paired organs which are protected by ribbones from all sides.
Answer:
The lungs are the paired organs which are protected by ribbones from all sides.

Question 9.
Name the organ of human body which helps in neutralising the acidic food mass, coming into duodenum from the stomach.
Answer:
Liver, of our body secretes bile, which neutralises the acidic food mass, coming into duodenum from the stomach.

Question 10.
Which organ is located just below the stomach at the left side of the abdomen?
Answer:
The organ located just below the stomach at the left side of the abdomen is the spleen.

Question 11.
Name the largest gland of human body which is composed of densely packed tissues.
Answer:
Liver is the largest gland of human body composed of densely packed tissues.

Question 12.
Name a highly extensible sac-like structure located at the left side of the upper abdomen.
Answer:
Stomach is a highly extensible sac-like structure located at the left side of the upper abdomen.

Question 13.
Which organ removes dead RBCs from blood?
Answer:
Spleen removes dead RBCs from the blood.

Question 14.
This elongated cord-like structure acts as the centre for reflex action of our body. What is it?
Answer:
Spinal cord is the elongated cord-like structure, which acts as the centre for reflex action of our body.

Question 15.
The lumen of which organ always remains in acidic state?
Answer:
The lumen of stomach always remains in acidic state.

Question 16.
Which two organs of our body contract and expand continuously throughout our lives?
Answer:
Heart and lungs contract and expand continuously throughout our lives.

Question 17.
Which organ of our body remains protected in a roundish bony case known as cranium?
Answer:
Brain remains protected in a roundish bony case known as the cranium.

Question 18.
Which paired structures keep our blood clean from metabolic wastes?
Answer:
The kidneys keep our blood clean from metabolic wastes.

Question 19.
Name the organ of our body, through which blood passes along two different paths.
Answer:
Heart is the organ of our body, through which blood passes along two different paths.

Question 20.
What is the position of heart in human body?
Answer:
Hear is located in the chest cavity, in between the two lungs, slightly inclined towards the left.

Question 21.
Name the cells from which testosterone is secreted inside the testes of male.
Answer:
Testosterone is secreted from the leydig cells of the testes in male.

Question 22.
Name two hormones secreted by the corpus luteum in female.
Answer:
Two hormones secreted by the corpus luteum in female, are oestrogen and progesterone.

Question 23.
What is the process of production of ovum called?
Answer:
The process of production of ovum is called oogenesis.

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

Question 1.
What is meant by organ?
Answer:
An organised group of various specialised tissues which carry out a specific function of the body, is called an organ. Example-Heart, brain etc.

Question 2.
Mention the functions of skin of our body.
Answer:
The functions of skin are as follows-

• Skin protects our body from mechanical injuries.
• Enzymes and salts, secreted through sweat, kill bacteria and other germs.
• Sensory cells in skin help us to feel heat, touch, pressure etc.
• Skin absorbs sun rays to synthesise vitamin D for the body.

Question 3.
What is a sebaceous gland?
Answer:
The gland present in the dermis layer of the skin, that secretes an oily substance called sebum, which keeps the skin smooth, is called the sebaceous gland.

Question 4.
Mention the function of human heart.
Answer:
The functions of human heart are as follows —

• Pumping of heart helps the blood to flow through blood vessels of the body.
• It drives oxygenated blood from left ventricle through systematic circulation to different organs and tissues of the body.
• Deoxygenated blood from right ventricle goes out to lungs through pulmonary circulation.
• Heart receives deoxygenated and oxygenated blood into its right auricle and left auricle respectively.

Question 5.
Name a hormone and the major enzyme secreted by the stomach.
Answer:
Gastrin is a hormone secreted by the stomach and pepsin is the major enzyme secreted by the stomach.

Question 6.
Mention the location and function of human lungs.
Answer:
Location: The two lungs are situated at the two sides of chest cavity within the rib cage.
Function:

• Lungs help in the intake of O₂ rich air by inspiration and expulsion of CO₂ rich air by expiration.
• Lungs also help in the excretion of few other toxic materials by expiration.

Question 7
Name the two major blood vessels of the kidney and name the protective layer of kidney.
Answer:
The two major blood vessels of the kidney are the renal vein and renal artery and the protective layer of kidney is called capsule.

Question 8.
Mention the functions of the human brain.
Answer:
The functions of human brain are as follows —

• Brain processes all sensory informations like vision, smell, hearing, taste, touch etc. and generate responses accordingly.
• It acts as the centre for memory, intelligence, thinking and all other mental activities.
• Coordination among all organs of our body and their activities are maintained by the brain.

Question 9.
What is spinal cord? Mention the functions of spinal cord.
Answer:
Spinal cord: The long, hollow, cylindrical structure extending from the posterior parts of medulla oblongata upto first lumber vertebra in the neural canal of vertebral column, is known as spinal cord.

Function:

• Spinal cord receives the nerve impulses from brain and conducts it to the muscles and visceral organs.
• Spinal cord controls different types of unconditioned reflexes.

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

Question 1.
Describe the location of human stomach. Mention its functions.
Answer:
Location of human stomach
Stomach is situated on the left side of the upper abdomen, just below the muscular diaphragm.

Functions of human stomach
The functions of human stomach are as follows-

• Stomach is a large ‘J’ shaped sac-like structure that receives food from the oesophagus, stores it for some time and acts as a site of digestion of protein and fat.
• HCl, secreted from the oxyntic cells of stomach, helps in activating the gastric enzymes.
• Activated pepsin, present in gastric juice, acts upon proteins to break it into smaller derivatives, called peptones.
• Lipase, present in gastric juice, helps in the hydrolysis of fat.
• As the pH inside the stomach is acidic, microbes find it difficult to survive within it. Therefore, most microbes of the digestive flora remain within the gut and not in the stomach.

Question 2.
Mention the location of human liver. Mention its functions.
Answer:
Location of human liver
Liver is present on the right ventral side of upper abdomen, just below the diaphragm.

Functions of human liver:
The functions of human liver are as follows-

• Liver secretes bile, which neutralises the acidic contents of the stomach.
• Bile salts emulsify fat and help in its digestion.
• Liver primarily absorbs nutrients from blood before supplying it to different parts of the body.
• It acts as the site of several metabolic activities.
• Urea is synthesised within the liver.
• Liver detoxifies various harmful components of the blood, like urea.
• It helps in the synthesis of blood-coagulating components like prothrombin, fibrinogen, etc.

Question 3.
Mention the location and functions of human kidney. Mention the location and functions of the pancreas in the human body.
Answer:
Location of kidney
Kidneys are held at the back wall of abdominal cavity on either sides of the vertebral column. Right kidney is positioned slightly lower than the left one.

Functions of kidneys
The functions of kidneys are as follows-

• Formation of urine by filtration of blood.
• Maintains the water and electrolyte balance of our body.
• Regulates blood pressure by secretion of renin.
• Controls formation of RBC by secretion of erythropoietin.

Location of pancreas : Pancreas is located transversely on the posterior side of the abdomen, extending from the duodenum to the spleen.

Functions of pancreas
The functions of pancreas are as follows-

• It secretes different digestive enzymes for the digestion of proteins, carbohydrates and fats. The enzymes are trypsin, amylase and lipase.
• The pancreas produces essential hormones like insulin, glucagon and somatostatin in the body.

Question 4.
Mention the location of spleen in human body. Mention the functions of spleen.
Answer:
Location of spleen : Spleen of human body is located on the upper far left side of the abdomen, below the left side of the stomach.

Functions of spleen
The functions of spleen are mentioned below.

• In embryonic state, spleen acts as the site of RBC formation.
• In adults, it produces lymphocytes (B-cells and T-cells) to help the proper functioning of immune system.
• Spleen separates out and removes damaged, inactive and aged RBC from the blood stream.
• It stores large quantity of RBC and leucocytes and releases it into the blood stream according to the need of the body.

Question 5.
What is ovary? Mention the position of human ovary and its functions.
Answer:
Ovary: The primary sex organ or gonad of female body is called ovary.

Location of human ovary:
Human ovaries are located at the two sides of lower abdominal cavity in females. Each ovary is an almond shaped structure, which is held in the abdominal wall with a thin membranous structure, a fibrous cord, known as the ovarian ligament.

Functions of human ovary:
The functions of human ovary are mention below.

• Several primordial germ cells are present in the ovary, which ultimately mature as ovum or female reproductive cells.
• Ovary secretes hormones like oestrogen and progesterone. These two female hormones help to maintain the feminine features and reproductive cycle in female.
• Hormone relaxin, secreted from the ovary, facilitates labour during childbirth.

Question 6.
What is testis? Mention the location and functions of testis.
Answer:
Testis : The primary sex organ or gonad of male body is called testis.

Location of testis
Human testis are paired structures, which are held in a sac-like structure, called scrotum, outside the lower abdomen in males. These are placed in between the penis and anus.

Functions of testis
The functions of testis are mentioned below.

• Male gametes (spermatozoa) are formed within the seminiferous tubules of testis.
• Spermatozoa are nourished and stored inside the testis.
• Testis secretes a hormone, named testosterone, which controls the development of masculine features like formation of beard, muscular body etc. in adult male. It also controls the maturity of spermatozoa.

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.