Detailed explanations in West Bengal Board Class 9 Life Science Book Solutions Chapter 1.3D Classification of Kingdom Animalia offer valuable context and analysis.

WBBSE Class 9 Science Chapter 1.3D Question Answer – Classification of Kingdom Animalia

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

Question 1.
In tripioblastic animals, which germinal layer is present in between ectoderm and endoderm?
Answer:
In triploblastic animals, mesoderm layer is present in between ectoderm and endoderm.

Question 2.
Name a phylum in which mesenchyme is present in between ectoderm and endoderm?
Answer:
In phylum Porifera, mesenchyme is present between ectoderm and endoderm.

Question 3.
Animals of which phylum possess pseudocoelom?
Answer:
Animals of phylum Nematoda possess pseudocoelom.

Question 4.
Members of which phylum use setae or parapodia for locomotion?
Answer:
Animals of phylum Annelida use setae or parapodia for locomotion.

Question 5.
In which group of animals do you find both external and internal segmentation?
Answer:
Animals under phylum Annelida have both external and internal segmentation.

Question 6.
What is paragastric cavity?
Answer:
The cavity, present inside the body of poriferans, is called paragastric cavity.

Question 7.
What is coelenteron?
Answer:
The central tubular gastrovascular body cavity present in Cnidarians is called coelenteron.

Question 8.
What is coelom?
Answer:
Coelom is the fluid-filled cavity inside animal body surrounded by mesodermal lining.

Question 9.
What is haemocoel?
Answer:
Haemocoel is the blood-filled coelomic body cavity, found in arthropods and molluscs.

Question 10.
What is pseudocoeiom?
Answer:
Pseudocoelom is a body cavity, typically seen in nematodes, which is not surrounded by mesodermal lining.

Question 11.
What are setae?
Answer:
Setae are minute bristle-like structures, which earthworms and some other annelids use for locomotion.

Question 12.
What are parapodia?
Answer:
Parapodia are unjointed, lobe-like, paired locomotory organs of annelids, that project laterally from the body segments.

Question 13.
What are comb plates?
Answer:
Comb plates are eight equidistant cilliary plates, present along the meridional line of the body of the members of Ctenophora to help in locomotion.

Question 14.
Members of which phylum is popularly called ‘comb jelly’?
Answer:
Members of phylum Ctenophora are popularly known as ‘comb jelly’.

Question .
Animals under which phylum possess cnidoblast cells?
Answer:
Animals under phylum Cnidaria possess cnidoblast cells.

Question 16.
Members of which phylum have unsegmented body covered with thick cuticle?
Answer:
Members of phylum Nematoda have unsegmented body, covered with thick cuticle.

Question 17.
Members of which phylum have segmented body covered with thick and rigid cuticle?
Answer:
Members of phylum Arthropoda have segmented body, covered with thick and rigid cuticle.

Question 18.
Members of which phylum have metamerically segmented body covered with elastic cuticle?
Answer:
Members of phylum Annelida have metamerically segmented body covered with elastic cuticle.

Question 19.
What is metameric segmentation?
Answer: The repetition of organs and tissues at intervals along the length of the body of an animal, thus dividing the body into a linear series of similar parts or segments, is called metameric segmentation.

Question 20.
Name two phyla whose members show metameric segmentation?
Answer:
Metameric segmentation is seen in the members of Annelida and Arthropoda.

Question 21.
Which group of animals use malpighian tubules for excretion?
Answer:
Members of the class Insecta, under phylum Arthropoda, use malpighian tubules as excretory organs.

Question 22.
Which group of animals use coxal gland for excretion?
Answer:
Scorpions, under class Arachnida of phylum Arthropoda, use coxal gland for excretion.

Question 23.
Which group of animals perform excretion by green gland?
Answer:
Prawns, under class Crustacea of phylum Arthropoda, perform excretion by green gland.

Question 24.
Which group of animals perform respiration by ctenidia?
Answer:
Aquatic snails and mussels, under phylum Mollusca, perform respiration by ctenidia.

Question 25.
Animals under which phylum possess canal system in their body?
Answer:
Animals under phylum Porifera possess canal system in their body.

Question 26.
Animals under which phylum perform locomotion by tube feet?
Answer:
Animals under phylum Echinodermata perform locomotion by tube feet.

Question 27.
Animals under which two classes possess four-chambered heart?
Answer:
Animals under class Aves and Mammalia, possess four-chambered heart.

Question 28.
Which group of vertebrates do not possess teeth?
Answer:
Birds do not possess teeth.

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

Question 1.
What are diploblastic animals?
Answer:
Those animals, whose body consists of two germinal layers, i.e. ectoderm and endoderm, are known as diploblastic animals. Example – Hydra etc.

Question 2.
What are triploblastic animals?
Answer:
Those animals, whose body consists of three germinal layers, i.e. ectoderm, mesoderm and endoderm, are known as triploblastic animals. Example -Tapeworms, earthworms etc.

Question 3.
What is meant by bilaterally symmetrical animals?
Answer:
The animals, which when divided once along the central axis gives two similar halves, are called bilaterally symmetrical animals. Example – Cockroach, human etc

Question 4.
What is meant by radially symmetrical animals?
Answer:
The animals, which when divided in any plane along the central axis gives rise to unlimited number of identical halves, are called radially symmetrical animals. Example – Starfish etc.

Question 5.
What is meant by asymmetrical animals?
Answer:
The animals, which when divided along any plane of the body, does not give rise to equal halves, are called asymmetrical animals. Example-Amoeba, molluscs etc.

Question 6.
What is spongocoel?
Answer:
The single, large central body cavity of the poriferan is called spongocoel. Water enters this cavity through several tiny pores called ostia and exits through a large opening called osculum.

Question 7.
What is meant by canal system?
Answer:
The animals under phylum Porifera have numerous pores all over the body. Through these pores water enters into the body and flows in all direction through a network of fine canals. This is called canal system.

Question 8.
What are ostia and osculum?
Answer:
Ostia: The animals under phylum Porifera possess numerous small pores all over their body which allow water to enter the body. These tiny pores are called ostia.

Osculum: The body cavity of the poriferans opens outside through a narrow circular opening, situated at the free end of their body. This opening is called osculum.

Question 9.
What is mesenchyme?
Answer:
Mesenchyme or mesohyl is a jelly-like layer with a few scattered cells and collagen fibres, present in between the two layers of cells of the body of the members of phylum Porifera and Ctenophora.

Question 10.
What is mesoglea?
Answer:
Mesoglea is a completely non-cellular jellylike layer, typically seen in between ectoderm and endoderm layer of the animals under phylum Cnidaria.

Question 11.
What is cnidoblast cell?
Answer:
Cnidoblast cell is a typical explosive epidermal cell, present in numbers on the tentacles of cnidarians. These cells carry huge secretory organelle, called nematocyst, which injects strong neurotoxin into the body of the preys and attackers.

Question 12.
What is nematocyst?
Answer:
Nematocyst is a typical stinging cell, present in the cnidoblast of cnidarians. This is a vesicle with a hairlike sensory process ejecting, called cnidocil, which discharges strong paralysing material to the preys and attackers.

Question 13.
What is gastrovascular cavity or coelenteron?
Answer:
The central tubular body cavity of cnidarian is called gastro vascular cavity or coelenteron. This cavity functions as both oral cavity as well as digestive cavity. It plays an important role in the digestion process of cnidarians.

Question 14.
What are collobiast cells or lasso cells?
Answer:
Colloblast cells or lasso cells are a kind of adhesive cells, present typically on the tentacles of the members of phylum Ctenophora. These cells are used to capture prey during predation.

Question 15.
What is metamere or somite?
Answer:
The body of annelids are transversely divisible into a series of several similar ring-like segments. These are called somites or metameres.

Question 16.
What is cephalothorax?
Answer:
The body of the members of phylum Arthropoda is segmented into head, thorax and abdomen. But certain crustaceans, such as prawn, crab, lobster etc. have their head fused with thorax. This typical structure is called cephalothorax.

Question 17.
What is mantle?
Answer:
The soft visceral organs of all molluscs remain covered with a typical muscular membrane. This is called mantle. In shelled molluscs, mantle remains just beneath the shell and secrete calcium carbonate and conchiolin, that creates the shell.

Question 18.
What is ambulacrum?
Answer:
Ambulacrum is one of the numerous equidistant radial bands, present medially along the oral side of an arm of echinoderms. It is an elongated area along which numerous tube feet protrude in two rows.

Question 19.
What is water-vascular system?
Answer:
In echinoderms, one ring canal and five sets of radial canals with their branches, connect with numerous tube feet and constitute a well organised vascular system. Through this, water flows within their body and helps them in locomotion, respiration and food and waste transportation. This typical circulatory system is known as water-vascular system.

Question 20.
What is notochord?
Answer:
Notochord is a rod-shaped, cartilaginous, axial supporting structure, typically possessed by all embryonic and some adult chordates. It forms the primitive axis of embryo among the chordates. It is made up of cells derived from mesoderm.

Question 21.
What is nerve cord?
Answer:
Nerve cord is a tubular structure, situated longitudinally along the dorsal side of the notochord in chordates. This is ectodermal in origin and is composed of nerve cells. In vertebrates, the anterior bulbous portion of nerve cord forms the brain and the posterior tubular portion becomes the spinal cord.

Question 22.
What are pharyngeal gill slits?
Answer:
Pharyngeal gill slits are paired pores, situated laterally at two opposite sides of the pharynx of all embryonic and several adult chordates. These pores are equipped with well-vascularised structures (gills), which act as respiratory organs that help to breath in amniotic fluid.

Question 23.
What are Protozoa?
Answer:
All the unicellular, eukaryotic, microscopic organisms, which belong to the kingdom Protista, are called Protozoa. Example-Amoeba, Paramoecium etc.

Question 24.
What are Parazoa?
Answer:
The primitive type of multicellular organisms under kingdom Animalia, having no specific tissues, organs or organ systems, are called Parazoa. Example-Sponges.

Question 25.
What are Metazoa?
Answer:
All the multicellular organisms under kingdom Animalia, having well-differentiated tissues, organs and organ systems, in order to carry out various physiological activities, are called Metazoa. Example-Sea anemones, earthworms, fishes etc.

Question 26.
What is Porifera?
Answer:
The phylum under kingdom Animalia, whose members possess body, composed of two layers and numerous pores and complex canal system, but lack true tissues, is called Porifera. ExampleScypha, Sycon, Spongilla etc.

Question 27.
What is Cnidaria?
Answer:
The phylum under kingdom Animalia, whose members are the diploblastic animals having a central body cavity with a single opening and tentacles equipped with stinging cnidoblast cells, is called Cnidaria. Example-Aurelia aurita (jellyfish), Metridium sp. (sea anemone) etc.

Question 28.
What is Ctenophora?
Answer:
The phylum under kingdom Animalia, whose members are marine, diploblastic, acoelomate, bisexual, having biradially symmetrical body and eight equidistant comb-like meridional cilliary plates along the body surface, is called Ctenophora. Example-Hormiphora, Beroe etc.

Question 29.
What is Platyhelminthes?
Answer:
The phylum under kingdom Animalia, whose members are triploblastic, bilaterally symmetrical animals with acoelomate, dorsiventrally flat body is called Platyhelminthes. Example-Planaria (flatworm), Taenia (tapeworm), Fasciola (liver fluke) etc.

Question 30.
What is Nematoda or Nemathelminthes or Ascheiminthes?
Answer:
The phylum under kingdom Animalia, whose members are triploblastic, with unsegmented, tubular, pseudocoelomic and bilaterally symmetrical body is called Nematoda or Nemathelminthes or Aschelminthes. ExampleAscaris (round worm), Wuchereria (filarial worm) etc.

Question 31.
What is Annelida?
Answer:
The phylum under kingdom Animalia, whose members are triploblastic, having true coelome and body transversely segmented into a number of ring-shaped somites or metameres, is called Annelida. Example-Pheretima (earthworm), Hirudinaria (leech) etc.

Question 32.
What is Arthropoda?
Answer:
The phylum under kingdom Animalia, whose members are triploblastic, having bilaterally symmetrical body, covered with chitinous exoskeleton and paired jointed appendages, is called Arthropoda. Example-Palaemon (prawn), Periplaneta (cockroach) etc.

Question 33.
What is Mollusca?
Answer:
The phylum under kingdom Animalia, whose members are triploblastic, coelomate, asymmetric or bilaterally symmetrical, having soft, unsegmented body, with visceral organs covered by a typical muscular membrane named mantle and the entire body covered with hard calcareous shell, is called Mollusca. Example-Pila (apple snail), Achatina (garden snail) etc.

Question 34.
What is Echinodermata?
Answer:
The phylum under kingdom Animalia, whose members are triploblastic, coelomate, pentaradially symmetrical, with numerous spines or ossicles on skin and unique water-vascular system in the body, is called Echinodermata. Example-Asterias (starfish), Cucumaria (sea cucumber) etc.

Question 35.
What is Chordata? Give example.
Answer:
The phylum under kingdom Animalia, whose members are diploblastic, coelomate, bilaterally symmetrical, which, at any phase of their life cycle possess notochord, dorsal tubular nerve cord, pharyngeal gill-slits and a post anal tail, is called Chordata. Example-Shark, toad, lizards, birds, mammals, etc.

Question 36.
How many sub-phyla are there under phylum Chordata? Name them.
Answer:
There are three sub-phyla under phylum Chordata. They are-Urochordata, Cephalochordata and Vertebrata.

Question 37.
What is Protochordata?
Answer:
The animals under phylum Chordata, in which notochord is not replaced by vertebral column, are called protochordates. The group which consists of these animals, is called Protochordata. Members of the sub-phyla Urochordata and Cephalochordata belong to this group.

Question 38.
What is Hemichordata? Give example.
Answer:
The phylum under kingdom Animalia, whose members are triploblastic, coelomate, with worm-like body divisible into proboscis, collar and trunk, having a dorsal tubular nerve cord and a number of paired pharyngeal gill slits, is called Hemichordata. ExampleBalanoglossus, Saccoglossus etc.

Question 39.
What is Urochordata or Tunicata?
Answer:
The sub-phylum under phylum chordata, the body of whose members is covered with a thin and transparent coat or tunic and their larvae possess the notochord restricted at the tail region, is called Urochordata or Tunicata. ExampleAscidia, Doliolum, Salpa etc.

Question 40
What is Cephalochordata or Acrania?
Answer:
The sub-phylum under phylum Chordata whose members are free-swimming, marine, having small lanceolate body and a well developed notochord extending from head to tail, is called Cephalochordata or Acrania. ExampleBranchiostoma, Asymmetron etc.

Question 41.
What is Vertebrata?
Answer:
The members of phylum Chordata, which possess a cranium, vertebral column and a welldeveloped endoskeleton, are called vertebrates and the sub-phylum is called Vertebrata. Example-Fishes, toads, dogs etc.

Question 42.
What is Agnatha?
Answer:
The vertebrates, which have a mouth without jaws, belong to a superclass called Agnatha. Example-Petromyzon (lamprey) etc.

Question 43.
What is Cyclostomata?
Answer:
The vertebrates, which have a round, jawless suctorial mouth, cartilaginous endoskeleton and a single nostril, belong to the class Cyclostomata. Example-Myxine (hagfish).

Question 44.
What is Gnathostomata?
Answer:
The vertebrates, whose mouth is guarded by a pair of jaws, having bony endoskeleton and two external nostrils, belong to a super-class called Gnathostomata. Example-Sharks, toads, mammals etc.

Question 45.
What is Chondrichthyes or Elasmobranchii?
Answer:
The class under kingdom Animalia, which includes jawed vertebrates, having cartilaginous endoskeleton, placoid scales on skin, mouth at the ventral side of the head and heterocercal or unevenly lobbed tail fin, is called Chondrichthyes or Elasmobranchii. Example-Scoliodon (shark), Dasyatis (stingray).

Question 46
What is Osteichthyes or Teleostomi?
Answer:
Osteichthyes or Teleostomi is a class under kingdom Animalia, which includes jawed vertebrates, having bony endoskeleton, paired gills covered with operculum, anteriorly placed mouth and homocercal or evenly lobbed tail fin. Example-Labeo rohita (rohu fish), Catla catla (catla fish) etc.

Question 47.
What is Amphibia?
Answer:
Amphibia is a class under kingdom Animalia, which includes cold-blooded vertebrates, with bony endoskeleton, which perform reproduction, spend larval life in aquatic environment but on maturity spend most of their life on land, have their body covered with naked, moist glandular skin and have a three-chambered heart. Example-Duttaphrynus (toad), Rana (frog) etc.

Question 48.
What is Reptilia?
Answer:
Reptilia is a class under kingdom Animalia, which includes cold-blooded vertebrates, whose body is covered with dry epidermal scales or scutes, have pentadactyl limbs with clawed digits (exception snakes) and perform respiration with the help of lungs. Example-Calotes (garden lizard), Naja (cobra) etc.

Question 49.
What is Aves?
Answer:
Aves is a class under kingdom Animalia, which includes warm-blooded vertebrates, whose body is covered with feathers, jaws modified into beaks, fore limbs modified into wings and have four-chambered heart. Example-Corvus (crow), Pavo (peacock) etc.

Question 50.
What is Mammalia?
Answer:
Mammalia is a class under kingdom Animalia, which includes warm-blooded vertebrates having body hair, a pair of pinnae at two sides of the head and the female members possess mammary glands to feed milk to their offsprings. Example-Canis (dog), Felis (cat) etc.

Question 51.
Which animals are called poikilothermic or cold-blooded animals?
Answer:
Body temperature of certain animals increases and decreases according to the rise and drop of environmental temperature. These animals are called poikilothermic or cold-blooded animals. Example-Fishes, amphibians and reptiles.

Question 52.
Which animals are called endothermic or homoeothermic or warm-blooded animals? Give examples.
Answer:
Body temperature of certain animals does not fluctuate with the change in environmental temperature. These animals are called endothermic or homoeothermic or warm blooded animals. Example-Birds and mammals.

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

Question 1.
Schematically represent the classification of animal kingdom with one example each.
Answer:
Schematic representation of the classification of animal kingdom.

Question 2.
Mention the identifying features of phylum Porifera. Give two examples with scientific names.
Answer:
Identifying features of phylum Porifera
The identifying features of phylum Porifera are as follows-

• Body is multicellular, without well-developed tissue system.
• Body is arranged in two layers and jelly-like mesenchyme is present in between these two layers.
• Exoskeleton is hard and rigid, made up of calcium or silicon-rich cells, called spongin fibres or spicules.
• One large aperture, called osculum is present at the upper end of the body. There are numerous tiny pores, called ostia, spreaded all over their body.
• Water flows continuously in the body through pores, interconnected canals and chambers.

Example with scientific names:
Two examples of the members of phylum Porifera are Neptune’s cup (Poterion neptuni) and freshwater sponge (Spongilla lacustris).

Question 3.
Mention the identifying features of phylum Cnidaria. Give two examples with scientific names.
Answer:
Identifying features of phylum Cnidaria

The identifying features of phylum Cnidaria are as follows-

• Members of this group live in water.
• They have a soft diploblastic body, made up of ectoderm and endoderm. In between these two layers, an acellular jelly-like mesoglea is present.
• Body radially or biradially symmetrical, has a gastrovascular cavity called coelenteron. This cavity has a single opening that is surrounded by tentacles.
• Typical stinging cells, called cnidoblasts, are present on the tentacles, equipped with a special stinging structure called nematocyst, which is used to capture prey and for self-defence.

Example with scientific names:
Two examples of the members of phylum Cnidaria are hydra (Hydra viritlis) and jellyfish (Aurelia aurita).

Question 4
Mention the identifying features of phylum Ctenophora. Give two examples.
Answer:
Identifying features of phylum Ctenophora

The identifying features of phylum Ctenophora are as follows-

• Body is diploblastic, made up of ectoderm and endoderm and bi-radially symmetrical. In between ectoderm and endoderm, a layer of jelly-like substance called mesenchyme is present.
• Body distinguishable into oral and aboral ends. The aboral end consists of a sensory structure, called statocyst.
• Eight quidistant longitudinal ciliary plates or comb plates are present on the body that help in locomotion.
• Typical adhesive cells, called colloblast cells or lasso cells are present in the tentacles. These colloblast cells help in capturing prey during predation.

Example of Ctenophores
Two examples of the members of phylum Ctenophora are Hormiphora plumosa and Beroe forskalii.

Question 5.
Mention the identifying features of phylum Platyhelininthes. Give two examples with scientific names.
Answer:
Identifying features of phylum Platyheiminthes

The identifying features of phylum Platyhelminthes are as follows-

• Body is dorsiventrally flat, so are called flatworms and externally covered by syncytial membrane. Their body is bilaterally symmetrical.
• Body wall is composed of three germinal layers-ectoderm, mesoderm and endoderm. Hence, they are triploblastic.
• Body cavity or coelom is absent. Body consists of a distinct head region and a prominent sucker at the mouth.
• Except reproductive system, other organ systems are not well developed. Excretion occurs by flame cells or protonephridia.
• All members of this group are hermaphrodite, i.e., bisexual.
• They may be free-living or parasitic.

Example with scientific names
Two examples of the members of phylum Platyhelminthes are tapeworm (Taenia solium) and liver fluke (Fasciola hepatica).

Question 6.
Mention the identifying features of phylum Nemathelminthes or Nematoda. Give two examples with scientific names.
Answer:
Identifying features of phylum Nemathelminthes or Nematoda

The identifying features of the phylum Nemathelminthes are as follows-

• Body is bilaterally symmetrical, long and cylindrical.
• They are triploblastic, i.e., body wall composed of three germinal layers-ectoderm, mesoderm and endoderm.
• Body is unsegmented and is covered with thick cuticle.
• A very narrow, fluid-filled body cavity or pseudocoelom is present. Organ systems are poorly developed.
• Members of this group are unisexual, i.e., with separate male and female individuals.

Example with scientific names:
Two examples of the members of phylum Nematoda are filarial worm (Wuchereria bancrofti) and hookworm (Ancylostoma duodenale).

Question 7.
Mention the identifying features of phylum Annelida. Give two examples with scientific names.
Answer:
Identifying features of phylum Annelida

The identifying features of phylum Annelida are as follows

• Body is composed of several ring-like segments called metameres or annuli. Hence, they are named annelids.
• Body is bilaterally symmetrical and triploblastic, i.e.body wall divided into ectoderm, mesoderm and endoderm.
• True body cavity or coelom is present. Organs are well differentiated.
• The annelids use setae and parapodia for locomotion.
• Each body segment bears a pair of nephridia, which act as excretory organs.

Example with scientific names
Two examples of the members of phylum Annelida are earthworm (Pheretima posthuma) and sand worm (Nereis virens).

Question 8.
Mention the identifying features of phylum Arthropoda. Give two examples with scientific names.
Answer:
Identifying features of phylum Arthropoda

The identifying features of phylum Arthropoda are as follows –

• Body is bilaterally symmetrical and externally segmented.
• The organisms have paired jointed appendages for locomotion.
• Body wall composed of ectoderm, mesoderm and endoderm, i.e., they are triploblastic.
• Body generally differentiated into head, thorax and abdomen. In some cases, head and thorax fuse together, forming cephalothorax.
• Thick and rigid exoskeleton is present, which is made up of chitin.
• Circulatory system is open, i.e., blood flows in coelomic body cavity, which is called haemocoel.

Example with scientific names
Two examples of the members of phylum Arthropoda are cockroach (Periplaneta americana), housefly (Musca domestica).

Question 9.
Mention the identifying features of phylum Mollusca. Give two examples with scientific names.
Answer:
Identifying features of phylum Mollusca

The identifying features of phylum Mollusca are as follows-

• Body is soft, bilaterally symmetrical, unsegmented and muscular.
• Body of most of the members are enclosed within a hard caicareous shell, made up of calcium carbonate.
• Visceral mass remains covered with a muscular membrane, called mantle.
• They have reduced body cavity and open circulatory system.
• Body bears kidney-like organs for excretion. They perform respiration by a single or a pair of gill-like organs present within pulmonary sac or by means of ctenidia.
• A special apparatus, called radula, is present at the base of mouth. It bears rows of chitinous teeth, which help in scrapping or cutting food.
• Creeping members of this phylum have muscular foot and swimming members have undulating membrane for lacomotion.

Example with scientific names
Two examples of the members of phylum Mollusca are garden snail (Achatina fulica) and squid (Loligo vulgaris).

Question 10.
Mention the identifying features of phylum Echinodermata. Give two examples with scientific names.
Answer:
Identifying features of phylum Echinodermata

The identifying features of phylum Echinodermata are as follows-

• Body is triploblastic, i.e., body wall made up of ectoderm, mesoderm and endoderm and body is pentaradially symmetrical.
• Body differentiated into oral and aboral surfaces.
• Body surface bears numerous spines and their endoskeleton consists of hard, calcareous ossicles, that are made up of calcium carbonate.
• Oral surface of the body has five radial ambulacra with distinct ambulacral grooves.
• They have a proper coelomic cavity and wellorganised water-vascular system that is used for circulation.
• Numerous tube feet are present on either side of the ambulacral grooves, which help in locomotion.

Example with scientific names
Two examples of the members of phylum Echinodermata are starfish (Asterias rubens), and sea cucumber (Cucumaria frondosa).

Question 11.
Mention the Identifying features of phylum Hemichordata. Give two examples.
Answer:
Identifying features of phylum Hemichordata

The identifying features of phylum Hemichordata are as follows-

• Members of this group are Balanoglossus soft bodied, coelomate, worm-like, marine animals.
• Body is divided into proboscis, collar and trunk.
• Paired pharyngeal gill slits are present in the trunk.
• They are devoid of endoskeleton and notochord.
• The nerve cord is dorsally placed, which is rod-like in most members, but hollow in few.
• A small diverticulum is present near oesophagus, called stomochord, which is a flexible hollow tube that helps to communicate with oral cavity.
• They possess an independent larval stage, named tornaria larva, at initial stage of their life cycle.

Examples of hemichordates
Two examples of hemichordates are Balanoglossus gigas and Saccoglossus sp.

Question 12.
Mention the Identifying features of phylum Chordata. Give two examples.
Answer:
Identifying features of phylum Chordata
The identifying features of phylum Chordata are as follows-

• A tubular nerve cord is present at dorsal side of the body.
• Below the dorsal tubular nerve cord, the animals possess a rod-shaped supporting structure, called notochord. It remains throughout their life or at least during embryonic stage.
• Paired pharyngeal gill slits are present throughout or, at certain period of their life cycle.
• All members have a post anal tail or at least some remains of it.
• The members under this phylum possess closed circulatory system.

Example of chordates
Two examples of chordates are Branchiostoma lanceolatum and Homo sapiens sapiens.

Question 13.
Distinguish between chordates and non-chordates.
Answer:
Differences between chordates and non-chordates

Features	Chordates	Non-chordates
1. Notochord	Present throughout or at certain stage of life cycle	Completely absent
2. Nerve cord	Tubular structure, present at the dorsal side of the body	Thread-like structure, present at the ventral side of the body
3. Vertebral column	Present in most members	Completely absent
4. Skull	Present and made up of bones and cartilages	Absent
5. Circulatory system	Closed circulatory system with arteries, veins and capillaries	Open circulatory system with arteries and veins, but capillaries are absent

Question 14.
Mention the identifying features of sub-phylum Urochordata. Give two examples.
Answer:
Identifying features of sub-phylum Urochordata

The identifying features of sub-phylum Urochordata are as follows

• Sac-like soft body of the members is covered by a membrane called tunic.
• Paired pharyngeal gill slits are present in adults. The pharyngeal region is surrounded by a membrane-bound cavity, called atrium.
• Notochord and nerve chord present during larval stage.
• Free-swimming tadpole stage is observed during the life cycle of the organisms. They undergo retrogressive metamorphosis by losing notochord and nerve cord on maturity.

Example of urochordates
Two examples of urochordates are Ascidia mentula and Doliolum denticulatum.

Question 15.
Mention the identifying features of sub-phylum Cephalochordata. Give two examples.
Answer:
Identifying features of sub-phylum Cephalochordata

The identifying features of sub-phylum Cephalochordata are as follows-

• This sub-phylum includes small fish-like animals with indistinct head. Body is bilaterally symmetrical, triploblastic and with coelomic body cavity.
• Notochord is well developed, which contracts and expands and extends from head to tail.
• Dorsal tubular nerve cord and paired pharyngeal gill slits are present.
• A typical ciliated groove, called endostyle, is present at the ventral wall of pharynx.
• Oral opening is laterally guarded by two flap-like structures, called oral hoods, with ciliated edge.

Example of cephalochordates
Two examples of cephalochordates are Branchiostoma lanceolatum and Asymmetron inferum.

Question 16
Mention the identifying features of sub-phylum Vertebrata or Craniata. Give two examples with scientific names.
Answer:
Identifying features of sub-phylum Vertebrata or Craniata
The identifying features of sub-phylum Vertebrata are as follows-

• Members of this group are bilaterally symmetrical, triploblastic and with coelomic body cavity.
• Notochord is replaced by a true vertebral column. Body possesses internal skeleton, made up of bones and cartilage.
• Brain remains protected inside cranium.
• Dorsal tubular nerve cord emerges from base of the brain and passes through the vertebral column.
• Two pairs of joint limbs present, which help in locomotion.

Example with scientific names
Two examples of the members of sub-phylum Vertebrata are rohu fish (Labeo rohita) and cat (Felis domesticus).

Question 17.
Mention the identifying features of super-class Agnatha with two examples. Mention the identifying features of super-class Gnathostomata with two examples.
Answer:
Identifying features of super-class Agnatha

The identifying features of super-class Agnatha are as follows-

• Body is elongated, with cartilaginous endoskeleton.
• Suctorial mouth is present without any jaw.
• Only a single external nostril is present.
• A number of pharyngeal gill slits are present along the two opposite sides of the body.

Example – Two examples of the members of super-class Agnatha are lamprey (Petromyzon marinus) and hagfish (Myxine glutinosa).

Identifying features of super-class Gnathostomata
The identifying features of super-class Gnathostomata are as follows-

• The mouth of the animals under this super-class is guarded by a pair of jaws.
• They have two external nostrils.
• Endoskeleton is made up of either bone or cartilage

Example- Two examples of the members of super-class Gnathostomata are shark (Scoliodon sorrakowah) and crocodile (Crocodylus porosus).

Question 18.
Mention the identifying features of class Cyclostomata. Give two examples with scientific names.
Answer:
Identifying features of class Cyclostomata

Cyclostomata is the only class under super-class Agnatha. Its characteristic features are as follows:

• The animals under this class are cold-blooded. Mouth has no jaw. Oral opening has a circular sucker, which is guarded by papillae or small tentacles.
• One medial external nostril is present.
• Body is long, cylindrical, tapering towards the tail.
• The members do not have distinct stomach or any appendages.
• Fertilisation, as well as development, both are external.
• They possess unpaired fins and do not have body scales.
• Skull and endoskeleton, both are cartilaginous.
• Heart is two-chambered, 6-14 pairs of gills present in sac.

Example with scientific names
Two examples of the members of class Cyclostomata are lamprey (Petromyzon marinus) and hagfish (Myxine glutinosa).

Question 19
Mention the identifying features of class Chondrichthyes. Give two examples with scientific names.
Answer:
Identifying features of class Chondrichthyes

The identifying features of class Chondrichthyes are as follows-

• The animals under this class Shark are cold-blooded and bilaterally symmetrical.
• Members of this group have streamlined body and cartilaginous endoskeleton.
• Body is covered with minute placoid scales.
• About 5-7 pairs of gill slits present at the lateral side of the body and are without operculum.
• Mouth present at the ventral side of the head.
• Body has paired and unpaired fins, with fin rays. Air bladder typically absent.
• They possess heterocercal tail, i.e., with two unequal lobes. Anal fins of male form claspers, which help to deposit sperms.

Example with scientific names
Two examples of the members of class Chondrichthyes are shark (Scoliodon sorrakowah) and sawfish (Anoxypristis cuspidata).

Question 20.
Mention the identifying features of class Osteichthyes. Give two examples with scientific names.
Answer:
Identifying features of class Osteichthyes

The identifying features of the class Osteichthyes are as follows

• The animals under this class are bilaterally symmetrical and are cold-blooded animals.
• They have streamlined body covered with ganoid, cycloid or ctenoid scales.
• Their endoskeleton and fin rays are made up of bones.
• Four pairs of gills present in gill chambers on either side of head. Each gill Rohu fish chamber remains covered with a bony plate, called operculum.
• Five pairs of gill arches and one pair of external gill slits present.
• They have paired or unpaired fins, with bony fin rays.
• Tail fin is homocercal with identical lobes.
• A typical swim bladder is present in the body.

Example with scientific names
Two examples of the members of class Osteichthyes are rohu fish (Labeo rohita) and catla fish (Catla catla).

Question 21.
Mention the identifying features of class Amphibia. Give two examples with scientific names.
Answer:
Identifying features of class Amphibia

The identifying features of class Amphibia are as follows-

• The animals belonging to this class are cold-blooded animals.
• Body is differentiated into head and trunk, without distinct neck.
• Body is covered with naked, moist, glandular skin without scales.
• Larvae live in water and respire with external gills. Adults are terrestrial and respire with lungs, but apart from this, skin and buccopharyngeal cavity also participate in respiration.
• Forelimbs have four and hind limbs have five digits each. The digits are without claws.
• They have three-chambered heart, with two auricles and one ventricle.

Example with scientific names
Two examples of the members of class Amphibia are toad (Duttaphrynus melanostictus) and frog (Rana tigrina).

Question 22.
Mention the identifying features of class Reptilia. Give two examples with scientific names.
Answer:
Identifying features of class Reptilia

The identifying features of class Reptilia are as follows –

• The animals under this class are cold-blooded animals.
• Body is covered with large dermal plates or dry epidermal scales, called scutes.
• They perform locomotion by crawling.
• Each of the fore and hind limbs have five clawed digits. (exception-snakes are limbless).
• Body is distinctly divisible into head, neck, trunk and tail. Cloaca is present transversely near the base of the tail.
• They generally have three chambered heart, with two auricles and a partially divided ventricle (exception – crocodile has four-chambered heart with completely divided ventricle).

Example with scientific names
Two examples of the members of class Reptilia are garden lizard (Calotes versicolor) and crocodile (Crocodylus porosus).

Question 23
Mention the identifying features of class Aves. Give two examples with scientific names.
Answer:
Identifying features of class Aves

The identifying features of the class Aves are as follows-

• The animals belonging this class are warm-blooded animals.
• Body is spindle-shaped and covered with feathers.
• Forelimbs are modified into wings.
• Their bones are hollow due to the presence of air cavities. This helps to reduce their weight and help in flying.
• Besides lungs, they have 9 air sacs, which help in flight.
• Urinary bladder, rectum and right ovary absent in order to reduce body weight.
• Teeth completely absent and jaws are modified into beaks.
• They have four-chambered heart with two auricles and two ventricles.

Example with scientific names
Two examples of the members of class Aves are crow (Corvus splendens) and pigeon (Columba livia).

Question 24
Mention the identifying features of class Mammatia. Give two examples with scientific names.
Answer:
Identifying features of class Mammalia

The identifying features of class Mammalia are as follows-

• The animals under this class are warm-blooded animals and their bodies are bilaterally symmetrical.
• Body is covered with hair. Sweat and sebaceous glands are present in the skin.
• The female members of this group have milk-producing mammary glands, for nourishing their young ones.
• A pair of external ears or pinnae is present on either side of the head.
• Respiration occurs by a pair of lungs.
• They have two pairs of limbs, used for locomotion, digging, holding or feeding.
• They are viviparous animals, i.e., give birth to young ones.
• Heart is four-chambered with two auricles and two ventricles and has left aortic arch.

Example with scientific names
Two examples of the members of class Mammalia are man (Homo sapiens sapiens) and deer (Axis axis).

Detailed explanations in West Bengal Board Class 9 Life Science Book Solutions Chapter 1.3C Classification of Kingdom Plantae offer valuable context and analysis.

WBBSE Class 9 Science Chapter 1.3C Question Answer – Classification of Kingdom Plantae

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

Question 1.
Members of which group of plants are not divisible into roots, stems and leaves?
Answer:
Members of thallophyta are not divisible into roots, stems and leaves.

Question 2.
Name an alga which has spirally coiled chloroplast In its cells.
Answer:
Spirogyra is an alga, has spirally coiled chloroplast in its cells.

Question 3.
Name a filamentous alga having prokaryotic cells.
Answer:
Nostoc is a filamentous alga, having prokaryotic cells.

Question 4.
Name a colony-forming alga.
Answer:
Volvox is a colony-forming alga.

Question 5.
Name a unicellular alga, which is now treated as a protist.
Answer:
Chlamydomonas is a unicellular alga, which is now treated as a protist.

Question 6.
What is the fine, branched, colourless, filamentous structure of a fungus called?
Answer:
The fine, branched, colourless, filamentous structure of a fungus is called mycelium.

Question 7.
What are the filaments of a fungal mycelium known as?
Answer:
The filaments of a fungal mycelium are known as hyphae.

Question 8.
What is the name of the fungal component of a lichen?
Answer:
The fungal component of a lichen is called mycobiont.

Question 9.
What is the name of the algal component of a lichen?
Answer:
The algal component of a lichen is called phycobiont.

Question 10.
Which type of bryophytes form velvety thallus on moist soil?
Answer:
Liverworts form velvety thallus on moist soil.

Question 11.
What is the name of the erect portion of moss?
Answer:
The erect portion of moss is called gametophore.

Question 12.
What is the name of the stem-like portion of a moss?
Answer:
The stem-like portion of a moss is called caulid.

Question 13.
What is the name of the fine root-like structure of a moss?
Answer:
The fine root-like structure of a moss is called rhizoid.

Question 14.
What does the rhizoid of a moss do?
Answer:
Rhizoid of a moss absorbs water from the soil and affix the plant body to the soil.

Question 15.
Which type of plants possess leaves, stems and roots but do not develop flower and fruit?
Answer:
Ferns possess leaves, stems and roots but do not develop flower and fruit.

Question 16.
Which plants possess ramenta on their stems and the petioles of leaves?
Answer:
Ferns posses ramenta on their stems and the petioles of leaves.

Question 17.
Name a plant in which aerial part is comprised of pileus and stipe.
Answer:
Aerial part of Agaricus is comprised of pileus and stipe.

Question 18.
What are the wart-like structures below the leaflets of Dryopteris called ?
Answer:
The wart-like structures below the leaflets of Dryopteris are called sori.

Question 19.
Members of which division of plants are known as amphibious plants?
Answer:
Plants under division bryophyta are known as amphibious plants.

Question 20.
In which division of plants, seeds develop without formation of fruits?
Answer:
In gymnosperms, seeds develop without formation of fruits.

Question 21.
Which type of plant body is seen amongst ferns?
Answer:
Sporophytic plant body is seen amongst ferns.

Question 22.
What is the name of the symbiotic association of fungi and the roots of higher vascular plants?
Answer:
The symbiotic association of fungi and the roots of higher vascular plants is known as mycorrhiza.

Question 23.
Which division of non-flowering plants possess vascular system?
Answer:
Plants under division pteridophyta are nonflowering plants, which possess vascular system.

Question 24.
In which group of plants usually many embryos are formed in a single seed?
Answer:
In gymnosperms, usually many embryos are formed in a single seed.

Question 25.
Which group of plants always show tap root system?
Answer:
Dicotyledonous plants always show tap root system.

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

Question 1.
What is meant by algae?
Answer:
The simplest form of autotrophic, aquatic plants, with thallophytic body, made up of mainly eukaryotic cells, without any tissue system and having unicellular sex organs, are called algae. Example-Spirogyra sp., Chara sp.

Question 2.
What is thallophyta?
Answer:
Thallophyta is a plant group, that includes those plants having flat thallus-like body, which are not divisible into root, stem and leaf. Example-Algae.

Question 3.
What are bryophytes?
Answer:
Bryophytes are simple non-flowering plants without true roots, stems, leaves and vascular tissues. They grow in moist soil but perform fertilisation in water and maintain gametophytic generation throughout the major part of their life cycle. Example-Pogonatum sp., Sphagnum sp.

Question 4.
What are pteridophytes?
Answer:
Pteridophytes are terrestrial non-flowering plants having true roots, stems, leaves and vascular tissues. They maintain sporophytic generation throughout the major part of their life cycle.
Example — Marsilea sp., Selaginella sp.

Question 5.
What are gymnospenns?
Answer:
The group of plants, in which no fruit is produced, so that the seeds remain exposed and usually many embryos form inside a seed, are called gymnosperms or naked-seeded plants, where endosperm forms before fertilisation. Example — Cycas sp., Pinas sp.

Question 6.
What are anglesperms?
Answer:
The flowering plants, in which fruits develop from flowers and seeds remain within the fruits, are called angiosperms. Here, the endosperm forms after fertilisation. Example — Solanum tuberosum (potato), Malus domestica (apple).

Question 7.
What is meant by dicotyledonous plants?
Answer:
The angiospermic plants, in which seeds have two cotyledons, show tap root system and have reticulate venation in leaves, are called dicotyledonous plants. Example-Mangifera indica (mango), Pisum sativum (pea).

Question 8.
What is meant by monocotyledonous plants?
Answer:
The angiospermic plants, in which seeds have only one cotyledon, show adventitious root system and have parallel venation in leaves, are called monocotyledonous plants. Example-Cocos nucifera (coconut), Triticum aestivum (wheat).

Question 9.
What are rhizoids?
Answer:
Rhizoids are branched, colourless, very fine thread-like structures growing from the base of the gametophores or the ventral side of the thallus of mosses, which help to absorb water and minerals from soil and affix the plant with the subtratum.

Question 10.
What is a gametophore?
Answer:
The gametophore is a structure, present in the gametophytic generation of mosses and ferns, which bears the male and female sex organs, known as antheridium and archegonium respectively.

Question 11.
What are ramenta? What is the function of ramenta?
Answer:
(i) Ramenta: Some species of ferns have several thin, brown scale or hair-like projections upon the young shoots and the petioles of leaves. These are called ramenta.
(ii) Function: Ramenta prevent the ferns from drying out by reducing the rate of transpiration in arid condition.

Question 12.
What is circinate vernation?
Answer:
The manner in which immature leaves of ferns are tightly curled so that the tender growing tip of the frond remains protected within a coiled structure, is called circinate vernation. This is commonly seen in Dryopteris sp.

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

Question 1.
Classify plant kingdoms with the help of a chart and example.
Answer:
Classification of plant kingdom with examples

Question 2.
Mention the similarities between algae and fungi. Discuss their differences.
Answer:
Similarities between algae and fungi
The similarities between algae and fungi are as follows-

• Both are eukaryotic, unicellular or multicellular.
• Both forms are thallophytic, that is their body is not differentiated into roots, stems and leaves.
• Both algae and fungi have distinct cell wall outside their cells.
• Both algae and fungi are devoid of vascular tissues.

Differences between algae and fungi

Features	Algae	Fungi
1. Habitat	Mostly aquatic, few grow on moist soil	Mostly terrestrial
2. Nutrition	Mostly autotrophic	All are heterotrophic, mostly saprophytic, some are parasitic
3. Photosynthetic pigments	Chlorophyll and other pigments	Photosynthetic pigments absent
4. Main component of cell wall	Main component is cellulose	Main component is chitin
5. Stored food	Stored food is starch and other polysaccharides	Stored food is glycogen
6. Vacuole	Centrally large and few vacuoles present	Small and many vacuoles present

Question 3.
Mention the similarities between bryophytes and pteridophytes. Discuss the differences between them.
Answer:
Similarities between bryophytes and pteridophytes
The similarities between bryophytes and pteridophytes are as follows-

• Both bryophytes and pteridophytes are non-flowering plants.
• Both show distinct gametophytic and sporophytic generations in their respective life cycles.
• Both require water for fertilisation.
• Both carry out asexual reproduction by means of spores.
• The structure of male and female gametangia are alike in both bryophytes and pteridophytes. Reproductive cells are externally covered by sterile cells.

Differences between bryophytes and pteridophytes

Features	Bryophytes	Pteridophytes
1. Body	Body differentiated into stem and leaves, true roots absent	Body differentiated into true roots, stem and leaves
2. Main plant type	Main plant type is gametophytic	Main plant type is sporophytic
3. Vascular tissue	True vascular tissues are absent	Xylem and phloem are present
4. Habitat	Moist soil and rocky surfaces	Cool, shady but dry surfaces
5. Roots	True root system absent, root-like rhizoids are present	True root system is present
6. Sperms	Sperms biflagellate	Sperms multi flagellate

Question 4.
Mention the similarities between gymnosperms and angiosperms. Write the differences between them.
Answer:
Similarities between gymnosperms and angiosperms
Similarities between gymnosperms and angiosperms are as follows—

• Both gymnosperms and angiosperms have their bodies differentiated into true roots, stems and leaves.
• Both the types of plants develop seeds after fertilisation.
• In both forms, the ovules remain covered by integument.
• Both gymnosperms and angiosperms have well-organised vascular bundle.

Differences between gymnosperms and angiosperms:

Features	Gymnosperms		Angiosperms
1. Nature	Perennial and evergreen		Annual, biennial or perennial, evergreen or deciduous
2. Vascular tissue	Xylem and phloem are devoid of trachea and companion cells respectively		We developed xylem and phloem present
3. Flower and fruit	Flowers lack ovary, therefore no fruit formation occurs		Flowers have ovary, which matures into fruit
4. Seed	Seeds remain exposed		Seeds remain inside the fruit
5. Embryo	More than one embryo originates in ovule, but only one matures		Single embryo is formed in an ovule
6. Endosperm	Endosperm forms before fertilisation		Endosperm forms after fertilisation

Question 5.
Mention the differences between monocotyledonous and dicotyledonous plants. Write the scientific names of two monocot and two dicot plants.
Differences between monocotyledonous and dicotyledonous plants
Answer:

1. Nature	Annual, mostly herbs, rarely shrubs and trees	Perennial, majority are trees, but several herbs and shrubs are also present
2. Cotyledons	Seed has single cotyledon	Seed has two cotyledons
3. Leaves	Isobilateral, with parallel venation	Dorsiventral, with reticulate venation
4. Stem	Generally unbranched and less woody	Well-branched and mostly woody
5. Root	Adventitious roots present	Taproot system present
6. Vascular bundle	Numerous and scattered vascular bundles in stem	Few vascular bundles in stem, arranged in circles or rings

Scientific name of monocot and dicot plants
The scientific names of two inonocot plants are Oryza sativa (rice) and Zea mays (maize) and the scientific names of two dicot plants are Mangifera indica (mango) and Pisum sativum (pea)

Question 6.
Mention the main characteristic features of algae, Give two examples.
Answer:
Characteristic features of algae

The main characteristic features of algae are as follows—

• Algae are unicellular or multicellular aquatic thallophytes.
• These are autotrophic, i.e. they can synthesise their own food within the body, due to the presence of chlorophyll.
• Algal cell wall is mainly composed of cellulose and pectin.
• Algal cells have variously shaped chloroplasts, which contain photosynthetic pigments and stored food like starch.
• Sub-cellular micro compartments, called pyrenoids, are present in the chloroplasts.
• Algae perform vegetative, asexual and sexual reproduction.

Examples of algae
Two examples of algae are Spirogyra maxima and Volvox globator.

Question 7.
Mention the main characteristic features of bryophytes. Give two examples. Characteristic features’ of bryophytes
Answer:
The main characteristic features of bryophytes are as follows:

• Bryophytes are green, photosynthetic and non-vascular plants.
• Plants are either thallus-like or have indistinguishable stem-like caulid, leaf-like phyllids and rhizoids in place of roots.
• The plant body of bryophytes is gametophytic.
• Sporophyte depends upon the gametophyte for survival.
• Both male and female reproductive organs are multicellular.
• Alternation of generation is distinct and unequal, where gametophytic generation dominates over the sporophytic generation.

Examples of bryophytes
Two examples of bryophytes are Riccia fluitans and Funaria hygrometrica.

Question 8.
Mention the main characteristic features of pteridophytes. Give two examples.
Answer:
Characteristic features of pteridophytes:

The main characteristic features of pteridophytes are as follows-

• Pteridophytes are muiticellular, non-flowering plants with vascular tissue system.
• Vascular system is composed of xylem and Marsilea minuta phloem.
• Vegetative body is differentiated into roots, stems and leaves.
• The independent plant body is sporophytic.
• Sporophylls or spore bearing leaves either arrange themselves to form cones or remain free as compound leaves.
• Alternation of generation is distinct and unequal, where sporophytic generation dominates over the gametophytic generation.

Examples of pteridophytes:
Two examples of pteridophytes are Dryopteris filix-mas and Marsilea minuta.

Question 9.
Mention the main characteristic features of gymnosperms. Give two examples.
Answer:
Characteristic features of gymnosperms:

The main characteristic features of gymnosperms are as follows-

• Gymnosperms are perennial sporophytic trees.
• Body differentiated into roots, stems and leaves.
• Leaves are of two types-dry brown scale leaves and green foliage leaves. Foliage leaves are either needle-like or compound.
• Vascular system present but xylem and phloem are devoid of trachea and companion cells respectively.
• Fruit absent, that is why seeds remain exposed or naked.
• Seeds bear more than one embryo, a feature typically known as polyembryony.
• In gymnosperms, endosperm develops before fertilisation.

Examples of gymnosperms:
Two examples of gymnosperms are Pinus roxburghii and Gnetum ula.

Question 10.
What is a sorus? What is cone or strobilus? Give the differences between cryptogams and phanerogams.
Answer:
Sorus
The small, kidney-shaped, wart-like structure which grows on the ventral surface of the leaflets of ferns, to hold the sporangia within it, is called sorus.

Cone or Strobilus
In most gymnosperms, a number of male or female reproductive organs or sporangia-bearing, scale-like structures arrange closely around a central axis to form a cone-shaped or oval structure. This is called cone or strobilus.

Differences between cryptogams and phanerogams:

Features	Cryptogams	Phanerogams
1. Seeds	Do not produce seeds	Produce seeds
2. Vascular system	May or may not be present	Always present
3. Need for water	External water serves as medium	External water is not required
4. Evolutionary status	These are primitive type	These are advanced type

Question 11.
Mention the main characteristic features of angiosperms. Give two examples.
Answer:
Characteristic features of angiosperms

The main characteristic features of angiosperms are as follows-

• Angiosperms are either herbs, shrubs or trees.
• Their life span varies from annual, biennial to perennial.
• Vascular tissue system is highly developed, composed of all components of xylem and phloem.
• Flowers develop ovary, which matures into fruit. Seeds remain protected inside the fruit.
• Seeds may have one or two cotyledons.
• In angiosperms, endosperm develops after fertilisation.

Examples of angiosperms
Two examples of angiosperms are Cocos nucifera and Mangifera indica.

Question 12.
Mention the main characteristic features of monocotyledonous plants. Give two examples.
Answer:
Characteristic features of monocotyledonous plants

The main characteristic features of monocotyledonous plants are as follows-

• Monocots are mostly herbs, a few are trees.
• Their life span varies from annual to perennial.
• Their seeds have a single cotyledon.
• Their roots are adventitious.
• Stems are unbranched and leaves are isobilateral with parallel venation.
• Fruit coat remains fixed with the seed coat.

Examples of monocotyledonous plants
Two examples of monocotyledonous plants are Oryza sativa and Zea mays.

Question 13.
Mention the main characteristic features of dicotyledonous plants. Give two examples.
Answer:
Characteristic features of dicotyledonous plants

The main characteristic features of dicotyledonous plants are as follows-

• Dicots are mostly trees, some are herbs and shrubs.
• Their life span varies from annual, biennial to perennial.
• Their seeds have two cotyledons.
• Well developed tap root system is present in these type of plants.
• Stems are branched and leaves are dorsiventral with reticulate venation.
• Fruit coat and seed coat remain separate.

Examples of dicotyledonous plants
Two examples of dicotyledonous plants are Artocarpus heterophyllus and Pisum sativum.

Detailed explanations in West Bengal Board Class 9 Life Science Book Solutions Chapter 1.3B Five Kingdoms of Life offer valuable context and analysis.

WBBSE Class 9 Science Chapter 1.3B Question Answer – Five Kingdoms of Life

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

Question 1.
Which type of cells are found among the members of kingdom Monera?
Answer:
Members of kingdom Monera have prokaryotic cells.

Question 2.
The cell wall of the members of kingdom Monera is made up of what?
Answer:
Cell wall of the members of kingdom Monera is made up of polysaccharides and amino acids.

Question 3.
Mention the nature of cells, found among the members of kingdom Protista.
Answer:
Members of kingdom Protista have eukaryotic cells.

Question 4.
Which cell wall component is found among the members of kingdom Fungi?
Answer:
Chitin is the cell wall component found amongst the members of kingdom Fungi.

Question 5.
Which major cell wall component is found among the members of kingdom Plantae?
Answer:
Cellulose is the major cell wall component, found amongst the members of kingdom Plantae.

Question 6.
Which type of nutrition is performed by the members of kingdom Plantae?
Answer:
Members of kingdom Plantae perform autotrophic mode of nutrition.

Question 7.
Which type of nutrition is performed by the members of kingdom Fungi?
Answer:
Saprophytic or parasitic nutrition is commonly performed by the members of kingdom Fungi.

Question 8.
Which type of nutrition is performed by the members of kingdom Animalia?
Answer:
Members of kingdom Animalia perform heterotrophic mode of nutrition.

Question 9.
Which members of living world perform the role of producers in any ecosystem?
Answer:
Members of kingdom Plantae perform the role of producers in any ecosystem.

Question 10.
Which members of living world perform the role of consumers in any ecosystem?
Answer:
Members of kingdom Animalia perform the role of consumers in any ecosystem.

Question 11.
Which members of living world perform the role of decomposers in any ecosystem?
Answer:
Members of kingdom Fungi perform the role of decomposers in any ecosystem.

Question 12.
Which members of kingdom Protista typically possess two flagella?
Answer:
Among the members of kingdom Protista, dinoflagellates typically possess two flagella.

Question 13.
Members of which kingdom perform the role of producers, consumers as well as decomposers in any ecosystem?
Answer:
Members of kingdom Protista perform the role of producers, consumers as well as decomposers in any ecosystem.

Question 14.
Members of which kingdom/kingdoms cause maximum number of human diseases?
Answer:
Members of kingdom Monera, Protista and Fungi cause maximum number of human diseases.

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

Question 1.
Name the five kingdoms of the living world, as proposed by Whittaker.
Answer:
The five kingdoms of the living world, as proposed by Whittaker are – Monera, Protista, Fungi, Plantae and Animalia.

Question 2.
What is meant by Monera?
Answer:
The word Monera has been derived from a Greek word ‘monos’, which means ‘single’. Monera is a kingdom of the living world, which is comprised of unicellular, microscopic and very primitive type of prokaryotic organisms. Example-Bacteria, blue-green algae etc. belong to this group.

Question 3.
What is meant by Protista?
Answer:
The word Protista has been derived from a Greek word ‘protistos’, which means ‘first of all.’ Protista is a kingdom of the living world, which is comprised of unicellular, eukaryotic, microscopic organisms. Example-Amoeba proteus, Euglena viridis etc.

Question 4.
What is meant by Fungi?
Answer:
The word Fungi has been derived from a Latin word ‘fungour’, which means ‘growing fast’. Fungi is a kingdom of the living world, which comprises eukaryotic, non-chlorophyllous, spore-bearing organisms, having cells with chitin-rich cell wall and performing both sexual and asexual reproduction. Example – Mucor mucedo, Aspergillus niger.

Question 5.
What is meant by eukaryotic cells?
Answer:
The cells, which possess well-organised nucleus and membrane-bound cell organelles, are known as eukaryotic cells. Example-The cells of all higher plant and animal cells.

Question 6.
What is meant by prokaryotic cells?
Answer:
The cells, which do not possess true nucleus and membrane-bound cell organelles, are called prokaryotic cells. Example-Bacteria, Mycoplasma, blue-green algae etc.

Question 7.
Mention two disadvantages of five kingdom classification.
Answer:
Two disadvantages of five kingdom classification are as follows-

• Different members Algae have been placed under three different kingdoms-blue-green algae under Monera, Euglena under Protista and brown algae under Plantae, which is ambiguous.
• Virus has not been included under any of the five kingdoms.

Question 8.
Which type of organisms are placed under kingdom Plantae?
Answer:
According to five kingdom classification of the living world, all chlorophyllous, photosynthetic, eukaryotic, multicellular organisms with cellulose containing cell wall, are included under kingdom Plantae.

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

Question 1.
Explain the basis of five kingdom classification.
Answer:
Basis of five kingdom classification
The characteristic features, based on which Whittaker proposed his five kingdom classification, are discussed below.
1. Complexity of cellular structure: On the basis of this feature, the living world is divided into two main divisions-

• Prokaryotes: Primitive forms without true nucleus.
• Eukaryotes: More complex forms along with true nucleus and membrane-bound cell organelles.

2. Complexity of body structure: Based on the number of cells present in a living body, organisms are classified into two groups-

• Unicellular: Body is made up of single cell.
• Multicellular: Body is made up of many cells. In case of multicellular forms, the nature of tissue and tissue systems are also taken into consideration.

3. Mode of nutrition: Living forms are classified into two main types, on the basis of their modes of nutrition. These are-

• Autotrophs: They are photosynthetic forms capable of preparing their own food.
• Heterotrophs: These are organisms which depend directly or indirectly on autotrophs for food.

4. Role in ecosystem: Based on their roles in ecosystem, living forms are classified into three types-

• Producers: They synthesise their own food within their body. Mainly photosynthetic green plants belong to this group.
• Consumers: They depend directly or indirectly on producers for food. These include all animals.
• Decomposers: They take part in biodegradation of organic matters. Various bacteria and fungi belong to this group.

5. Phylogenetic relation: Besides morphological, anatomical, biochemical and genetic features, the evolutionary trend of different groups are equally emphasized in this type of classification.

Question 2.
Compare the features of the five different kingdoms.
Answer:
Comparative features of the five kingdoms

Question 3.
Mention three identifying features of kingdom Monera. Give two examples of Monera.
Answer:
Identifying features of kingdom Monera
Three identifying features of kingdom Monera are as follows-
1. Ceil and cellular organisation : Members of this kingdom are unicellular, microscopic organisms. Their cells do not contain any membrane-bound organelle and membrane-bound true. nucleus is absent (i.e. prokaryotic). Genetic material is represented by a naked circular DNA. Ribosomes and chromatophores are present. Cell wall is composed of polysaccharides and amino acids.

2. Mode of nutrition: Nutritionally these are heterotrophic (parasitic, saprophytic, symbiotic) or autotrophic. Autotrophs are either photosynthetic or chemosynthetic. Among heterotrophs, saprophytes obtain nutrients from dead and decaying organic matters. Symbionts obtain nutrition by the help of other organisms.

3. Role in ecosystem: Photosynthetic and chemosynthetic forms play the role of producers. Heterotrophs act as consumers and saprophytes act as decomposers.

Two examples of Monera:
Two examples of Monera are Mycobacterium tuberculosis and Escherichia coli.

Question 4.
Mention three identifying features of kingdom Protista. Give two examples of Protista.
Answer:
Identifying features of kingdom Protista:
Three identifying features of kingdom Protista are as follows-

1. Cell and cellular organisation: These are unicellular, microscopic organisms. Cells contain membrane-bound cell organelles and true nucleus (i.e. eukaryotic). Nucleus contains chromosomes, which contain genetic material.

2. Mode of nutrition: These are heterotrophic (parasitic, symbiotic) or autotrophic in nature. Parasites obtain nutrients from the body of the host. Symbionts obtain nutrition by the help of other organisms.

3. Role in ecosystem: Photosynthetic forms (autotrophs) play the role of producers. Heterotrophs act as consumers.

Two examples of Protista
Two examples of Protista are Amoeba proteus and Euglena viridis.

Question 5.
Mention three Identifying features of kingdom Fungi. Give two examples of Fungi.
Answer:
Identifying features of kingdom Fungi
Three identifying features of kingdom Fungi are as follows-

1. Cell and celiular organisation: These are unicellular or multicellular eukaryotic organisms. Cell wall typically contains chitin. Glycogen is the distinctive stored food. Multicellular forms often develop hyphae or mycelium.

2. Mode of nutrition: These are mostly saprophytic. They collect nutrition from dead and decaying organic matters. Some are parasitic, which draw nutrition from living plants and animals. Few symbiotic forms obtain nutrition with the help of their photosynthetic partners.

3. Role in ecosystem: All saprophytic forms act as decomposers. Parasitic forms play the role of consumers.

Two examples of Fungi
Two examples of Fungi are Agaricus bisporus and Penicillium notatum.

Question 6.
Mention three identifying features of kingdom Plantae. Give two examples of Plantae.
Answer:
Identifying features of kingdom Plantae
Three identifying features of kingdom Plantae are as follows-

1. Cell and cellular organisation: These are multicellular, organisms. The cells contain membrane-bound organelles and nucleus is well-organised (i.e. eukaryotic). Cell wall is typically rich in cellulose and other polysaccharides. Plastids and large vacuole present in cells. Tissue and tissue systems develop in the body.

2. Mode of nutrition: All members are autotrophs, which perform nutrition by the process of photosynthesis.

3. Role in ecosystem: All members act as producers of the ecosystem.

Two examples of Plantae
Two examples of Plantae are sunflower (Helianthus annus) and Riccia glauca.

Question 7.
Mention three identifying features of kingdom Animalia. Give two examples of Animalia.
Answer:
Identifying features of kingdom Animalia
Three identifying features of kingdom Animalia are as follows-

1. Cell and cellular organisation: These are multicellular, eukaryotic organisms. Cells have centrioles. Cell wall and plastids are absent. Body with definite shape and size. Body has well organised tissues, tissue systems, organs and organ systems.

2. Mode of nutrition: All members are heterotrophs, which perform holozoic mode of nutrition.

3. Role in ecosystem: All members act as consumers of the ecosystem.

Two examples of Animalia
Two examples of Animalia are starfish (Asterias rubens) and pigeon (Columba livia).

Question 8.
Mention the advantages of five kingdom classification. According to five kingdom classification of the living world, which type of organisms are placed under kingdom Animalia?
Answer:
Advantages of five kingdom classification
The advantages of five kingdom classification are as follows-

• All unicellular prokaryotes are separated from eukaryotic unicellular protists and placed under kingdom Monera. So this classification is justified.
• Isolation of non-photosynthetic fungi from photosynthetic green plants is also justified because the mode of nutrition of fungi is different from that of green plants.
• Separating Protozoa from Animalia, makes the classification system more accurate.
• This classification rightly emphasises on the phylogeny of the living world.

Organisms under kingdom Animalia:
According to five kingdom classification of the living world, all heterotrophic, multicellular organisms, having cells without cell wall and holozoic mode of nutrition, are included under kingdom Animalia. It comprises all the consumers of different ecosystem.

Detailed explanations in West Bengal Board Class 9 Life Science Book Solutions Chapter 1.3A Classification of Diversity of Life: Taxonomy offer valuable context and analysis.

WBBSE Class 9 Science Chapter 1.3A Question Answer – Classification of Diversity of Life: Taxonomy

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

Question 1.
Who introduced the concept of species?
Answer:
The concept of species was introduced by John Ray.

Question 2.
Name the scientist who gave the modern definition of species.
Answer:
Scientist Ernst Mayr (1966) gave the modern definition of species.

Question 3.
Name the systematic framework of classification with fixed number of rank.
Answer:
The systematic framework of classification with fixed number of ranks, is called hierarchy.

Question 4.
What is the scientific name of India’s national fruit?
Answer:
The scientific name of India’s national fruit (mango) is Mangifera indica.

Question 5.
What is the full form of ICZN?
Answer:
Full form of ICZN is International Code of Zoological Nomenclature.

Question 6.
Before which year, the published scientific names of animals were considered invalid?
Answer:
Before the year 1758 , the published scientific names of animals were considered invalid.

Question 7.
Name an aquatic animal having same common name and generic name.
Answer:
Octopus is an aquatic animal, having same common and generic name.

Question 8.
Give an example of a fish having same generic and specific name.
Answer:
Scientific name of catla fish (Catla catla) has same generic and specific name.

Question 9.
Name the branch of biology that deals with identification, classification and nomenclature of organisms.
Answer:
The branch of biology that deals with identification, classification and nomenclature of organisms, is known as taxonomy.

Question 10.
In which edition of ‘Systema Naturae’ was the binomial nomenclature of animals accepted by ICZN?
Answer:
In the 10th edition of ‘Systema Naturae’, the binomial nomenclature of animals was accepted by ICZN.

Question 11.
Which year’s edition of ‘Species Plantarum’ was accepted by ICBN for binomial nomenclature of plants?
Answer:
The edition of ‘Species Plantarum’ published in the year 1753, was accepted by ICBN for binomial nomenclature of plants.

Question 12.
Define characterisation.
Answer:
Characterisation is an important feature of taxonomy which involves the process of listing the identifying features of collected specimen.

Question 13.
Name a terrestrial animal, having same common and scientific name.
Answer:
Gorilla is a terrestrial animal, which has same common name and scientific name (Gorilla gorilla).

Question 14
Which type of organisms are mostly known by their scientific names?
Answer:
Most of the protozoa are known by their scientific names, such as Amoeba, Paramoecium etc.

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

Question 1.
How did the word ‘taxonomy’ originate?
Answer:
The word ‘taxonomy’ originated from two Greek words-‘taxis’ meaning ‘rank’ and ‘nomos’, meaning ‘law’ or ‘custom’. Therefore, the word ‘taxonomy’ literally means the ‘custom of ranking.’

Question 2.
What are the three basic features of Linnaean taxonomy?
Answer:
Three basic features of Linnaean taxonomy are-

• Characterisation of living organisms based on certain observable features
• Naming the organisms according to binomial nomenclature and
• Placing the individuals into seven major levels of hierarchical ranks.

Question 3.
Mention the elements of discussion under taxonomy.
Answer:
The main elements of discussion under taxonomy are-

• identification
• nomenclature
• classification and
• documentation.

Question 4.
What is meant by identification?
Answer:
Identification is a taxonomic process of separating out any organism from a cluster of other forms, on the basis of its distinctive features.

Question 5.
What does spot identification mean?
Answer:
Spot identification is the process of separating out any plant or animal instantly from a cluster of other forms, on the basis of some external features.

Question 6.
What is meant by categorisation or grouping?
Answer:
The taxonomic process by which any organism is placed under a taxon or rank, based on its similarities with the other members of that group, is called grouping or categorisation.

Question 7.
What is meant by nomenclature?
Answer:
Nomenclature is a taxonomic process of providing a scientific name to a properly identified plant or animal, according to the internationally accepted rules in order to distinguish it from others.

Question 8.
What is classification?
Answer:
Classification is a taxonomic process of placing or grouping organisms into proper taxonomic categories on the basis of similarities in characters.

Question 9.
What is meant by documentation?
Answer:
Documentation is the scientific method of preservation of the type specimens, their description and all relevant data in museum or in laboratories, after the completion of taxonomic processes like identification, nomenclature and classification of a specimen.

Question 10.
What are taxonomic categories?
Answer:
Taxonomic categories are the units in which plants or animals are grouped during classification. Species, genus, family, order, class, phylum etc. are the examples of different taxonomic categories.

Question 11.
What is taxon?
Answer:
Taxon is the basic unit of hierarchy, which is a rank, given to a group of organisms with similar features, during classification.

Question 12
What is systematics?
Answer:
According to Simpson (1961), systematics is the scientific study of the kinds and diversities of organisms and relationship among them. The terms, systematics and taxonomy, often complement each other.

Question 13.
Mention the main objective of systematics.
Answer:
The main objective of systematics is to assort different organisms on the basis of their similarities and dissimilarities, so as to determine the inter-relationship amongst them and to point out their origin and trend of evolution.

Question 14.
Mention two problems of using common name of organisms with example.
Answer:
Two problems of using common names are:

• Common names vary with regional languages, due to which an organism cannot be recognised universally. For example, crow is called ‘kak’ in bengali, ‘kawa’ in hindi, ‘corneille’ in french, ‘karasu’ in japanese etc.
• Common name may create identity crisis. For example, silver fish is an insect, but the name apparently indicates a fish.

Question 15.
What is Linnaean hierarchy?
Answer:
The five-category system of hierarchical classification system proposed by Linnaeus in the 10th edition of his famous book, ‘Systema Naturae,’ is known as Linnaean hierarchy. He classified the living organisms into five categories, which was later modified into seven categories.

Question 16.
What is binomial nomenclature?
Answer:
Binomial nomenclature is the method of providing a scientific name to an organism. The name should contain two distinct epithets, the first one being genus and the second one is species. For example, Panthera tigris is the binomial nomenclature of tiger.

Question 17.
What is trinomial nomenclature?
Answer:
Trinomial nomenclature is the method of providing a scientific name to an organism where the name should contain three distinct epithets, genus, species and sub-species. For example, Homo sapiens sapiens is the trinomial nomenclature of human.

Question 18.
Mention the seven categories of modified Linnaean hierarchy.
Answer:
Seven categories of modified Linnaean hierarchy, from highest to lowest rank are
Kingdom → Phylum → Class → Order → Family → Genus → Species.

Question 19.
What is meant by structure of hierarchy? Represent the structure of Linnaean hierarchy.
Answer:

• Structure of hierarchy: The arrangement of all categories of hierarchy from the base to the top collectively forms the structure of hierarchy.
• Structure of Linnaean hierarchy: The structure of Linnaean hierarchy can be respresented as follows-

Question 20.
Mention the importance of classification.
Answer:
The importance of classification are as follows-

• By means of classification, an organism can be sorted out easily and quickly from a cluster of organisms.
• Classification helps to determine the inter-relationship amongst different groups of organisms.

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

Question 1.
Write down the brief history of the development of taxonomy in the pre-Linnaean period.
Answer:
Pre-Linnaean development of taxonomic science
Taxonomy is one of the oldest branches of biology, which has developed gradually since ancient time. The developmental phases of taxonomy, according to the ages, have been discussed below.

(1) Ancient age: The concept of taxonomy has developed in India about 2500 years back. The glimpse of classification was noticed in Rig veda, Manusamhita and Agnipuran. Manu, an ancient sage, classified plants into oshadhi, banaspati, briksha, gulma, trina and balli. In ‘Briksha ayurveda’, Rishi Parashar (1500 BC) classified plants on the basis of morphological features.

Susruta, the famous ancient Indian medic, classified medicinal plants into 37 genera. Greek philosopher, Aristotle (384-322 BC) classified animal kingdom in two divisionsAnaima (having colourless blood) and Enaima (having red blood). Theophrastus (371-287 BC), the disciple of Aristotle, described 480 species of plants and classified those into trees, shrubs and herbs, in his famous book, ‘The Historia Plantarum’

(2) Roman age: Famous Roman naturalist Pliny the Elder (23-79 AD), classified plants in his book, ‘Naturalis Historia’ on the basis of their medicinal qualities. Roman physician Discordies, described about 600 medicinal plants in his famous book ‘The Materia Medica.’

(3) Middle age: Italian botanist Caesalpino (1583), in his famous book ‘The Plantis’, classified 1500 plants into trees, shrubs and herbs. In his classification, he put emphasis on the character of fruits and seeds. For this great work, Caesalpino is regarded as the pioneer of plant taxonomy.

Gaspard Bauhin (1596) classified 6000 species of plants in his famous book ‘Pinax’. He was the first person who tried to show the difference between genus and species. Famous scientist John Ray (1627-1705), classified plants based on the basis of the number of cotyledon of seeds in his book ‘Methodum Plantarum’.

Question 2.
Write down the brief history of the development of taxonomy in pre-Linnaean period.
Answer:
Unnaeus’s role in developing modern taxonomy:

Modern taxonomy was set into light after the work of great Swedish scientist Carolus Linnaeus. He was the pioneer of scientific classification of plants and animals. In 1751, he first suggested the concept of binomial nomenclature in his famous book Philosophia Botanica

He studied numerous plants and animals, which he described in the latest edition of his two famous books, ‘Species Plantarum’ (1753) and ‘Systema Naturae’ (1758), respectively.

Taxonomists of post-Linnaean period:
Augustin de Candolle (1799), George Bentham (1862-1883), Joseph Dalton Hooker (1855), Adolph Engler, Karl Prantl (1887-1915), John Hutchinson (1926), Ernst Mayr (1963) are some of t

he renowned scientists who have enriched the taxonomic science to a great extent in the post-Linnaean period.

In last twenty years, there was immense development noticed in the field of systematic classification of plant kingdom based on phylogenetic analysis. Takhtajan (1997), Cronquist (1981) etc. played promising role in this aspect.

Question 3
What is meant by taxonomic hierarchy? How did Linnaean hierarchy modify in course of time?
Answer:
Taxonomic heirarchy
Taxonomic hierarchy is the sequential arrangement of various categories or units of classification comprising of different taxa, from larger to smaller ranks. This includes seven categories.

Modification of Linnaean hierarchy
In course of time, newer variants of organisms have been discovered. Modern taxonomists faced problems in positioning those variants in the prevailing seven-step format. Consequently, Simpson (1961) suggested a
21-step hierarchy for animal classification.

In this format, a new step ‘tribe’ was being inserted in between genus and sub-family. Besides this, some intermediate steps were also inserted in between the main steps prefixed with ‘supra,’ ‘sub’ and ‘infra’. Later, ICBN proposed a 24-step hierarchy structure.

Here, few more new steps were introduced, namely ‘section’ and ‘series’ between genus and species and ‘variety, ‘form’ and ‘clone’ after species. However, the intermediate steps, prefixed with ‘supra’ and ‘infra’ are discarded. Thus, the old Linnaean hierarchy is modernised in course of time.

Question 4.
Describe every category of taxonomic hierarchy with example.
Answer:
Categories of taxonomic hierarchy
Taxonomic hierarchy includes seven categories or ranks, which are described below.
1. Kingdom: It is the topmost category of taxonomic hierarchy. All different phyla or divisions constitute a kingdom. American scientist, R H Whittaker (1969) classified the whole living world into five different kingdoms-Monera, Protista, Fungi, Plantae and Animalia. Example-Human belongs to kingdom ‘Animalia’ and mango tree belongs to kingdom ‘Plantae.’

2 Phylum/Division: Related classes of animals constitute a phylum. In case of plants, this category is known as division. Example-In case of human, phylum is ‘Chordata’ and for mango tree, division is ‘Angiospermae.’

3 Class: A class consists of several related orders.
Example-Human belongs to class ‘Mammalia’ and mango tree belongs to class ‘Dicotyledoneae.’

4. Order: Several related families add up to create an order. Example-Human belongs to the order ‘Primates’ and mango tree belongs to the order ‘Sapindales’.

5. Family: All related genus together comprise a family. Example-Family of human is ‘Hominidae’ and for mango tree, it is ‘Anacardiaceae’.

6 Genus: Several related species constitute a genus. Example-Genus of human and mango tree are Homo and Mangifera respectively.

7 Species: It is the lowest category of taxonomic hierarchy. The taxon under this category include the group of naturally interbreeding organisms, which remain reproductively isolated from other related groups.
Example-Species of human and mango tree are sapiens and indica respectively.

Question 5.
What are the advantages of hierarchical classification? Mention the systematic position of mango tree according to Linnaean hierarchy.
Answer:
Advantages of hierarchical classification
The advantages of hierarchical classification has been discussed below.
1. Inter-relation amongst groups: Hierarchical system of classification provides ready information necessary to determine inter-relationships amongst two groups of plants or two groups of animals.

2. Flawless grouping: Before this system of classification, characteristic features of the sample specimens were studied vividly. Emergence of this system of classification helps us to study the characteristics of the sample specimens more specifically. Therefore, the grouping becomes flawless.

3. Easy identification of taxon: From a hierarchical classification, any taxon can be easily identified.

4. Other advantages: In this system of classification, repetition of characteristic features does not occur amongst the taxa of higher and lower categories. Only additional similarities are added to the lower categories.

Systematic position of mango tree
The systematic position of mango tree has been represented below.

Question 6.
Mention the rules of binomial nomenclature.
Answer:
Rules of binomial nomendature

The basic principles of binomial nomenclature was initially proposed by Linnaeus. Later in the 19th and 20th century, several international bodies of taxonomy, namely ICBN, ICZN, ICBacN, ICVN and ICNCPP reviewed the prevailing rules and published the final edited version of the rules of binomial nomenclature. The most important rules are as follows—

1. Every organism must have a definite scientific name in Latin or Greek, comprising of two epithets – a generic name and a specific name.

2. Each of the epithets must not be composed of less than three or more than twelve roman alphabets. The generic name is a noun, which should be written first, starting with a capital letter.

3. A generic name cannot be repeated in any other organism of the same or different kingdom.

4. Specific name should be written after generic name. It should be written in small letters.

5. A specific name may be repeated under different genus.

6. The name of the discoverer may be mentioned in full or in abbreviation, after the specific name.

7. A scientific name should be printed in italics. If handwritten, each epithet should be separately underlined. For example, scientific name of mango tree should be written as Mangifera indica L. (Here L. stands for Linnaeus, the discoverer).

8. Any plant name, used before publication of ‘Species Plantarum’ (1753) and animal name, used before publication of 10th edition of ‘Systema Naturae’ (1758) must be discarded.

9. If a single organism is assigned two different names by two separate discoverers in different times, the former will be accepted and the latter will be discarded. This is known as Law of priority.

10. Detailed description with photograph of the sample used for nomenclature, must be published in any internationally accepted science journal. The type specimen, used for the nomenclature, must be preserved in any museum competent for such job.

Question 7.
Mention the systematic position of human according to taxonomic hierarchy and the important characteristic features of different taxa.
Answer:
Systematic position of human and characteristic features of different taxa

MSBM	Taxon	Characteristic features
1. Kingdom	Animalia	Multicellular, cells without plastids and cell wall, heterotrophic, capable of locomotion
2. Phylum	Chordata	Notochord present at any stage of the life cycle, dorsal tubular nerve cord present, pharyngeal gill slits and post anal tail present
3. Class	Mammalia	Body covered with hair, sweat glands and sebaceous glands present in skin, mammary glands and external pinna present
4. Order	Primata or Primates	Palm and foot can grip any object, all digits have nails, vision is strong but sense of smell (olfactory sense) limited
5. Family	Hominidae	Body erect, capable of bipedal movement, hands shorter than legs
6. Genus	Homo	Brain is advanced and structurally complex, structure of palm is well developed (to use and prepare tools), capable of talking
7. Species	sapiens	High forehead, distinct lower jaw-line, culturally advanced

 

Detailed explanations in West Bengal Board Class 9 Life Science Book Solutions Chapter 1.2 Biology and its Branches offer valuable context and analysis.

WBBSE Class 9 Science Chapter 1.2 Question Answer – Biology and its Branches

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

Question 1.
What is anatomy?
Answer:
Anatomy is the study of the structure and location of internal organs and organ systems of animals and plants.

Question 2.
What is genetics?
Answer:
Genetics is the study of genes and hereditary features of organisms.

Question 3.
What is embryology?
Answer:
Embryology is the study of structure and development of embryos of living organisms.

Question 4.
What is evolutionary biology?
Answer:
Evolutionary biology is the study of origin of life and trends of changes in different forms of life with time.

Question 5.
What is biogeography?
Answer:
Biogeography is the study of distribution of plants and animals in different geographical regions.

Question 6.
What is cybernetics?
Answer:
Cybernetics is the science that deals with the technique of communications and control systems in both machines and living organisms.

Question 7.
What do you mean by hybridization?
Answer:
Hybridization is the process of crossing two genetically different individuals to produce an offspring with a different, often preferred, set of characters.

Question 8.
Mention any three branches of applied biology.
Answer:
Three branches of applied biology are — sericulture, apiculture and animal husbandry.

Question 9.
What is agriculture?
Answer:
Agriculture is the scientific practice of cultivation of commercially important crops.

Question 10.
What is horticulture?
Answer:
Horticulture is the scientific practice of production of flowers and fruits.

Question 11.
What is apiculture?
Answer:
Apiculture is the scientific practice of rearing honeybees in artificial hives and extracting honey from it.

Question 12.
What is sericulture?
Answer:
Sericulture is the scientific practice of rearing silkworms and extracting silk fibres from cocoons for economic purpose.

Question 13.
What is animal husbandry?
Answer:
Animal husbandry is the practice of breeding and rearing domestic animals like cattles, pigs, poultry birds etc. for production of milk, meat and eggs.

Question 14.
What is pharmacy?
Answer:
Pharmacy is the study of principles and practices of developing drug for therapeutic use in man, animals and plants.

Question 15.
What is silviculture?
Answer:
Silviculture is the study of principles and practices of cultivation of trees for wood and use of timber and its by-products.

Question 16.
What is entomology?
Answer:
Entomology is the study of different insects which are useful and harmful to man, animals and plants.

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

Question 1.
What is biology?
Answer:
The branch of science that deals with the study, investigations, experiments, observations and discussions on the origin, development, structural features and physiological activities of different living organisms, is known as biology

Question 2.
What do you mean by applied branches of biology?
Answer:
Applied branches of biology are those branches of biological science, in which, knowledge obtained from biology is applied for the welfare of human, animals and plants.

Question 3
What is zoology?
Answer:
The branch of biological science that deals with the study of morphology, anatomy, physiology, taxonomy, geographical distribution and conservation of animals, is known as zoology.

Question 4.
What is botany?
Answer:
The branch of biological science that deals with the study of morphology, anatomy, physiology, taxonomy, geographical distribution and medinical uses and conservation of plants, is known as botany.

Question 5.
What is physiology?
Answer:
The branch of biology that deals with the study of different activities and reactions related to various metabolic functions of living organisms, is called physiology.

Question 6.
What is taxonomy?
Answer:
Taxonomy is the oldest branch of biology, that deals with the identification, nomenclature and classification of living organisms on the basis of certain principles and processes.

Question 7.
What is microbiology?
Answer:
Microbiology is a branch of biological science, that deals with the study of microorganisms like virus, bacteria and all other microscopic organisms which are useful and harmful to human, animals and plants.

Question 8.
What is biochemistry?
Answer:
Biochemistry is a branch of science, developed by the combination of biology and chemistry. in order to study the nature of various chemicals, their classification and reaction processes occurring in the living organisms.

Question 9.
What is biophysics?
Answer:
Biophysics is an interdisciplinary branch of science, that is developed by (he combination of biology and physics. Ir deals with the study and explaination of the critical structure of various organs and the physical activities related to movement and locomotion, food capturing etc. of living bodies under the light of physics. Various instruments have been invented with the help of biophysics, such as endoscope, ultrasonograph, microscope etc.

Question 10.
What is molecular biology?
Answer:
The branch of biology that deals with the study of molecular structures of different intracellular biomolecules, their functions and applications, is known as molecular biology.

Question 11.
What is statistics?
Answer:
The branch of science, that deals with the collection, analysis and interpretation of data and finally presentation and organisation of the collected data, is known as statistics.

Question 12.
What is immunology?
Answer:
Immunology is a branch of science, that deals with the study of structure and function of body’s immune system and the nature of reactions occuring within the body between different antigens and antibodies.

Question 13.
What is astrobiology or exobiology?
Answer:
Astrobiology or exobiology is a combination of biology and space science, which is concerned with the study of the effect of hostile environment of outer space on various life activities of organisms on earth and different biochemical reactions.

Question 14.
What are the objectives of studying exobiology?
Answer:
The most important objective of studying exobiology is to find those organisms, that can withstand extreme conditions in space. Study of these organisms gives us an idea of those life forms, which came into being in extremely hostile environment of primitive earth. Study of this subject also gives us an idea of the reactions, which took place during abiogenesis of life on earth.

Question 15
Mention the different branches of cinical biology.
Answer:
The different branches of clinical biology are-immunology, serology, haematology, oncology, radiation biology, IVF (In vitro Fertilisation) technology, veterinary science etc.

Question 16
What is serology?
Answer:
Serology is the scientific study or diagnostic examination of blood and serum, especially with respect to the response of the immune system to pathogens or introduced substances.

Question 17
What is meant by pearl culture? What is lac culture?
Answer:

• Pearl culture: Pearl culture is a branch of applied biology that deals with the methods and techniques of rearing pearl oysters and extraction of pearl from them.
• Lac culture: Lac culture is a branch of applied biology that deals with the methods of rearing lac insects and extraction of shellac (a resin secreted by the female lac bug) from them.

Question 18.
What is meant by bioenergetics? What is thanatology?
Answer:

• Bioenergetics: The branch of biology that deals with the transformation of energy required for the synthesis and breaking up of biomolecules, is known as bioenergetics.
• Thanatology: Thanatology is the branch of science, that is concerned with the study of changes in a body after death and finding the cause of death.

Question 19.
What is bionics?
Answer:
Bionics is a new branch of science developed by the combination of biology and electronics to study the mechanical systems that function like living organisms or part of living organisms.

Question 20.
What is gerontology?
Answer:
Gerontology is a branch of science, that deals with ageing process. It is also known as geriatric studies. It mainly deals with the physical activities and problems faced during old age, senescence process of living cells, developing anti-oxidant medications etc.

Question 21.
What is biotechnology?
Answer:
Biotechnology is a broad discipline of bioscience, which involves the exploitation of biological processes for industrial and other purposes, especially the genetic manipulation of microorganisms for the production of antibiotics, hormones, etc.

Question 22.
Write two objectives of studying biology.
Answer:
Two objectives of studying biology are:

• To understand the relationship of living organisms with primary components of the environment and their interdependence.
• To gain knowledge about our local flora and fauna and developing healthy interaction with them.

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

Question 1.
Give a brief idea wa different brauches of classical biology.
Answer:
Branches of classical biology
Different branches of classical biology are discussed below.

• Morphology: This Is the branch of classical biology, that deals with the study of morphs I.e. size.
  shape and external features of living organisms.
• Cytology: This branch of biology deals with the study of structure and function of cells.
• Histology: The study of structure, distribution and function of tissues of living organisms, is called histology.
• Anaty: [his branch of biology deals with the structures of different Internal organs of plants and animals.
• Pyslolog: This is the branch of classical biology, that involves the study of various metabolic reactions and the functional activities of life.
• Genetics: This branch of biology deals with the study of heredity and variations of inherited features.
• Evolutionary biolo: This is the study of origin of life and gradual complexities of organisms.
• Ethology: This branch of biology is concerned with the study of behaviour of organisms.
• Ecology: This branch of classical biology deals with the study of interrelation between organisms and the environment.
• Taxonomy: This is the oldest branch of classical biology that deals with the theoritical study of classification of living organisms including its basic principles and processes. It involves identification, nomenclature and classification of organisms.
• Immunology: This branch of science deals with the study of immune system of our body and the reactions of antigens and antibodies occuring in our body.
• Embryology: This branch of science deals with the structure and development of embryo of living organisms.
• Pathology: This branch of science deals with the study of different diseases, their causes and preventive measures.
• Paleontology: This branch of classical biology deals with the study of extinct organisms, through their fossils and, thus, knowing their geological history.

Question 2.
Give a brief idea on different branches of applied biology.
Answer:
Branches of applied biology
Different branches of applied biology are discussed below.
1. Agriculture: This branch of applied biology deals with the practice of cultivation of crops and vegetables.

2. Horticulture: This is a branch of applied biology, which deals with the scientific practice of cultivation of flowers and fruits.

3. Forestry: This branch of applied biology deals with the methods, which help to reduce deforestation, such as afforestation and conservation of forest.

4. Pharmacognosy: This branch of science deals with the rearing and conservation of medicinal herbs and study of crude drugs and herbal medicines.

5. Sericulture: This branch of science deals with the scientific practice of rearing silkworm and extracting silk fibres from cocoons, for economic interest.

6. Pisciculture: This branch of applied biology deals with the scientific practice of breeding, rearing and capturing fishes for economic purpose.

7. Apiculture: This branch of science deals with the scientific practice of rearing honeybees in artificial hives and extracting honey from them.

8. Pearl Culture: This is a branch of applied biology, that deals with the methods of rearing pearl oysters and extraction of pearl from them.

9. Lac culture: This branch of applied biology deals with the methods of rearing lac insects and extraction of shellac from them.

10. Poultry farming: This branch of applied biology deals with the breeding and rearing of poultry birds, for the production of eggs and meat.

11. Dairy farming: This branch of applied biology deals with the rearing of cattle for the production of milk.

12. Animal husbandly : This branch of applied biology deals with the practice of breeding of farm animals (cattle, pigs, horses etc.) in order to develop their genetic qualities for human profit.

13. Plant breedhg This branch of applied biology deals with various methods for production of improved variety of plants.

14. Molecular biology : The branch of science that deals with the study of different biomolecules and their activities within our body, is known as molecular biology.

15. Biochemistry : This branch of science deals with the study of chemical processes occurring inside living organisms.

16. Microbiology: It is the study of microorganisms that are useful or harmful to man, plants and animals.

Question 3.
Mention the relationship of biology with other branches of science.
Answer:
Relationship of biology with other branches of science:
In course of time, biological science has developed further by sharing its concepts with other fields of science. This gave rise to some new and modern branches of science subjects. Some of these are discussed below.

1. Biophysics: This branch of science has been developed by the combination of biology and physics. It deals with the study and explanation of the critical structures of various organs and physical activities related to movement, locomotion, food capturing etc. of living bodies, under the light of physics.

2. Biochemistry: This is a branch of science, developed by the combination of biology and chemistry. It deals with the study of nature of various chemicals, their classification and reaction processes occurring in the living organisms.

3. Biotechnology: This is a modern branch of science, developed for producing improved variety of plants or animals for human benefit, by means of genetic manipulation.

4. Biometry: This is a branch of science, developed by combination of biology, mathematics and statistics. This subject helps to analyse different events and facts of biology, under the light of statistics.

5. Bionics: This branch of science has developed by the combination of biology’ and electronics. This is the study of mechanical systems which function like living organisms or parts of living organisms.

6. Biogeography: This branch of science has developed by the combination of biology and geography. It deals with the study of the distribution of flora and fauna in different geographical regions.

7. Anthropology: This branch of science has been developed for the study of humankind, under the light of geography, sociology and palaeontology.

8. Palaeontology: This branch of science is developed by the combination of biology and geology. It deals with the study of the fossils of primitive life forms.

9. Bioinformatics: This branch of science has been developed by the combination of biology and computer science. It deals with the analysis of complex biological data, especially genetic codes.

10. Astrobiology or exobiology: This is a modern branch of science, developed by the combination of biology and space science to study the effect of environment of outer space on living organism of earth.

Question 4.
Explain the applications of biology in various fields.
Answer:
Applications of biology:
Some important applications of biology are discussed below.

1. Development in agriculture: The ever-growing population of our country led to the problem of food scarcity, thereby increasing the demand for food. Application of biology has solved this problem to a great extent. Biology is applied at its best in the field of agriculture, to increase the productivity and quality of crops. Various fields of application of biology in agriculture are —

• Production of high-yielding varieties of crops: By using the knowledge of genetics and applying the techniques of hybridization, high-yielding varieties of paddy, wheat, maize and several other crops have been successfully produced.
• Production of seedless fruits: Concept of genetics and horticulture are combined to produce seedless varieties of fruits and to improve the productivity and size of fruits.
• Pest control: Concept of biotechnology has been applied to develop certain pest resistant varieties of crops and vegetables. Several pests are now controlled biologically by using predators and parasites.
• Storing of crops and food: Inventions in the field of biology help us to protect and preserve crops and food for a longer period of time. ‘

2. Fish production: Knowledge of biology has been applied in induced breeding technique and composite fish culture, to increase fish production and to meet the growing demand.

3. Poultry and dairy: Knowledge of biology has been used for the advancement of poultry and dairy farming techniques. By this process, the production of eggs, meat and milk has been increased.

4. Preparation of medicines: Herbal medicines are used since ancient times. Study of biology has revealed several medicinally important plants and animal products, which are used for the benefit of human and animals. Knowledge of microbiology has helped to produce a number of antibiotics, such as penicillin, streptomycin, neomycin, tetracycline etc.

5. Application of biology in space: Chlorella is the most photosynthetically efficient green alga. It is cultured in space stations, to maintain a continuous supply of oxygen and removal of carbon dioxide. Many microbes and other organisms are studied in space laboratories to know the effect of extreme conditions of space on life forms.

6. Industrial production: Industries like sericulture, lac culture, pearl culture are different wings of biology. The concepts of biology are utilised to increase the production of cosmetics, medicines, textile, paper, plastic, rubber, leather, wood, tea, coffee, bakery and brewery industries.

7. Controlling environmental pollution: Biological notions help us to control environmental pollution. Afforestation, social forestry and conservation of forest are some of the positive steps, undertaken globally for pollution control.

8. Population control: Population explosion is the burning problem of present world. By applying different concepts of biology and medicine, scientists have invented different modern and effective birth contol techniques for controlling population.

Detailed explanations in West Bengal Board Class 9 Life Science Book Solutions Chapter 1.1 Basic Properties of Life offer valuable context and analysis.

WBBSE Class 9 Science Chapter 1.1 Question Answer – Basic Properties of Life

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

Question 1
Mention five common signs of life.
Answer:
Reproduction, growth, metabolism, response to stimuli and adaptability are the five common signs of life.

Question 2.
What does reproduction mean?
Answer:
Reproduction is the biological process by which new individuals or offsprings are produced from their parents.

Question 3.
Define excitability.
Answer:
Excitability is defined as a response of a living organism to any external and internal stimulus.

Question 4.
What is meant by response?
Answer:
The reaction shown by a living organism towards any impulse, is called response.

Question 5.
What does metabolism mean?
Answer:
A set of complex physiological and chemical processes necessary for sustaining life, involving formation and breakdown of various nutrients within the body is called metabolism.

Question 6.
What is growth?
Answer:
Growth is the irreversible increase in dry mass and size of a living body.

Question 7.
What is meant by biopoiesis?
Answer:
Biopoiesis is the concept of the origin of living organisms from non-living matters.

Question 8.
Who first suggested that living organisms originated from non-living matters?
Answer:
Philosopher Aristotle first suggested that living organisms originated from non-living matters.

Question 9.
From where did primary organic micromolecules originate from inorganic compounds?
Answer:
Primary organic micromolecules originated in the primitive atmosphere from simple inorganic compounds.

Question 10.
How was the atmosphere on earth before the origin of life?
Answer:
Before the origin of life, earth’s atmosphere was reducing in nature.

Question 11.
Why the atmosphere of primitive earth was reducing in nature?
Answer:
The atmosphere of primitive earth was reducing in nature because there was no free oxygen in the atmosphere.

Question 12.
Name the two scientists who suggested that organic micromolecules originated on earth by chemical reactions amongst simple inorganic compounds.
Answer:
Scientists Alexander Oparin and JBS Haldane, first suggested that organic micromolecules originated on earth by chemical reactions amongst simple inorganic compounds.

Question 13.
How did primary organic micromolecules reach the earth’s surface?
Answer:
Primary organic micromolecules reached the earth’s surface through rainwater.

Question 14.
Who coined the term ‘primordial soup’?
Answer:
Scientist A1 Oparin coined the term ‘primordial soup’ to denote the primitive oceanic water rich in organic matter.

Question 15.
Which term was used by Haldane to indicate the boiling hot oceanic water of the primitive earth rich in organic matter?
Answer:
Haldane denoted the organic matter-rich boiling hot oceanic water of the primitive earth as ‘hot dilute soup’.

Question 16.
What are proteinoids?
Answer:
Proteinoids are tiny clusters of protein molecules formed abiotically from amino acids by cross-linkage.

Question 17.
What are microspheres?
Answer:
Microspheres are spherical clusters of proteinoids, covered with thin film of phospholipids.

Question 18.
Name two primitive forms, which are considered as predecessors of living organisms on earth.
Answer:
Microspheres and coacervates are two primitive forms, which are considered as predecessors of living organisms on earth.

Question 19.
Which organic matters constitute a protobiont?
Answer:
A protobiont is constituted of organic matters like nucleic acids, lipids and various protein molecules.

Question 20.
What is meant by alpha (α) diversity?
Answer:
Alpha (α) diversity indicates the richness of species in a specific area or an ecosystem.

Question 21.
What is meant by beta (β) diversity?
Answer:
Beta (β) diversity is the measure of the comparative turnover of species in two different habitats of an ecosystem.

Question 22.
What is meant by gamma (γ) diversity?
Answer:
Gamma (γ) diversity is the overall biodiversity of a large geographical realm, consisting of many typical habitats and ecosystems.

Question 23.
What are the two main causes of biodiversity on earth?
Answer:
Genetic variation and natural selection are the two main causes of biodiversity on earth.

Question 24.
Which class of animals shows the highest level of diversity in India?
Answer:
In India, birds show the highest level of diversity, where about 12.6% of global bird species are found.

Question 25.
What is meant by biodiversity hotspot?
Answer:
Biodiversity hotspot is a geographical area that provides shelter to a very rich variety of endemic species that are facing the threat of extinction.

Question 26.
How many biodiversity hotspots are there in India?
Answer:
In India there are three biodiversity hotspots-the Western Ghats, the Himalayas and the Indo-Burma regions.

Question 27.
How many biodiversity hotspots are there in the World?
Answer:
According to Conservation International (2004), there are 34 hotspots in the world.

Question 28.
Which type of diversity is also known as turnover diversity?
Answer:
Beta diversity is also known as turnover diversity.

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

Question 1.
What is life?
Answer:
Life is the condition that establishes the existence of a living organism on the basis of various characteristics such as growth, reproduction, metabolic activities, response to stimuli, adaptability, ageing, death etc.

Question 2.
What are non-living objects?
Answer:
Those objects which do not show any of the signs of life, such as growth, reproduction, metabolic activities, response to stimuli, ageing and senescence etc., are called non-living objects.

Question 3.
What is meant by life cycle?
Answer:
The cyclic course of events undergone by an organism, starting from its birth followed by growth, maturity, reproduction, ageing and finally death, is known as its life cycle.

Question 4.
Define heredity.
Answer:
Heredity is the process of transfer of different characteristics from parents to their offsprings.

Question 5.
What is evolution?
Answer:
Evolution is the slow, steady and continuous emergence of advanced and complex forms of life from primitive and simpler forms. It also involves change in heritable characters of biological population from one generation to the next.

Question 6.
What is meant by mutation? What is mutability?
Answer:

• Mutation: Mutation is a sudden, permanent and inheritable transformation in living organisms, caused due to any change in chromosome or gene either naturally or by any external factor.
• Mutability: The capacity of a living organism to undergo mutation is called mutability.

Question 7.
What is meant by variation?
Answer:
The dissimilarities in external or internal features or behaviours found amongst the different members of a species in a population, is called variation.

Question 8.
Give an example of response to stimuli shown by plant.
Answer:
The leaves of ‘touch me not’ (Mimosa pudica) plant droop when touched. This is an example of response to stimuli shown by a plant.

Question 9.
What is meant by senescence?
Answer:
Senescence is the process of gradual and irreversible deterioration in the structural components of the body and decrease in the ability of a matured organism to deal with the stress of the environment.

Question 10.
what is meant by ageing? What is death?
Answer:

• Ageing: Ageing is the process of growing older with time, that is genetically determined and environmentally modulated.
• Death: Death is the ultimate disappearance of all signs of life from a living organism.

Question 11.
What does the ‘Ghemogeny of life’ mean?
Answer:
Chemogeny or chemosynthesis of life is the most modern concept, used to explain the biochemical origin of life on the earth. According to this concept, life originated naturally and spontaneously from simpler inorganic matters on earth, through various physical and chemical processes.

Question 12.
What is meant by ‘hoi dilute soup’?
Answer:
According to the theory of chemosynthesis, several organic molecules accumulated in the hot boiling water of the primitive ocean before the origin of life. Haldane denoted this hot broth of organic matter as ‘hot dilute soup!

Question 13.
What are coacervates?
Answer:
Coacervates are minute (1-100μ in diameter), spherical, bubble-shaped, colloidal matters, composed of a thin layer of organic molecules rich in lipids. Oparin (1924) first suggested this structure and named it coacervate.

Question 14.
Mention the living features of microspheres.
Answer:
The living features of microspheres are as follows —

• They are surrounded by a double-layered membrane
• They show osmotic activity.
• Certain protein molecules present in the microspheres, have enzymatic activity
• Microspheres may divide through a process similar to binary fission.

Question 15.
What are proiocells?
Answer:
In the primitive sea, nucleic acid molecules entered into protein coacervates to take the shape of primitive cells. These primitive structures are known as protocells, in which the first sign of life was noticed.

Question 16.
What are naked genes?
Answer:
According to the chemosynthetic theory, during the last phase of ceil formation, purines, pyrimidines and pentose sugars united to form nucleic acids. These nucleic acid molecules were capable of seif-replication. They were devoid of histone and other proteins and as they were not surrounded by nuclear membrane. They were called naked genes.

Question 17.
What is meant by biodiversity?
Answer:
Biodiversity refers to the variety of different types of living organisms on the basis of structure, shape and behaviour found on earth, that are inhabiting different habitats of various ecosystems.

Question 18.
What is meant by genetic diversity?
Answer:
The different types of variations and combinations in the genetic composition among the individuals of a species is considered as genetic diversity. Due to genetic diversity, different individuals of same species look and behave differently.

Question 19.
What is meant by species diversity?
Answer:
The diversity in number, richness and evenness in distribution of various species in a biotic community is regarded as species diversity. This is estimaed by determining the number of variety of a species and the number of species Inhabiting a specified area.

Question 20.
What is meant by ecological diversity?
Answer:
The variation of several ecosystems in a large geograpical area or throughout the planet. is known as ecological diversity. The diversity of organisms from a microhabitat to a huge hiome is included under ecological diversity.

Question 21.
What is meant by species?
Answer:
Species is a group of closeI related individuals, which are capable of naturally interbreeding to produce fertile offsprings. They remain reproductively isolated from other groups.

Question 22.
How do variation occur In a population?
Answer:
Almost every individual of any sexually reproducing population is slightly different from one another. There are three main reasons behind —

• Formatilin of different types of ganletes I due to crossing over,
• Random union of gametes and
• Change in the genetic material.

Question 23.
Give a brief note on the biodiversity of India.
Answer:
The biological diversity of India includes a huge variety of plant and animal species, their genetic variability and the organisation of species into different ecosystems. India is one of the seventeen megadiverse countries on earth. In global perspective, India houses about 7.6% of all mammals, 12.6% of all birds, 6.2% of all reptiles, 4.4% of all amphibians, 11.7% of all fishes and 6.0% of all flora.

Question 24.
What are the reasons for the loss of biodiversity?
Answer:
The main reasons for the loss of biodiversity are-

• Deforestation,
• Habitat fragmentation,
• Environmental pollution,
• Over exploitation of resources by Illegal hunting and poaching,
• Natural calamities,
• Alteration of natural environment due to green house effect, ozone layer depletion etc.,
• Genetic incompatibility,
• Introduction of exotic species etc.

Question 25.
What are the contributing factors of biodiversity?
Answer:
The contributing factors of biodiversity are-

• Variation
• Mutation
• Speciation
• Adaptation
• Geographical isolation
• Change in climatic condition
• Change in habitat etc.

Question 26.
Compare between coacervate and microsphere.
Answer:

features	Coacervate		Microsphere
1. Definition	These are minute spherical, bubble-shapped structures originating in the ‘hot dilute soup’		These are spherical clusters of proteinoids covered by a thin film of lipid bilayer
2. Function	Plays an important role as the precursor of protocell		Plays an Important role as the precursor of the early or primitive cell
3. Structural component	Structure is composed of protein, fat, carbohydrate and nucleic acid		Structure is composed mainly of proteins formed from proteinoids

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

Question 1.
Explain the basic properties of lite.
Answer:
Basic properties of life
From biological point of view, there are five basic properties of life. They are —

(1) Reproduction: Reproduction is a biological process by which living organisms give birth to offsprings in their lifetime, in order to protect their races from becoming extinct.

(2) Growth: Growth is the irreversible increase in dry mass and size of a living body. A living organism must exhibit growth and development in due course of time.

(3) Metabolism: Metabolism is a set of life sustaining chemical reactions involving formation and breakdown of various nutrients within the body. Different metabolic activities like nutrition, respiration, excretion etc. take place in a living organism.

(4) Response to stimuli: Response to external and internal stimulus is an important character of a living organism. For example, if a moving millipede is touched, it coils around.

(5) Adaptability: Adaptability is a property of life where any living organism tries to adjust itself, either structurally or behaviourally, according to the changing environment.

Question 2.
Mention the differences between living beings and non-living objects.
Answer:
Differences between living beings and non-living objects

Features	Living beings	Non-living objects
1. Reproduction	Living beings maintain their race by reproduction	Non-living objects do not reproduce
2. Response to stimuli	Living beings respond to external or internal stimuli	Sensitivity to stimulus is absent in non-living objects
3. Growth	Living beings grow gradually with time	Non-living objects never show any growth
4. Metabolism	Living beings perform various metabolic activities like photosynthesis, nutrition, respiration etc.	Non-living objects never perform any metabolic function
5. Life span	Ali living forms have a definite life span	Non-living objects do not have any specific duration of existence
6. Movement and locomotion	Living beings spontaneously exhibit movement and locomotion	Movement occurs as a result of external influence
7. Protoplasm	Cells of living organisms have active protoplasm	Protoplasm is absent

8. Adaptability	Living organisms can adapt themselves according to changing environment		Non-living objects do not show any adaptation
9. Life cycle	Living organisms have life cycle		Non living objects do not have life cycle
10. Senescence and death	Living organisms show signs of senescence and death		Non-living objects do not show signs of senescence and death

Question 3.
Briefly describe the origin of earth and gradual changes in the primitive atmosphere according to the theory of chemosynthesis of life.
Answer:
Origin of earth and gradual changes in the primitive atmosphere
According to the theory of chemosynthesis of life or the theory of abiogenesis about 5-6 billion years ago, the earth originated from a huge explosion known as the Big Bang in the cosmos. At that time, the earth was a mass of burning gas. It took several million years to cool down and condense.

The temperature of primitive earth was around 5000°C — 6000°C. At that high temperature, it was difficult for certain gases such as hydrogen, nitrogen and oxygen etc. to exist independently in the atmosphere. As a result, they were present in the form of metallic or non-metallic compounds.

Therefore, the primitive atmosphere was reducing in nature due to the absence of free oxygen. With gradual decrease in temperature, water vapour condensed to form huge clouds, which came down on the earth in the form of rain. Gradually, the earth started to cool down further and condensed to form solid matters. The rainwater accumulated in the lowlands to form the primitive ocean.

Question 4.
Briefly describe chemogeny of life.
Answer:
Chemogeny of life
The process of synthesis of various organic compounds essential for the origin of life on the earth, was denoted as chemogeny by scientists Oparin and Haldane. This involves 3 steps. The steps of chemogeny are discussed below.

1. Origin of simple organic compounds: With gradual decrease in atmospheric tempertaure, the chemical components like hydrogen, methane, ammonia, water vapour etc., started reacting with each other to form simple organic molecules such as amino acids, simple sugars, fatty acids etc. The energy required to carry out these reactions was provided by lighting, ultraviolet ray and different cosmic rays. Through downpour, these compounds precipitated on earth and mixed in the primitive ocean.

2. Formation of complex organic compounds: The simple organic molecules condensed in the primitive ocean to form complex organic compounds such as proteins, carbohydrates, lipids, purines, pyrimidines etc. The boiling hot water of the primitive ocean containing the complex organic compounds was denoted as hot dilute soup by Haldane. Oparin termed the same as primordial soup.

3. Formation of coacervates: In the hot dilute soup, the organic matters, especially lipids, clustered to form a self-organised colloidal matter. Oparin named this bubble-shaped structures as coacervates. American scientist Sidney Fox (1957), denoted a similar substance as microsphere, which, according to him, was formed by unification of several globoid duster of proteins, called proteinoids, surrounded by a double-layered lipid membrane.

Question 5.
Explain biogeny or organic evolution of life.
Answer:
Biogeny or organic evolution of life:
According to Oparin, as the temperature of the atmosphere gradually started to cool down and simple organic compounds reacted with each other to form complex organic compounds by chemosynthesis, the boiling hot water of primitive ocean acted as the site of formation of lipid clusters, called coacervates. These coacervates absorbed nucleic acids and proteins from the primordial soup and transformed into a structure, capable of performing few metabolic activities which were named as protobionts.

The protobionts were capable of synthesising some organic matters within it through various chemical reactions. Later, these protobionts transformed into self-replicating organic matters, which the scientists denoted as eubionts. These were the first living entity on earth. Later, cytoplasm formed within them and thus the earliest prokaryotic cells came into being.

Question 6.
Classify different levels of biodiversity.
Answer:
Levels of biodiversity : Biodiversity has been classified into three levels-

• Genetic diversity,
• Species diversity and
• Ecological diversity,

1. Genetic diversity: The various types of variations and combinations in the genetic composition among the individuals of a species is considered as genetic diversity, Due to genetic diversity, individuals of same species look and behave differently. Example -The diversity in the genes of different varieties of paddy, wheat, dogs, etc.

2. Species divesity : The diversity in number, richness and evenness in distribution of various species in a biotic community is regarded us species diversity. This is estimated by determining the number of variety of a species and the number of species inhabiting a specified area. Example –The diversity of species inhabiting the mangrove forest of Sundarban.

3. Ecological diversity: The variation of several ecosystems in a large geographical area is known as ecological diversity. The diversity of organisms from a microhabitat to a huge biome is included under ecological diversity. American ecologist Whittaker (1965), classified ecological diversity into three different sub-types. They are—

• α diversity: α diversity indicates the richness of species in a specific area or an ecosystem.
• β diversity: β diversity is the measure of comparative turnover of species in two different habitats of an ecosystem.
• γ diversity: γ diversity is the overall biodiversity of a large geographical realm, consisting of many typical habitats and ecosystems.

Question 7.
Describe the different types of variation along with their examples and significance.
Answer:
Types of variation
Variation is broadly classified into two types—

• Continuous variation and
• Discontinuous variation.

Continuous variation: Any characteristic of a species that changes gradually over a range of values is considered to exhibit continuous variation. It is represented by a line graph. Example — Variation in human height, skin colour and weight

Significance — Continuous ‘variation creates diversity amongst the members of same species. The characteristic features which undergo natural selection are ultimately transferred to the next generation.

Discontinuous variation: Any characteristic of a species having only a limited number of possible values is considered to exhibit discontinuous variation. It is represented by a bar graph. Example — Variation in human blood group and human eye colour.

Significance — Mutation is the prime reason behind discontinuous variation. Mutation leads to the development of new species at a comparatively faster rate. Discontinuous variation leads to species diversity.

Question 8.
What are the important features of biodiversity?
Answer:
Important features of biodiversity
The important features of biodiversity are as follows –

• Comparatively high level of biodiversity has been noticed in tropical and subtropical region than temperate region.
• Rate of biodiversity is very high in tropical rain forests in terrestrial ecosystem and coral reefs in aquatic ecosystem.
• Insects are the diverse of all living organisms (56.4% of total species).
• Reduction of genetic diversity of a species gradually leads to its extinction.
• Biodiversity is not evenly distributed in all parts of the world.

WBBSE Class 9 Life Science Question Answer West Bengal Board

WBBSE Class 9 Life Science Book Solutions West Bengal Board in English Medium

• Chapter 1 Life and its Diversity
  • Chapter 1.1 Basic Properties of Life
  • Chapter 1.2 Biology and its Branches
  • Chapter 1.3A Classification of Diversity of Life: Taxonomy
  • Chapter 1.3B Five Kingdoms of Life
  • Chapter 1.3C Classification of Kingdom Plantae
  • Chapter 1.3D Classification of Kingdom Animalia
• Chapter 2 Levels of Organisation of Life
  • Chapter 2.1 Biomolecules and their Behaviour
  • Chapter 2.2 Cell
  • Chapter 2.3A Tissue: Plant Tissue and its Distribution
  • Chapter 2.3B Tissue: Animal Tissue and its Distribution
  • Chapter 2.4 Major Organs of Human Body and Their Function
• Chapter 3 Physiological Processes of Life
  • Chapter 3.1A Plant Physiology: Photosynthesis
  • Chapter 3.1B Mineral Nutrition
  • Chapter 3.1C Transpiration
  • Chapter 3.1D Movement of Water, Minerals, Food and Gases
  • Chapter 3.2A Respiration: Organ-Level Respiration
  • Chapter 3.2B Cellular Level Respiration
  • Chapter 3.3 Nutrition
  • Chapter 3.4 Circulation
  • Chapter 3.5 Excretion
• Chapter 4 Biology and Human Welfare
  • Chapter 4.1 Immunity and Human Diseases
  • Chapter 4.2 Microbes in Human Welfare
• Chapter 5 Environment and its Resources
  • Chapter 5.1 Ecology and Ecological Organisations
  • Chapter 5.2 Natural Resources and its Sustainable Use

WBBSE Class 9 Life Science Book Solutions West Bengal Board in Hindi Medium

• Chapter 1 जीवन एवं उसकी विविधता
• Chapter 2 जीवन गठन के स्तर
• Chapter 3 जीवन की शारीरिक क्रियाएँ
• Chapter 4 जीव विज्ञान एवं मानव कल्याण
• Chapter 5 वातावरण तथा उसके संसाधन

WBBSE Class 9 Life Science Syllabus West Bengal Board 2024

Chapter 1 Life and its Diversity
Basic Properties of Life: How a living being is different from a non-living object?
Life shows some basic properties that are absent in non-living objects, e.g., the capacity to reproduce itself/new life, to uptake and use energy (metabolism), to respond to stimuli, etc. Explain in brief and in a simple way the basic properties of life with examples.

How does life come into being on Earth and when?
Chemical Origin of Life from Non-living Objects some 3.7 billion years ago; And then the evolution of the diversity of life forms from the earliest life form. A brief outline of the abiotic origin of life: pre-biotic conditions → precursor, biomolecules → coacervate/microsphere → protocells → earliest life forms.
Sources of Variations in Life: Heritable chance variations arise during the reproduction of living organisms and their adaptations to varying environments; Amount of diversity of the (biodiversity)-more than 30 million species and further variations within a species.

Biology is the Study of Patterns and Processes of Life and its Diversity: Why study Biology?
Biological studies at different levels and aspects. Different branches of Biology: what do they study (e.g. Biochemistry, Molecular biology, Immunology, Genetics, Histology, Anatomy, Physiology, Ecology, Behavioural Biology, Evolution, and other branches). Infusions of knowledge from other branches of science into Biology. Application of Physics, Chemistry, Mathematics, Statistics, Computers, and other branches; emergence of new branches of Biology. Applications of Modern Biology: Applications of Biology in agriculture, medicine, space science, and in other fields.

Classification of Diversity of Life: Taxonomy:
(a) Taxonomy and Taxonomic Hierarchy: Why taxonomy? What are the basic features of Linnaean taxonomy?
Development of modern taxonomy in Europe when naturalists started encountering a high diversity of new living organisms, especially from the tropics. A very brief history regarding the birth of modern taxonomy till Linnaeus. Hierarchical arrangement of classified groups. Explain the seven steps of taxonomic hierarchy schematically-(kingdom to species)-concerning one example from a plant (Mango) and one from an animal (Man). Binomial nomenclature: Explain briefly binomial nomenclature with an example.

(b) Five Kingdoms of Life: Five kingdoms of life: Name five kingdoms of life, mentioning three salient features of each kingdom-nature of cell and cellular organization, metabolic process, ecological role, and two common examples.

(c) Classification of Kingdom Plantae: How do different plants differ from each other?
Major groups (Algae, Bryophyta, Pteridophyta, Gymnosperm Angiosperm-Monocotyledon, and Dicotyledon). Comparing the distinguishing features of major groups with examples (tabular form).

(d) Classification of Kingdom Animalia: How different animals are similar and different from each other?
All major Phyla under Non-Chordata; Classification of Chordates upto class level. Three distinguishing features and two common examples of each group.

Chapter 2 Levels of Organization of Life
Biomolecules and their Behaviour: What are we made up of? Why these compounds are so important for our existence?
Elementary idea about the compounds of life-inorganic: water, acids, bases, salts, gases, etc. Organic: (i) Smaller molecules – simple sugars, amino acids, fatty acids, nucleotides (ii) Macromolecules-complex carbohydrates, protein, lipid, and nucleic acids. Different categories of biomolecules with examples (in a chart). Basic structural/compositional features of each type of biomolecule (detailed structure to be avoided). The major role of them in life processes (e.g. proteins act as structural materials, enzymes, etc. Role of ATP as the energy currency of a cell, etc.). Vitamins: Vitamin A, D, E, K, B-complex & C and their roles in the human body. Minerals: Mention the names of different minerals and their general role in the human body.

Cell: What are the organelles of a cell and how a cell is organized with such organelles?
Cell wall, cell membrane, cytoplasm, nucleus, mitochondria, plastid, endoplasmic reticulum, Golgi body, lysosome, vacuole, ribosome, centriole, microtubule. Elementary idea about the structures and functions of different organelles with the help of diagrams. Prokaryotic and eukaryotic cells; Plant and animal cells. Difference between Prokaryotic and eukaryotic cells with the help of diagrams; Difference between plant and animal cells with the help of diagrams.

Tissue: (i) Plant Tissue and its Distribution: What is a tissue? How plant tissues can be classified into different types?
Concept of tissue as an organization level within a multicellular living body. Tissues are organizations of similar or different types of cells performing particular functions in a multicellular living body. Meristematic tissue: Characteristic features, distribution, and functions (with diagrams), Permanent tissue: Characteristic features, distribution, types, and functions in tabular form (with diagrams)

(ii) Animal Tissue: What are the bases of differentiation/classification of animal tissues?
Tissue types: Describing different animal tissues (epithelial, connective, muscular, and nervous) – distribution, structure, and functions of each tissue (with the help of diagrams in tabular form)

Major Organs of the Human Body and their Function: What is an organ? How do different organs play a vital role in the human body?
Concept of an organ: Explaining an organ with examples – Skin, stomach, pancreas, lung, heart, spleen, kidney, brain, spinal cord, testes, and ovary – position and their routes. Elucidating the positions of different organs with the help of diagrams/ real pictures and two functions of each organ (with diagram in tabular form)

Chapter 3 Physiological Processes of Life
Plant Physiology: (i) Photosynthesis: What is the fate of entrapped solar energy in the plant body?
Concept of Photosynthesis: Photosynthesis is a process where light energy, normally from the sun, is converted into chemical energy (that can later be released to fuel the organism’s activities). This chemical energy is stored in carbohydrate molecules, such as sugars, which are synthesized from carbon dioxide and water – The site of Photosynthesis. All chlorophyll-containing plant parts (examples) – Components of Photosynthesis and their role-CO₂, H₂O, sunlight and pigments chlorophyll and carotenoids. A brief outline of the roles of different components of photosynthesis; Explaining absorption and action spectra. Process: light-dependent phase and light-independent phase. A brief outline of major steps only Light-dependent phase: trapping of sunlight → activation of chlorophyll → photosynthesis of water → formation of end products of light-dependent phase (NADPH, O₂, and ATP); Light-independent phase: Fixation of CO₂ → formation of PGA → reduction of PGA → resynthesis of RuBP → synthesis of glucose (do not discuss the role of enzymes). Significance of Photosynthesis. Trapping and conversion of solar energy into food for plants and other organisms; O₂ – CO₂ balance.

(ii) Mineral Nutrition: How mineral nutrients are associated with the survival of plants?
Concepts of Macro-and Micro-nutrients with examples. Criteria for being qualified as macro-and micro-nutrients; Listing macro-and micro-nutrients; General functions of essential mineral nutrients; (e.g. formation of protoplasm, structure of enzyme, oxidation-reduction reaction, osmotic balance, formation of chlorophyll, buffer effect)

(iii) Transpiration: How do plants eliminate the excess water from their body?
Explanation: Elimination of excess water in the form of vapour; Comparing transpiration and evaporation – Sites of transpiration. Identifying the sites (stomata, lenticel, cuticular pore) – Factors controlling transpiration. Temperature, humidity, air movement, light, structure of leaf (leaf surface, cuticle, stomata) – Significance.  explain the significance (beneficial and harmful role).

(iv) Movement of Water, Food, and Gases: How different substances are transported in plant bodies?
Passive transport diffusion and osmosis – Features of diffusion and osmosis. Active transport – Elementary idea (lower to higher concentration, involvement of carrier molecule and requirement of energy) and examples – Cell to cell transport. Ascent of sap (role of root pressure and transpiration pull). Role of diffusion, osmosis, and active transport identifying the forces responsible for the movement of materials; Identifying, showing, and labeling the direction of flow of water; Recognizing the steps in the ascent of sap. Characteristic features of phloem transportation. Identifying showing and labeling the direction of the flow of food; Recognizing the steps in the translocation of food.

Respiration: (i) Organ level Respiration: Why Respiratory organs are so important?
Characteristic features of respiratory organs – Moist, extensive, and vascularized surface area – Respiratory sites of plants. Respiratory sites in plants – stomata, lenticels, pneumatophores – Respiratory organs of animals. Respiratory organs of animals – body surface, trachea(insect), gill(fish), lungs, and accessory respiratory organs (fish) – Lungs and breathing in humans. Inspiration, expiration, the role of the diaphragm and intercostal muscle; explaining with diagram the process of breathing (with the help of a working model of lungs) – Lungs and healthy life. Explaining in brief the role of breathing exercises and increased lung volume; cigarette smoking is harmful to the respiratory system.

(ii) Cellular Respiration: What is cellular respiration? In what way do different types of respiration differ from each other? How energy is utilized?
Concepts of cellular respiration. Oxidation of cellular substrate and production of energy; distinguishing respiration and combustion. Types of cellular respiration (Aerobic, Anaerobic, and Fermentation). Explain the occurrence, process of oxidation, and production of energy for each type of cellular respiration, the Steps of cellular respiration, and cellular sites where they occur. Mention the different steps of cellular respiration, i.e. Glycolysis → Krebs cycle → Terminal respiration. Signification of respiration, Mention cytoplasm and mitochondria as the sites. Liberation of energy and O₂ – CO₂ balance.

Nutrition: How do organisms process food inside their body?
Concepts of nutrition. Utilization of food for energy production, growth and repair, disease resistance – Types of nutrition. Plants: Explaining autotrophic and different types of heterotrophic nutrition (parasitic, symbiosis, saprophytic, and insectivory) with examples; Animals: parasitic, symbiotics, saprozoic, coprophagy, sanguinivory – Holozoic nutrition. Steps of holozoic nutrition and associated parts of the alimentary canal in humans. Alimentary system. Explaining the components of the dietary system and their role in nutrition; identifying, showing, and labeling parts of the alimentary system. Overview of digestion.

Mechanical and enzymatic digestion, hydrolysis – brief mention, hydrolysis, Digestive enzymes. Explaining the types with examples; site of secretion and their role in digestion (in tabular form); comparing and contrasting digestive enzymes. Absorption, Assimilation, and Egestion. Overview of absorption, assimilation, and egestion (site and process) – Metabolism. Explaining the fate of nutrients inside the cell; the brief idea of two types of metabolism with examples and mention significances, Dietary food intake, energy requirement, and associated problems. Concept of a balanced diet, BMR and its value; Calculation of energy required daily for an adult human; explaining metabolism-related problems in the human body.

Circulation: How different important substances are transported in the body of an organism? How is water utilized in the human body? Why blood is so important for human life?
Concept of circulation: Movement of nutrients, respiratory gases, metabolic wastes, synthesized substances, minerals, heat; Explaining components of the circulatory system of human blood, blood vessels, and heart, Types of circulation. Open and closed circulation with diagrams and examples of body fluids. Location and role of different body fluids-blood, lymph, sweat, urine, CSF, synovial fluid, tissue fluid, intracellular fluid, and Composition of blood (Plasma, Blood cell). Presenting composition of blood (with the help of chart); Plasma: Composition and functions; Blood cell (with the help of chart): origin, life span, and cellular characters of blood cells and their functions (in tabular form); Comparing and contrasting different blood cells with proper diagram, Blood group, and blood donation. Explaining the basis of grouping of blood (ABO & Rh factor); blood groups and significance (ABO incompatibility, Cross matching, Haemolysis). Misconception about blood donation. Coagulation of blood – Explaining coagulation of blood; factors involved (fibrinogen, prothrombin, tissue thromboplastin, calcium ion); major steps of the process and significance, Internal structure of human heart – Explaining chambers, valves, associated blood vessels, heart wall junctional tissues with the help of diagram or real pictures – Course of circulation of blood through heart – Explaining course of blood circulation through different chambers of heart; elementary idea of double circulation with diagram.

Excretion: How are metabolic wastes eliminated?
Concept of excretion: Explaining excretion (catabolism and production of harmful substances, their transport and elimination); outlining the water balance story of the human body and significance of excretion. Process of excretion in plants – Explain briefly the features of excretion in plants and processes (shedding of bark, leaves, and fruits with examples), Excretory products of plants. Nitrogenous and non-nitrogenous excretory products (tabular form) are excretory organs in animals. Contractile vacuole, flame cell, nephridia, malpighian tubule, kidney.

Excretory system of humans: Explaining, identifying, labeling, and analyzing the different parts of the excretory system of humans with the help of a diagram and their function – Nephron. Explaining and identifying structural components of nephron with the help of a diagram and their function; the role of the nephron in the formation of urine (ultra-filtration of blood, active reabsorption of ions, secretion of excretory substances, and passive reabsorption of water) – Accessory excretory organs of human. Explaining the roles of liver, lungs & skin.

Chapter 4 Biology and Human Welfare
Immunity and Human Diseases: How do human beings remain protected from disease-causing organisms? Who poses a threat to human health? How WASH can protect human beings from diseases?
Concept of immunity: Explaining the concepts of immunity, antigen, antibody, and immune response with a diagram. Concept of vaccine: Historical perspective – Edward Jenner and vaccination; different types of vaccine with examples. Pathogens and parasites causing human disease: Diarrhoea, malaria, diphtheria, pneumonia, tetanus, tuberculosis, dengue, Hepatitis A & B, AIDS (nature, symptoms, transmission) [In tabular form] Concept and components of WASH and its significance in eliminating disease burden – Developing knowledge and understanding about the importance of WASH and its impact on health and well being of human. Microbes in Human Welfare: How do microbes help us in our everyday lives?

• Bio-control agents – Explaining the role of bacteria, viruses, and protozoa.
• Bio-fertilizers – Explaining the role of bacteria, cyanobacteria, and mycorrhiza.

Chapter 5 Environment and its Resources
Ecology and Ecological Organization: What is ecology and how are the organisms organized in nature?
Ecology is the study of interactions between organisms and their environment including other organisms. In ecology interactions of organisms and their organizations are studied at the Individual level. Adaptation to light, humidity, and temperature with examples from the plant/animal world. Population-level: Concept of population and factors of population growth (natality mortality and migration). Community level: A Set of interacting populations is called a community and possible types of interactions among them are competition, predation, parasitism, and co-operation-explain with simple examples. Ecosystem level (Structural aspect): Abiotic factors: light, temperature, water, atmosphere, topography- mention only the names of different factors through the chart. Biotic factors communities including autotrophs and heterotrophs (consumers, decomposers, and transformers)-an elementary idea with examples with the help of diagrams, charts (Functional aspects): Explaining with examples- food chain, food web, energy flow, and nutrient cycle.

Natural Resources and its Sustainable Use: How different natural resources are intimately connected with our existence on earth?
Natural resources: forest, water, food, and energy – their use and overuse. Forest: Use (forest functions: watershed protection, atmospheric regulation, erosion control, local use, productive use); cause of deforestation and consequences. Water: Use (drinking, agriculture, industry, etc.); over-utilization and water scarcity (case study) Rainwater harvesting. Food: Source (Agriculture, horticulture, animal husbandry, fishery, alternate food sources); World food problem (case study) and its effect. Energy: Use, growing energy needs, wastage of energy/Energy conservation in daily life.

WBBSE Class 9 Life Science Blueprint for 3rd Summative Evaluation (Total Marks – 90)

Theme	Group A	Group B	Group C	Group D	Total Marks Per Theme	Total Number of Questions
	MCQ One Mark Per Question	VSA One Mark Per Question	SA Two Marks Per Question	LA Five Marks Per Question
Chapter 1 Life and its Diversity	1 × 3 = 3	1 × 3 = 3	2 × 2 = 4	5 × 1 = 5	15	9
Chapter 2 Levels of Organization of Life	1 × 3 = 3	1 × 4 = 4	2 × 3 = 6	5 × 1 = 5	18	11
Chapter 3 Physiological Processes of Life	1 × 3 = 3	1 × 5 = 5	2 × 3 = 6	5 × 2 = 10	24	13
Chapter 4 Biology and Human Welfare	1 × 3 = 3	1 × 4 = 4	2 × 2 = 4	5 × 1 = 5	16	10
Chapter 5 Environment and its Resources	1 × 3 = 3	1 × 5 = 5	2 × 2 = 4	5 × 1 = 5	17	11
Total	15	21	24	30	90	54

Group A – MCQ: All questions are compulsory. There will be no alternative for MCQ.
Group B – VSA: Out of 26 questions, 21 questions are to be attempted. One (1) extra question is to be set from each theme. VSA questions may be of four types – answer in one word or one sentence, fill in the blanks, true/false, and match column A with column B. In column matching two points are to be kept in mind – (i) For each correct matching one (1) mark is allotted, (ii) There should be at least one (1) extra option in Column B.
Group C – SA: Out of 17 questions, 12 questions are to be attempted. One (1) extra question is to be set from each theme.
Group D – LA: 6 questions are to be attempted. Alternative questions from the same theme are to be set for each question. 5 marks can be given as a whole or can be divided into 3 + 2 or 2 + 3.

WBBSE Class 9 Solutions

Comprehensive WBBSE Class 10 Physical Science Notes Chapter 8.6 Organic Chemistry can help students make connections between concepts.

Organic Chemistry Class 10 WBBSE Notes

Organic Chemistry : All carbon containing compounds except oxides of carbon, metal carbonates, bicarbonate, hydrogen cyanide and metallic cyanides are organic compounds and the chemistry of organic compounds is known as organic chemistry.

Organic compounds is a separate branch because organic compounds:

• are large in number
• show isomerism
• are soluble in non-polar solvents
• have complex structures
• are bad conductors
• show catenation
• are made from small number of elements.

Role of organic compounds in life process : Organic compounds are intemately related to our daily life. In order to maintain the life process of our body the following process are required.

• Intake of nutritional food for the growth the living body.
• For repairing the depreciation of health.
• Mobility
• Reproduction

All these are fulfilled almost by all organic materials.

(i) The main ingredients in our food chart are classified of three types : carbohydrates (e.g. rice, wheat, sugar etc.), proteins (e.g. milk, fish, egg etc.) and fats (e.g. milk, oil, butter etc.)

(ii) These food materials are ultimately converted to single organic compounds in different metabolic process with the help of enzymes in our body.

(iii) Vitamin, an organic compound plays indirectly a very important role for maintaining the growth of our health.

(iv) For the translation and mobility of the animals, energy which is required is stored in our body. This energy is associated in an organic compound. This is known as ATP (adenosine triphosphate).

(v) Haemoglobin which is an organic compound an oxygen carrier supplies oxygen in the body.

Biomoleculcs: The molecules of compounds like carbohydrates, amino acids, proteins, vitamins, fats, RNA, DNA etc. which are essential for the continuation of life processes of biological species like plants and animals (including human beings) are known as biomolecules.

Some essential biomolecules are :

(i) Carbohydrates : These molecules are composed of carbon, hydrogen and oxygen. General formula of it is C_n(H₂O)_n. Carbohydrates. are the class of compounds that include polyhydric aldehydes, polyhydric ketones and large polymeric molecules that can be broken down to polyhydric aldehydes and ketones.

Carbohydrates which contain aldehyde groups are called aldose and the carbohydrate containing keto groups are called ketose.

Carbohydrates are mainly of three types :

(a) Monosaccharides : These are the simplest form and are not hydrolysed, e.g. glucose, fructose etc.

(b) Oligosaccharides: During hydrolysis they form fixed number (2-10) of more saccharides.

(c) Polysaccharides: These are the natural polymer of large number of mono saccharides. It has general formula (C₆H₁₀O₅)_n. e.g. starch, cellulose etc.

(ii) Proteins: Another class of compounds essential for living being are proteins. They contain carbon, hydrogen, oxygen and nitrogen. Proteins are consumed daily from our diet. During hydrolysis of proteins by acid, base or enzyme amino acids are produced.
Proteins are of three types :
(a) Simple protein
(b) Conjugated protein
(c) Derived protein.

(a) Types of simple protein :

• Albumin: This type of protein can be isolated from egg, milk, wheat, serum etc.
• Globulin: Proteins that are isolated from egg yolk, tissues, belong to this class of protein.
• Glutemin: This type of protein is present in wheat, rice etc.
• Protamin: This type of protein is present in wheat, barli etc.

(b) Conjugated protein : Examples of this type of protein are : nucleo protein, chromoprotein, glycoprotein, phosphoprotein, lipoprotein, metalloprotein.

(c) Derived protein : This type of proteins are available by the partial hydrolysis of protein of very high molecular weight by acid, base or enzyme to simpler protein.

(ii) Fats: Fats are composed of carbon, hydrogen and oxygen. These are made of glycerol and fatty aids. Fats may be of animal or vegetable origin.

Animal fats are found in : milk, cheese, butter, eggs, meat and oily fish.

Vegetable fats are found in : walnut, almonds, groundnut and coconut, mustard seeds, seasame seed etc.

Fat is a concentrated source of energy.

(iv) Vitamins: Vitamins are organic compounds containing carbon, hydrogen, oxygen and sometimes nitrogen and sulphur. Vitamins are necessary to carry out many vital processes. Their absence or deficiency causes many ailments and impairs the healthy living oi human being.

(v) Amino acids: Proteins are made of amino acids. These are the essential for living beings. Amino acids are the class of compounds containing amino group and carboxylic acid group. 1

Amino acids are of three types :

Neutral amino acids : Amino acids containing the same number of amino and carboxylic acid groups are called neutral amino acids. These have one -NH₂ group and one -COOH group. Total number  of amino acids in this group is 19. e.g. glycine (NH₂CH₂COOH), alanin [CH₃CH(NH₂)COOH] etc.

• Basic amino acids : This type of amino acids have two -NH₂ groups and one-COOH group, e.g. lysine, histidine etc.
• Acidic amino acids : This type of amino acids have two -COOH groups ’• and one -NH_Z group, e.g. aspartic acid, glutamic acid.

The essential amino acids are :

• Valine
• Lucine
• Iso-lucine
• Phenylalanine
• Threonine
• Methionine
• Argenine
• Lysine
• Histidine
• Tryptophan.                                                                                                              ¹

DNA (Deoxyribo nucleic acids): It is found in nucleus, mitochondria and chloroplast of the body cells. James Watson and Francis Crick were able to establish the structure of DNA in 1953. DNA molecule is double helical in nature. It contains three different chemical compositions.

• Phosphoric acid
• Deoxy ribose
• Pyridine like base adenine and guanine, pyrimidine like base thymine and cytonine.

DNA has two strands of polynucleotides coiled around each other by hydrogen; bond in the form of double helix.

Function of DNA :

• Transmission of herediatary characteristics.
• Biosynthesis of proteins.

The genetic information for the cell is preserved in the sequence of this base in the DNA molecule. When a cell divides, DNA molecules replicate and make exact copies of themselves so that daughter cell will have identical DNA to that of parent cell.

RNA (Ribonucleic acid): RNA molecule is single stranded, containing 1 ribose, phosphoric acid and uracil as the nitrogenenous base. RNA plays a very Vital role in life process. RNA carries the message of DNA and acts accordingly.

Type of RNA : (a) mRNA (b) tRNA (c) rRNA. RNA(tRNA, mRNA) helps synthesis of polypeptides, the intermediates of proteins.

Bonding In organic compounds Electronic configuration of carbon shows that the number of electrons available in the outermost orbit is 4. The outermost electrons can only be capable to form covalent bond by sharing and pairing of its electrons with that of other element. So, valency of carbon becomes 4.

Catenation : The property by virtue of which carbon forms covalent linkage amongst them to form stable carbon chains is knoun as catenation. Catenation is an unique property of carbon. As a result of catenation, carbon can form innumerable chemical species with the supplement in various ways by the necessary addition of other elements like H, O, N, P, S, halogens etc.

Difference between organic and inorganic compounds :

Organic Compounds	Inorganic Compounds
(i) Catenation property of carbon atoms and its effect : The catenation property of carbon atoms among themselves and other atoms gives rise to limitless number of organic compounds with strain chains and rings of carbon atoms.	(i) Due to absence of catenetion property of its atoms, the number of inorganic compounds formed by the rest erf the elements in not so large.
(ii) Class similarity : Organic compounds can be easily classified into different groups with certain similar characteristic properties.	(ii) In organic compounds cannot generally be classified into such groups with similar characteristics.
(iii) Thermal stability : Organic compounds are in general, thermally unstable and decompose at higher temperature.	(iii) These are more or less thermally stable., These can tolerate comparatively higher temperatures without decomposition.
(iv) Bonding: Organic compounds are formed through covalent bonding in their molecules.	(iv) These compounds are generally formed by eledrovalent or ionic bonding in their molecules.
(v) Melting and boiling points: As these compounds are covalent in nature, so they have comparatively lower melting and boiling points.	(v) As these compounds are ionic in nature, so they have high melting and boiling points.
(vi) Solubility: These are soluble in organic solvents like alcohol, ether, benzene etc. but generally insoluble in water.	(vi) These are soluble in ionising solvents like water but are generally insoluble in organic solvents.
(vii) Structural characteristics: They have widely varying structural forms, from simple chain structure to complex ring.	(vii) They have mostly simple structure.
(viii) Isomerism: Different types of isomerism often occur in organic compounds.	(viii) Isomerism is practically unknown in inorganic compounds.
(ix) Electrolytic character: These are generally non-electrolytes	(ix) Inorganic compounds are general electrolytes.

Classification of organic compounds :

Functional group : The groups which are responsible to characterise the compounds are Known as functional group.

Homologous series : It is a group of compounds in which the various members have similar chemical properties, possess the same functional group and can be represented by the same general formula. The different members of a homologous series are called homologous and the phenomenon is called homology.

Constitutional or Structural Isomerism : The phenomenon in which two or more different compounds obviously having different physical and chemical properties possess the same molecular formula but different molecular structures due to the arrangements of the constitutional or structural isomerism.

Types of structural isomerism : Three types

(a) Chain isomerism; The compounds of the same class, with the same molecular formula, have chain isomerism due chain carbon atoms.

(b) Position isonierism : The compounds of the same dass, with the same molecular formula, have position isomerism due to the position of functional groups.

(c) Functional group isomerism : The compounds of the same class, with the same molecular formula, have functional group isomerism due to different functional groups.

Hydrocarbons : Hydrocarbons are organic compounds containing only carbon and hydrogen atoms in their molecules.

Types of hydrocarbons: Hydrocarbons are divided into two classes, namely

• Saturated hydrocarbons
• Unsaturated hydrocarbons.

Alkane : Open chain saturated hydrocarbons are known as alkanes. General formula of these compounds are : C_nH_2n+2 (n = integers)

Carbon atoms of these compounds are linked by single covalent bonds. Hy­drogen atoms of these compounds are also linked to one or more carbon atoms by a single covalent bonds.

Saturated hydrocarbon molecules do not contain any formal functional group and as such exhibit very little chemical activity. These are therefore known as paraffins.

Methane: Methane is the first member of the hydrocarbons of the alkane series. It is a colourless gas with molecular formula CH₄.

Source:

(ii) Main source of methane is the natural gas. It is formed in nature in bio­logical decay of plants of swamps and marshes. Methane is called marsh gas. A little phosphine (PH₃) and phosphorous dihydride (P₂H₄) accompany the methane gas and make it spontaneously inflammable. So, it often burns with flashes of flame over marshes. This is well known as ‘will-O-the-wisp’. It is just a natural phenomenon.

Chemical properties:
(i) Burning of methane: It burns in air or oxygen when ignited, and is oxidised to carbon dioxide and water with the evalution of heat.
CH₄+2O₂ = CO₂ + H₂O + 213 kcal/ molecule.

(ii) Substitution reaction : It undergoes substitution reaction. The first step of the reaction is :

Methane: A green house gas: Like carbon dioxide, water vapour etc. methane is known as a green house gas (contribution 19%) because it is capable to absorb visible light from sun-rays and keep the earth surface and its surrounding warm.

Uses of methane:

• It is used as a domestic and industrial fuel by burning in gas-stoves. Almost 40% by volume of methane is present in coal gas.
• It is used in the large-scale production of carbon black which is largely
  used for making printers’ ink, paints, typewriter, ribbon, motor tyres etc.
• It is now used as a source of hydrogen for the synthesis of NH₃.
• It is used for the manufacture of methanol, chloromethane, chloroform etc.

Alkene: An alkene is an unsaturated aliphatic hydrocarbon with a double bond in-between two adjacent carbon atoms of its molecule.

General formula of alkene : C_nH₄ (where n is an integer)

Ethylene [or, Ethene]
The molecular formula of ethylene is C₂H₄ which can be written as CH₂ = CH₂.
It i colourless gas.

Source :
(i)

(ii) It is present in very small amount in coal gas.
(iii) Natural gas rich in methane when ignited at 1400°C — 1500°C at normal pressure, acetylene is obtained after cooling.

Chemical reaction :
(i) Addition reaction with hydrogen:

(ii) Addition reaction with bromine :

Uses of acetylene :

• As an illuminant acetylene is used in acetylene lamp.
• It is used as an oxyacetylene flame 2700°C, for cutting and welding iron plates and sheets.
• It is used for the preparation of acetaldehyde, acetic acid, ethyl alcohol, acetone etc.
• Acetylene is used for the preparation of weston, a solvent used in industry.
• It is used for the preparation of synthetic rubber and plastics.
• It is used as an anaesthatic agent.

Polymer : There are some organic molecules of low molecular weight, a large number of which join with one another repeatedly to produce a very big molecule of high molecular weight. The small molecules are known as monomers and the resulting large molecules are known as p tymers.

Some common polymers :

Hazards of using polymer materials in our environment :

• Polythene, PVC, synthetic rubber after use are left anywhere else. Tyre used in the wheel of a vehicles are also thrown in the dustbin or these are burnt out. These materials have no natural decay in the soil by bacteria.
• As a result there is a dumping of plastic materials and creates an environ­ment pollution.
• It destroys the soils where it is dumping.
• The plastic materials left in hills and mountain, is the cause of landslide.
• Tyre prepared from synthetic rubber when left in air produces free radicals in presence of sunlight which is cancer producer.

Possible alternatives to avoid the hazards :

• To get relief from these, limited uses are desirable
• Now-a-day some reagents are added to plastic materials so that they would not create any problem or hazard to mankind.
• Bags made to cloth, paper, jute should be used instead of polythene bags.

IUPAC (International Union of Pure and Applied Chemistry, 1957) nomenclature simple organic compounds :

Polymerisation: The process or technique through which monomer units combine to give a polymer is known as polymerisation.

Biodegradable polymers : The polymers that can be dissociated into small segments enzymes (produced by microorganisms) are called biodegradable polymers.

Example :
(i) PHBV (poly β-hydroxy butyrate co-β-hydroxy-valerate)

LPG (Liquified Petroleum Gas) : In refinning the crude petroleum, the gaseous products thus obtained the hydrocarbons of lower molecular weight after purification of these gaseous mixtures if there are cooled at hith pressure and low temperature, these are all condensed to liquidand. The liquid is known as Liquified Petroleum Gas (LPG).

Types of LPG :

• Heavier grade LPG (80-90%) : C₄-hydrocarbon (Butane, Isobutane, butene)
• Lighter grade LPG (90%) : C₃ hydrocarbon (Propane and propene, 10% C₄-hydrocarbon (Butane and butene) 2% Ethane and ethylene.

Calorific value : Amount of heat energy produced by the complete com­bustion of one gram of the fuel is known as its calorific value.
Calorific value of LPG ; 29500 kcal/m³

CNG (Compressed Natural Gas):
It is compressed natural gas. It contains mainly methane. It has calorific value 21300 Btu/Ib

Uses of Ethanol:

• Ethanol (C₂H₅OH) is used for drinking purpose.
• Ethanol is widely used as a solvent.
• Ethanol burns of give carbon dioxide and water and thus can be used as fuel.
• Ethanol is used as antifreeze.

Physical properties of Ethanol :

• It is colourless liquid having a sweet smell.
• It is highly soluble in water.
• It is volatile and inflammable.
• It is neutral and it does not change the colour of litmus solution.

Reaction of Ethanol :

(i) Reaction with sodium (active metal): Ethanol reacts with sodium, to form sodium ethoxide and hydrogen.
2C₂H₅OH + 2Na → 2C₂H₅ONa + H₂↑

(ii) Reaction of ethanol with cone. H₂SO₄ for dehydration :
Ethanol reacts with cone. H₂SO₄ at about 170°C to form ethylene.

Uses of acetic acid (CH₃COOH)

• It is used as an aid in cooking and for making pickles as also a preservative of fish, meat, vegetable etc. as vinegar (6-8% water solution of acetic acid)
• It is used to prepare white paint.
• It is used to concentrate the latex of leather.

Reactions of acetic acid :

(i) Reaction of acetic acid with NaHCO₃ : During reaction of acetic acid with NaHCO₃, sodium acetate, carbon dioxide and water are produced.
CH₃COOH + NaHCO₃ → CH₃COONa + CO₂↑+ H₂O

(ii) Reaction of acetic acid with NaOH : Acetic acid reacts with NaOH to form sodium acetate and water.
CH₃COOH + NaOH → CH₃COONa + H₂O

(iii) Reaction of acetic acid with C₂H₅OH : This reaction is called esterifi­cation. During this reaction ethyl acetate and water are produced.

Toxicity of Methanol : Methanol has a high toxicity in human. If as little as 10 mL of pure methanol is ingested, for example, it can break down into formic acid, which can cause permanent blindness by destruction of the opti nerve and 30 mL is potentially fatal, although the median lethal dose is typically 100 mL. Toxic effects take hours to start and effective antidotes can often prevent permanent damage.

Methanol is toxic by two mechanisms. First methanol (whether it enters the body by ingestion, inhalation or absorption through the skin) can be fatal due to its CNS depressant properties in the same manner as ethanol poisoing. Second, in a process of toxication, it is metabolized to formic acid (which is present as the formate ion) via formaldehyde in a process initiated by the enzyme alcohol dehydrogenase in the liver.

Methanol is converted to formal­dehyde via alcohol dehydrogenase (ADH) and formaldehyde is converted to formic acid (formate) via aldehyde dehydrogenase (ALDH). The conversion to formate via ALDH proceeds completely, with no detectable formaldehyde remaining.

Formate is toxic because it inhibits mitochondrial cytochrome C oxides, causing the symptoms of hypoxia at the cellular level, and also caus­ing metabolic acidosis, among a variety of other metabolic disturbances. So methanol is highly toxic and causes blindness insanity and even death. Ethanol is non-toxic but when drunk, it produces physiological effect and disturbs the brain activities.

Denatured spirit : Alcohol used for making beverages is highly taxed but the ethyl alcohol supplied to the chemical laboratories and industries is very cheap.

To make it unfit for drinking purposes, industrial alcohol is mixed with poisonous substance like methanol, pyridine etc. The process is known as denaturing and the product is called denatured alcohol. The ethylalcohol mixed with the methanol is called methylated spirit.

Comprehensive WBBSE Class 10 Physical Science Notes Chapter 8.5 Metallurgy can help students make connections between concepts.

Metallurgy Class 10 WBBSE Notes

Occurrence of metals : A few metals particularly noble metals (Au, Pt, Ag etc.) having least electropositive charader occur in free state. About 75% of the known elements are metals. Most of the metals are found in the combined state in nature as their compounds.

Minerals : The natural materials containing metals and their compounds associated with earthy and other impurities found under earth’s crust are called minarals.

Ores : The minerals from which the metals can be extracted conveniently and profitably. All ores are minerals but all minerals are not ores.

Metallurgy : It is a process of extracting metals from their ores.

Gangue or Matrix: They are the rocky and earthy impurities associated with the minerals.

Concentration of ore : It is the process of removal of gangue from the ore.

Flux: It is the substance which combines with gangue to form light and easiÍilusible material called slag.

Slag : It is the light and fusible material obtained by the combination of flux with gangue.

Calcination : It is the process of heating an ore in a limited supply of air or in absence of air at a temperature just below its melting point.

Roasting : It is the process of heating an ore in a limited supply of air or in absence of air at a temperature just below its melting point.

Extraction of metal : Different processes that are used for the extraction of pure metals from ores are called extraction of meials;

Alumimium (AI)

Symbol: Al; Valency : 3;
Atomic weight: 26-78
Atomic Number: 13,

Position in Periodic Table:
Period: 3, Group IIIA (13);
Electronic configuration : ls²2s²2p⁶3s²3p¹

Occurrence: Aluminium is not found in pure state. It occurs to the extent of 8% in earth’s crust in many silicate rocks and clays. It is the third most abundant element in the earth’s crust.

Important aluminium minerals are :

• Chief ore of aluminium : Chief ore of aluminium is bauxite (Al₂O₃-2H₂O).
• Mines : In India, large quantities of bauxite are available in Bihar, Jharkhand, Orissa, Andhra Pradesh, Madhya Pradesh, Rajasthan, Tamilnadu, Gujarat and Jammu-Kashmir. But large deposit of quality grade bauxite are found in Andhra Pradesh.
• Extraction of aluminium : Initially alumina is prepared from bauxite then after mixing with cryolite and fluosper aluminium is extracted by electrolysis at about 950°C
  
• The ore of aluminium (bauxite) is purified by Baeyer’s process, Hall’s process or Serpeck’s process depending upon the type of impurities present in it. Baeyer’s process or Hall’s process is used for ores containing oxides of iron as main impurity while Serpeck’s process is used for ores containing silica as main impurity.

Physical properties of Aluminium :

• It is silvery white metal and is very light, (sp.gr. = 21)
• It melts at 660°C and boils at 2270°C.
• It is a good conductor of heat and electricity.
• It is malleable and ductile.
• Atomic radius of aluminium is 125 pm.
• The ionisation enthalpies of Aluminium are 600 KJ mol^-1, 2427 KJ mol^-1 and 3568 KJ mol^-1
• Sum of the first three ionisation enthalpies being very high, aluminium forms covalent compounds.

Chemical Properties :

(i) Action on

• Dry air has no action on aluminium. In moist air, it forms a thin film of oxide on its surface.
• When heated strongly, it burns with a brilliant white light, producing aluminium oxide and little nitride.

(ii) Action of water : Pure water has no effect on the metal due to the presence film on the surface. Amalgamation with mercury prevents the protective oxide film. Amalgamated metal, therefore, can decompose even cold water. Commercial aluminium can be readily attacked by sea water. It decomposes boiling water, liberating hydrogen. 2Al + 6H₂O = 2Al(OH)₃ + 3H₂

(iii) Action of chlorine : when aluminium is heated gently with chlorine, it forms aluminium chloride.
2Al + 3Cl₂ = 2AlCl₃
A mixture of aluminium powder and iodine catches fire when a drop of water is added on it.

(iv) Action of acids: (a) With dilute sulphuric acid, hydrogen gas is evolved at a slow rate. In hot concentrated sulphuric acid, metal dissolves with the evolution of
2Al + 3H₂SO₄ (dilute) = Al₂(SO₄)₃ + 3H₂
2Al + 6H₂SO₄ (cone) = Al₂(SO₄)₃ + 3SO₂ + 6H₂O

(b) With dilute nitric acid, aluminium nitrate and ammonium nitrate are produced.
Action with carbon Sulphur :
8Al + 3OHNO₃ = 8Al(NO₃)₃ + 9H₂O + 3NH₄NO₃

(v) Action with carbon and sulphur :
Aluminium reacts with boiling caustic soda or caustic potash forming sodium aluminate or potassium aluminate respectively with the evolution of hydrogen gas.

(vi) Action of alkalls: Aluminium reacts with boiling caustic soda or caustic potash forming sodium aluminate or potassium aluminate respectively with the evolution of hydrogen gas.
2Al + 2NaOH + 2H₂O = 2NaAlO₂ + 3H₂↑
2M + 2KOH + 2H₂O = 2KAlO₂ + 3H₂↑
That is why, caustic soda is not boiled in aluminium pot.

(vii) Displacement reactions: Aluminium is strongly electropositve. Hence, it readily displaces less electropositive metals, such as-murcury, silver, gold etc.
2Al + 3HgCl₂ = 2AlCl₃ + 3Hg.

(viii) Peducing property: Due to its strong affinity of oxgen it acts as a strong reducing agent. It readily reduces certain metallic oxides to the metal.

These reactions are highly exothermic and they can be utlised for welding (Thermite welding) of metals.

Uses of Aluminium:
At present, use of aluminium is just after iron.

• Being a light material as also stable and resistance to water vapour it is used to prepare external structures of air-ships and motor cars.
• It is used in electric wire and electric equipments as it is a very good conductor of electricity.
• It forms many useful alloys used for different purposes. Alloys like dural­umin, magnelium bronze etc. and also in flash bub used in photography aluminium metals are used.
• Aluminium is used in thermit process. Due to its strong affinity for oxygen, it is used for the extraction of metals like Cr and Mn from their ores.
• Mixed with linseed oil, powdered aluminium is used as paint.
• Ammonal, a mixture of ammonium nitrate and aluminium powder, is used in explosive bombs.
• Aluminium power has the use in fireworks.
• Aluminum is used in the preparation of different utensils, chair, table and the packing over a cigarette, coffee, chocolate etc.

Artificial gem are produced by dropping powdered alumina mixed with little of other metallic oxides to obtain desired colour (e.g. 2-5% chromic oxide for artificial ruby). Sapphire is similary produced from alumina with addition of a little magnetic iron oxide and titanium oxide.

Foods having sour taste should not be preserved in aluminium foil, since fatty acid present in those types of foods react with aluminium foil producing salts which are very harmful to health.

Magnesium (Mg)

Symbol: Mg ; Valency: 2 ; Atomic weight: 24
Atomic Number: 12 :
Position in Periodic Table :
Period: 3; Group: IIA (2) :
Electronic Configuration : Is²2s²2p⁶3s²
Occurrence: Magnesium is not found in free state in nature.

Important magnesium minerals are :

Nature	Minerals
1. As carbonates	Magnesite : MgCO3 Dolomite : MgCO, CaCO
2. As chloride	Carnallite : MgCl2 . KCl . 6H2O
3. As sulphate	Kieserte : MgSO4 . H2O Kainite : MgSO4 – KCl- 3H2O Epsom Salt : MgSO4– 7H2O
4. As silicate	Asbestos: CaMg3 (SiO3)4

Chief ore: Magnesium is extracted from the ores magnesite and carnallite. Magnesium metal is also found in sea-water, chlorophyll and also in sping.

Mines : The chief ore of magnesium is carnallite. But carnallite is not available in India. It is imported from Germany, where it exists as deposits at stassfurt. Other important ores of magnesium are magnesite and dolomite which are abundantly available in Tamilnadu, Karnataka and in many parts of Bihar, Jharkhand, Orissa, West Bengal and Sikkim.

Extraction: Magnesium is prepared by:

• Electrolytic reduction of the fused magnesium chloride.
• Chemical reduction of MgO by carbon or ferro-silicon.

Physical properties of magnesium:

• Magnesium is a light, white metal with a bright lustre which tarnishes in moist air due to the deposition of a film of oxide.
• Soft, malleable, and ductile, it can be readily drawn into a wire of ribbon.

Chemical properties:
(i) Action with air: Mg does not react with dry air. If magnesium metal is left in moist air it gradually becomes dull and pale due to the formation of a layer of MgO. Magnesium metal when heated in presence of air it burns with bright white flame. Magnesium oxide and magnesium nitride are thus formed.
2Mg + O₂ = 2MgO ; 3Mg + N₂ = Mg₃N₂

(ii) Reaction with water (a) At ordinary temperature Mg metal does not react with water, (b) Heated Mg burns in presence of water vapour magnesium oxide and hydrogen are formed.
Mg + H₂O = MgO + H₂↑

(iii) Reaction with dilute nitric acid: It dissolves in dilute nitric acid, liberating hydrogen, but not in alkalis.
Mg + 2HNO₃ = Mg(NO₃)₂ + H₂↑

(iv) Mg acts as reducing agent. It is a powerful reducing agent; the heated metal reduces such stable oxides as silica, sodium oxide and potassium oxide. Ignited magnesium continues to burn in CO₂ depositing carbon.

(v) Reaction with chlorine Heated magnesium burns in chlorine and form magnesium chloride.
Mg + Cl₂ = MgCl₂

Uses of magnesium : It is used

• In flash light powders (magnesium powder mixed with potassium chlorate or barium peroxide) for photography, in military star shell, in light signals and in fire works.
• for the preparation of Grignerd reagent in organic chemistry and for reducing agent.
• In the production of light alloys, such as-duralumin, magnelium in the construction of airships and motor cars.
• In incendiary explosive (goop is an incendiary containing magnesium powder).
• In the extraction boron and silicon.

Zine (Zn)

Symbol : Zn ; Valency : 2; Atomic weight: 65.3
Atomic Number : 30;
Position in Periodic Table;
Period: 4, Group : IIB (12);
Electronic Configuration : ls²2s²2p⁶3s²3p⁶3d¹⁰4s²

Occurrence : Zinc does not occur free in nature. In the combined state, it occurs in the form of following minerals.

Nature	Minerals
1. As sulphide	Zinc blende : ZnS
2. As oxide Franklinite : ZnC	Zincite : ZnO,Fe2O3
3. As carbonate	Calamine : ZnCO3
4. As silicate	Willemite : Zn2SiO4

Chief ore: The most important source of zinc is zinc hiende, usually containing about 6% Zn.

Mines: Zinc blende is obtained from zawar at Udaipur (Rajasthan) in India. Calamine is obtained at smithsonite in the U.S.A.

Extraction: Zinc is extracted mostly from zinc blende. The zinc blende which invariably contains so me galena in concentrated by oil floating process. Zinc is obtained from the zinc concentrate either. (a) by the carbon reduction process (b) by the electrolytic process.

• Physical properties of zinc:
• It is a bluish white solid which melts at 420°C and boils at 920°C.
• Its density is 7-14 g/c.c.
• It is a good conductor of electricity.

Chemical properties of zinc :

(i) Action of air: It burns in air with a green flame, if strongly heated, forming white clouds of zinc oxide which settles in wooly flocks (philosopher’s wool) 2Zn + O₂ = ZnO

(ii) Action of water Pure zinc has no action of water. Impure zinc decomposes boiling water. Zn-Cu couple decomposes water producing hydrogen gas.
Zn + 2H₂O = ZnO + H₂↑

(iii) Action of chlorine and sulphur Zinc reacts with chlorine forming zinc choride with sulphur, zinc sulphide is formed.
Zn + Cl₂ = ZnCl₂
Zn + S = ZnS

(iv) Reactions with acids :
(a) With HCl : Zn + 2HCl (dilute) = ZnCl₂ + H₂↑
(b) With H₂SO₃ :
(i) Zn + H₂SO₄ (dilute) = ZnSO₄ + H₂↑
(ii) Zn + 2H₂SO₄ (cone.) = ZnSO₄ + SO₂ + 2H₂O
Action with alkalis:
Zinc dissolves in hot solutions of caustic soda and potash, yielding hydrogen and zincate.

(vi) Displacement of less electropositive metals :
When zinc is added to the salt solution of a less electropositive metal like copper, silver, the metal is displaced.
CuSO₄ + Zn = ZnSO₄ +Cu ↓
2AgNO₃ + Zn = Zn(NO₃)₂ + 2Ag ↓

Uses of zinc : It is used:

• For galvanisation of iron sheets because zinc is resistant to atmospheric corrosion due to the formation of basic carbonate on its surface.
• In the extraction of silver and gold by cyanide process.
• as a cathode in dry cells.
• zinc is used for the preparation white paint zinc oxide (ZnO).
• for the preparation of hydrogen in the laboratory.
• in the preparation of alloys such as brass, german silver, etc.

Iron (Fe):

Symbol: Fe ; Valency : 2, 3; Atomic weight: 55-85
Atomic number: 26 ;
Position in Periodic Table :
Period : 4, Group VIII(8);
Electronic Configuration : 1s² 2s²2p⁶3s²3p⁶3d⁶4s²

Occurrence : Iron is not obtained in free state. Next to aluminium, iron is the most abundant metal in the earth’s crust. Compounds of iron occur in the soil, in green plants and in haemoglobin (0-336% Fe) the red colouring matter of blood.

Meteorites sometimes consist of iron with (3 -30)% of Ni; because of its nickel content meteoric iron does not rust readily.

The chief minerals of iron are given below :

Nature	Minerals
1. As oxide Brown Haematite: Magnetite: Fe3O4	Red Haematite: Fe2O3 2Fe2O3. 3H2O (Limonite)
2. As sulphide	Iron pyrites: FeS2
3. As carbonate (Siderite)	Spathic iron ore: FeCO3

• Chief ore : Iron is extracted mainly from the ore Haematite an<-’ magnetite may be used.
• Extraction : Iron is extracted from its oxide and carbonate ores (burnt pyrites which is chiefly ferric oxide, is sometimes used) by reduction with carbon in a blast furnace.
• Mines : Rich deposits of good quality haematite are available in many parts of India, such as in Orissa, Bihar, West Bengal, Tamilnadu, Karnataka, Andhra Pradesh and Madhya Pradesh.

Physical properties of iron :

• Pure iron is silvery white lustrous metal resembling platinum in appearance. It can take high polish.
• It is malleable and ductile and good conductor of heat and electricity.
• It is relatively soft and possesses high tensile strength.
• It is the most magnetic of all metals but loses this property above 760°C.
• Iron melts at 1525°C, boils at 2450°C and its density is 7-86 g cm^-3.

Chemical properties :

(i) Action of water : Iron decomposes steam to liberate hydrogen. This reaction is utilized for the manufacture of hydrogen. 3Fe + 4H₂O = Fe₃O₄ + 4H₂↑

(ii) Action of moisture : When exposed to moist air, iron gets covered with a reddish yellow film. This is known as rust and the phenomenon is called rusting. The composition of rust is 2Fe₂O₃. 3₂O. Rusting is formed when iron reacts with oxygen and water vapour.

(iii) Action of water : Iron decomposes steam to liberate hydrogen. This reaction is utilized for the manufacture of hydrogen. 3Fe + 4H₂O = Fe₃O₄ + 4H₂↑

(iv) Action of halogens and sulphur

(v) Displacement of less electropositive metals: It displaces less electropos­itive metals like copper from their salts. CuSO₄ + Fe = FeSO₄ + Cu₄↓

(vi) Reaction with alkalis : It has no reaction with alkalis.

(vii) Action of acids :
(a) Fe + H₂SO₄ (dilute) = FeSO₄ + H↑
(b) Fe + 2HCl (dilute) = FeCl₂ + H₂↑
(c) 4Fe + 10HNO₃ (dilute) = 4Fe(NO₃)₂ + NH₄NO₃ + 3H₂O
(d) (i) Fe + 2H₂SO₄ (cone.) = FeSO₄ + SO₂ + 2H₂O
(ii) 2FeSO₄ + 2H₂SO₄ (cone.) = Fe₂(SO₄)₃ + 2H₂O + SO₂

(viii) Passivity of iron: Fairly strong nitric acid gives ferric nitrate and a mixture of oxides of nitrogen. However, cone., nitric acid makes iron passive i.e. it becomes chemically inert and does not react further.

Uses of iron :

• Iron is widely used for making beams, rafters, rods for building and for con­structing ships, submarines, rails and rail-wagons.
• It is also used for preparing nuts, bolts, screws, wires, covers of drains, rain water pipes and pipes for conveying drinking water etc.
• It is also used to make ordinary steel and alloy-steels.

Iron is classified according to quantity of carbon present:

(i) Cast iron : (2-4)% carbon and small amount of silica, Mn, R S etc are present in iron. use: (t is used for the manufacture of railings, drain pipes, radiators, gutters.

(ii) Wrought iron : Smallest quantity of carbon is present in it. Iron of this type contains (01- 015)% of carbon. use: It is used for the manufacture of nails, chair, anchors, horse shoes.

Steel : In steel (0-15- 1-5)% and small quantities of silicon, Mn are mixed with iron. use: It is used for the manufacture of car wheel springs razor blades, ma­chine parts, ships, opera­tion equipments, building structures and arms.

Copper (Cu)

Symbol: Cu; valency : 1, 2; Atomic weight: 63-5
Atomic number : 29 ;
Position in Periodic Table :
Period : 4, Group IB(ll) ;
Electronic Configuration : ls²2s²2p⁶3s²3p⁶3d¹⁰4s¹

Occurrence : Copper occurs in minute quantities in plants, particularly in green peas. It is present in the haemocyanin of blood cuttlefish, which acts like haemoglobin as an oxygen carrier. Copper helps in the formation of haemoglobin in the body. Lower organisms are very sensitive to copper salts and hence their use as fungicide, copper exists in small amount in free state in nature. The chief minerals are :

Nature	Minerals
(i) As oxide	Cuprite : Cu2O Malaconite : CuO
(ii) As sulphide	Chalcocite (copper glance): Cu2S Chalcopyrite (copper pyrites): Cu2SFe2S3
(iii) As carbonate	Malachite : CuCO3–Cu(OH)2 Azurite : 2CuCO3 Cu(OH)2
(iv) As chloride	Attacamite : CuCl2 . 3Cu(OH)2

Chief ore: Copper is mainly extracted from copper pyrities.

Mines: The chief copper-producing regions are : Montana, Ariz una, Canada, Japan, Russia, Germany, Cango, Spain and Chile. India is not rich in copper ore. In India, copper pyrites is available in small amounts in Singhbhum, Bihar, Tamilnadu, Karnataka, Uttar Pradesh, Sikkim, Orissa.

Extraction of copper from copper pyrities :

• crushing
• concentration by froth floatation
• roasting
• smelting with coke and sand in a blast furnace
• best merization of molten matte obtained from blast furnace to get blister copper.
• purification by electrolytic process.

Physical properties of copper :

• It is a reddish brown metal.
• It is highly malleable and ductile.
• Copper melts at 1083°C and boils at 2323°C
• Copper is a quite heavy metal (density 8.94g/cc )
• It is an extremely good conductor of heat and electricity.
• It readily forms alloys.

Chemical properties of copper :

(i) Action of air: (a) Dry air has no effect on copper metal. However, when it is exposed to damp air for a long time, a green coating of basic copper carbonate. CaCO.Cu(OH)₂ is formed on its surface.

(b) When heated with air, copper forms cupric and cuprous oxides.

(ii) Action of Water (and even stearia) has no action on copper. How ever, at very 1 temperatures (at white heat), it is attacked by steam when slight oxidation takes place.

(iii) Action of acids on copper:

(iv) Reaction with chlorine and sulphur:

(v) Reducing properties:

Displacement reactions: Copper displaces less electropositive metal like silver, gold, platinum and mercury from their salts.
Cu + 2AgNO₃ = Cu(NO₃)₂ + 2Ag
3Cu + 2AuCl₃ = 2Au + 3CuCl₂

(vi) Action with cyanides: It also dissolves in an aqueous solution of potassium cyanide yielding the complex, [Cu(CN)₄]^2-

(vii) Formation of colloidal copper : On striking an ore between two copper electrodes immersed in water, a dark red colloidal solution of copper is obtained.

Uses of copper :

• Due to its very high electrical conductivity it is largely used for telegraph and telephone, and also for electrical machinary.
• Copper is not attacked by air or water. So, it can be used for making household utensils, and water pipes.
• It is used in electroplating and electrotyping and in coinage.
• It is used in making a number of useful alloys.
  e.g. Brass: Cu (60-80)%, Zn (40-20%); Bronze: Cu (75-90)%, Sn (25-10)%

Alloy : It is homogeneous mixture (or, sometimes, a heterogeneous combination) of two or more metals, behaving as single metal in most of its physical properties.

Alloy is formed not only combination metals alone but also many non-metals viz. C, Si, S, P are added to prepare alloys.

Amalgam : If one of the component metals of an alloy be mercury, it is termed as amalgam, e.g. sodium amalgam (Na/Hg), aluminium amalgam (Al/Hg) etc.

Advantages of using alloys over pure metals :

• Increase of hardness: as in gold for ornaments, high speed steel etc. N.B. Pure gold is somewhat soft. It is made harder by alloying with a little amount of Cu or Ag.
• Increase in resistance to corrosion: as in stainless steel.
• Increase in strength: as in steel, duralumin etc.
• Increase of resistance to electricity: as in nichrome.
• Increase in fusibility or decrease in melting point : as in solders, fuse wires etc.
• Betterment of appearance . as in aluminium bronze, stainless steel etc.
• Improvement of casting property : as in type metal.
• Change in chemical activity : as in sodium amalgam, zinc amalgam etc.

Some important alloys :

Comprehensive WBBSE Class 10 Physical Science Notes Chapter 7 Atomic Nucleus can help students make connections between concepts.

Atomic Nucleus Class 10 WBBSE Notes

Atom and its constituents:

Inventor	Sub-atomic particles
J.J. Thomson (1897)	Electron
E. Rutherford (1911)	Proton
J. Chadwick (1932)	Neutron
Anderson (1932)	Positron
Yukawa (1935)	π – meson
Name given by Fermy (1956)	Neutrino

Nucleus : From Rutherford’s experiment on scattering of α-particles, it was established that the positive charge of an atom and almost whole of its mass must be concentrated in a small region (10^-12 -10^-13cm) & (while dimensions of atoms 10^-8cm)
Atomic number: The number of protons in the nucleus is called the atomic number of atom.
Mass number: The sum of the number of protons and neutrons is called mass number.
Nucleons : The protons and neutrons are collectively known as nucleons.
Nuclear reactions : Nuclear reactions are the reactions in which nucleus of an atom undergoes a change.
Nuclear chemistry: The branch of chemistry which deals with the phenomenon of nucleus of atoms is known as nuclear chemistry.

Type of species :

(i) Isotopes: The atoms of an element having same atomic number but different mass number are called isotopes.

(ii) Isobars : The nuclides of different chemical elements having same mass number but different atomic numbers are called isobars.

(iii) Isotones: The nuclides of different chemical elements having the same number of neutrons but different atomic numbers are called isotones.

(iv) Nuclear isomers : The nuclear species having same atomic number and same mass number but different radioactive properties are called isomers or nuclear isomens.

Examples:

(v) Isodiaphers : Atoms having the same isotopic number or isotopic excess (number of neutrons-number of protons) are called isodiaphers.

Examples : \(\quad{ }_{92}^{238}\) U and \({ }_{90}^{234}\) Th

(vi) Isoster : Molecules or ions with same number of atoms and also the same number of electrons are said to form isosteric group or more simply isosters.

Examples : In N₂ O and CO₂;
number of electrons = 22. So, they are isosters.

Radioactive radiations :

Characteristics of alpha (α), beta (β) and gamma (γ) – rays.

Stability of Nucleus : The stability of the nucleus is decided by the following factors:

(a) Nuclear forces: The forces which held the nucleons together within the small nucleus are called nuclear forces.
These force exist among p-p, p-n and n-n.

Nuclear force has been explained by yukawa by the discovery of a new fundamental particle called π-meson
These may be denoted as π⁺, π^– and π⁰

The mesons keep on exchanging among the nucleons very rapidly (about 10²⁴ transfers per second) and hold the nucleons together.

All nuclei with 84 or more protons i.e. atomic number ≥ 84 are unstable.

(b) Mass defect : Δm, the difference between the experimental and calculated masses of the nucleus is called the mass defect.

(Experimental mass of nucleus) – (mass of proton + mass of neutron) = mass defect.

(c) Binding energy: Atomic nucleus is made of protons and neutrons closely in a small volume. Although there exist intensive repulsive forces between the component protons, the nucleus is not slit apart. This is so because the nucleons are bound to one another by very powerful forces. The energy that binds the nucleons together in the nucleus is called the nuclear binding energy.
The binding energy of a nucleus can be calculated from its mass defect by using Einstein’s equation,
Δe = Δ m × c² or Binding energy = Δm × 931 MeV

By plotting the binding energy per nuclear against the mass number, we get the graph shown in figure below.

(d) Packing fraction : Packing fraction was proposed by Aston and defined as the difference of actual isotopic mass and the mass number.

Packing fraction =\(\frac{\text { (acutal isotopic mass-mass number) }}{\text { mass number }} 10^4\)

The value of packing fraction may be negative, positive or zero. A negative packing fraction indicates less stability of nucleus. In general, for lower packing fraction the binding energy will be greater and the nucleus will be more stable.

(e) Neutron-Proton ratio (N / P ratio) : The stability of a nucleus seems depend on the neutron to proton (n / p) in the nucleus.

(i) In lower elements (upto z=20 ), the stable nuclei have about equal number of protons and neutrons i.e. \(\frac{n}{p}\) = 1
(ii) For higher elements to be stable, there must be more neutrons than protons i.e. \(\frac{n}{p}\) >1.
(iii) The shaded portion in figure represents the region or belt of stability. The elements whose n / p ratios lie inside the belt are stable.
(iv) A nucleus whose n / p lies above or below the stability belt is radioactive or unstable on account of unfavourable n / p ratio. It emits α or β-particles so as to move into the stability range.

Know more :
(a) If \(\frac{n}{p}\) > 1 to 1.5 i.e. it places above the stability belt. Such nuclei emit- β particle in order to lower its \(\frac{n}{p}\) ratio

(b) If \(\frac{n}{p}\) < 1 to 1.5 i.e. places below its stability belt, such nuclei either emit positrons or undergo electron capture.

(c) The even odd nature of the number of protons and neutrons : The number of stable nuclides is maximum when both p and n are even number. However, the number of stable nuclides in which either the z(p) or n is odd is about one third of those where both are even.

The magic numbers : Magic numbers are the numbers 2, 8, 20,50, 82 and 126. Nuclides having magic number of either proton or neutrons or both are more stable. Nuclides with atomic numbers equal to magic numbers have more number of stable isotopes than their neighbours. Nuclides having even number of protons and neutrons are more stable than nucli containing odd number of these particles.

Radioactivity : It is a process in which nucleus of certain elements undergo spontaneous disintegration without excitation by any external means. This phenomenon was first discovered by Henry Becquerel (1866). However, the term radioactivity was proposed by Madam Curie.

Group Displacement Law (Fajans and Soddy in 1913) : We know that an α-emission decreases the atomic number of the parent by 2 and β emission increases the atomic number by 1 .
Thus ‘In an α emission, the parent element will be displaced to a group two places to the left and in β emission, it will be displaced to a group one place to the right’.

Disintegration Series : The whole series of elements starting with the parent radioactive element to the stable end product is called a radioactive disintegration series.

Radioactive Decay: If N be the number of undecay atoms of an isotope present in a sample of the isotope, at time t, then

\(\frac{-d N}{d t} \alpha N\)
or, \(\frac{-d N}{d t}=\lambda N\)

where, \(\frac{-d N}{d t}\) tmeans the rate of decrease in the number of radioactive atoms in the sample and λ is the proportionality constant. This is known as disintegration constant.

Disintegration constant : It may be defined as the proportion of atoms of an isotope decaying per second.

Various forms of equation for radioactive decay are :

(i) N_t = N₀ e_-λt
(ii) λ = \(\frac{2 \cdot 303}{t}\) log \(\frac{N_0}{N_t}\)
(N₀= No. of atoms initially
N_t = No. of atoms after time t)

Half-Life period : Half-life period of a radioactive isotope is the time required for one-half of the isotope of decay.

t_1/2 = \(\frac{0.693}{\lambda}\)

The value of λ can be found experimentally be finding the number of disintegrations per second with the help of a Geiger-Muller Counter.

The unit of half life period : time^-1

Average life : The statistical average of the lives of all atoms present at any time is called the ‘average life’.

τ = 1.44 × t_1/2
(τ = Average life
τ = \(\frac{1}{\lambda}\))

Activity of a Radioactive Substance :

• Higher is the activity of a substance, faster will be its disintegration and vice-versa.
• The greater the half-life of the substance, lesser is its activity and vice-versa.
• The activity of a radioactive sample is usually determined experimentally with the help of a Gieger Muller counter.

Radioactive Equilibrium : Radioactive change being an irreversible process shows equilibrium when a daughter element disintegrates at the same rate at which it is formed from parent element.

Unit of Radioactivity :

• Curie : If a radioactive substance disintegrates at the rate of 3.7 × 1010 disintegrations per second, its activity is said to be 1 curie.
• Rutherford : If a radioactive substance has 106 disintegrations per second, it is said to have an activity of one Rutherford.
• Becqurel (SI unit) : If a radioactive substance has 1 disintegration per second, it is said to have an activity of one Becquerel.

Measurement of Radioactivity : The instruments used are

• Geiger-Muller counter
• Wilson cloud
• Electroscope

Natural transmutation : It is a process in which elements such as radium undergoes transmutation on their own.

Artificial transmutation: It is the process in which a stable nuclei is changed into another by artificial methods i.e. by bombarding the target nuclide with projectiles such as α-particles, neutrons etc.
The first artificial transmutation was carried out by Rutherford (1919) by bombarding nitrogen with α-particles.

Artifical radioactivity : It is the phenomenon in which artificial transmutation of a stable nucleus leads to the formation of a radioactive nuclide.

Contributions of Artificial Transmutation : The following are the important contributions of artificial transmutation :
(i) Discovery of neutron
(ii) Artificial radioactivity
(iii) Nuclear fission
(iv) Nuclear fusion

Alchemy : The process of transforming one element into other is known as alchemy and the person involved in such experiments is called alchemist.
Nuclear reaction: It is a reaction in which the number of protons in the nucleus of an element changes to form a new element.

Difference between Nuclear and Chemical Reactions :

Nuclear reactions	Chemical reactions
(i) Proceed by distribution of nuclear particles.	(i) Proceed by the rearrangement of extra nuclear electrons.
(ii) One element may be converted into another.	(ii) No new element can be produced.
(iii) Often accompanied by release or absorption of enormous amount of energy.	(iii) Accormpanied by release or absorption of relatively small amount of energy.
(iv) Rate of reaction is unaffected by external factors such as concentration, temperature, pressure and catalyst.	(iv) Rate of reaction is influenced by external factor.

Types of Nuclear reactions-

A. On the basis of mechainism

(i) Projectile capture reaction : The bombarding particle is absorbed with or without the emission of γ radiations
Example:

(ii) Particle-particle reactions : Majority of nuclear reactions come under this category

B. On the basis of bombarding particle

Nuclear Fission : The process of artificial transmutation in which heavy nucleus is broken down into two lighter nuclei of nearly comparable masses with release of large amount of energy is termed as nuclear fission.
(i) The first nuclear fission to be discovered was that of \({ }_{92}^{225} \mathrm{U}\).
(ii) Over 200 different isotopes of 35 different elements have been found among the fission products of \({ }_{92}^{225} \mathrm{U}\). Most of them are radioactive.
(iii) During fission, there is always lose of mass which is converted into energy according to Einstein equation.
E = Δ mc²(Δ m = mass defect)

(iv) It has been found that at the moment, the energy available from 1 kg of uranium is equivalent to that available from 20,000 kg of coal

Application of Nuclear fission –

(i) Nuclear reactor: A nuclear fission reactor is a device that permits a controlled chain nuclear fission, control rods made of elements such as boron and cadmium, absorb additional neutrons and can therefore, show the chain reaction.
(ii) Atom bomb : It is based on uncontrolled chain reaction. In the atom bomb fissionable material ( ²³⁵U or ²³⁹Pu) is taken in parts in such a way that each is in sub-critical stage. At the time of explosion these pieces one driven together rapidly by using explosives like TNT lying behind each piece of fissonable material make one large piece of fissonable material. At this instant, the overcritical stage is achieved and a fast chain reaction is set up. This result is a violent explosion with the release of tremendous amount of energy.

Nuclear fusion : A nuclear reaction in which two lighter nuclei are fused together to form a havier nuclei is called nuclear fusion.
The process of fusion can take place at extremely high temperature only (>10⁶ K). Such reactions are known as thermo-nuclear reactions.

Application of Nuclearfusion :
(i) Energy of sun : Every second, the sun loses 4.3 × 10⁹ kg (4,20,000 tons) of mass by the fusion reactions. This mass is converted to energy.
(ii) Hydrogen bomb : Hydrogen bomb is based on the fusion of hydrogen nuclei into heavier ones by the thermonuclear reactions with release of enormous energy. In hydrogen bomb, a mixture of deuterium oxide (D₂O) and tritium oxide (T₂O) is enclosed in a space surrounding an atomic bomb. The temperature produced by the explosion of atomic bomb initiates the fusion reaction between \({ }_1^3 \mathrm{H}\) Hand \({ }_1^2 \mathrm{H}\) Hreleasing huge amount of energy.

Difference between Nuclear Fission and Nuclear Fusion :

Nuclear fission	Nuclear fusion
(i) A bigger nucleus splits into smaller nuclei.	(i) Lighter nuclei fuse together to form the heavier nucleus.
(ii) It does not require high temperature.	(ii) Extremely high temperature is required for fusion to take place.
(iii) A chain reaction sets in.	(iii) It is not a chain reaction.
(iv) It can be controlled and energy released can be used for peaceful purposes.	(iv) It cannot be controlled and energy released cannot be used properly.

Application of Redioactivity