CBSE - Animal Kingdom

For the classification of living organisms, common fundamental characteristics are considered.

If we consider specific characteristics, then each organism will be placed in a separate group and the entire objective of classification would not be achieved.

Classification of animals is also important in comparing different organisms and judging their individual evolutionary significance. If only a single characteristic is considered, then this objective would not be achieved.

There is a certain common fundamental feature that helps in classification of living organisms. The features that can be used in classification are as follows.

On the basis of above features, we can easily classify a specimen into its respective category.

Coelom is a fluid filled space between the body wall and digestive tract.

The presence or absence of body cavity or coelom plays a very important role in the classification of animals.

Animals that possess a fluid filled cavity between body wall and digestive tract are known as coelomates. Annelids, mollusks, arthropods, echinodermates, and chordates are examples of coelomates.

On the other hand, the animals in which the body cavity is not lined by mesoderm are known as pseudocoelomates. In such animals, mesoderm is scattered in between ectoderm and endoderm. Aschelminthes is an example of pseudocoelomates.

In certain animals, the body cavity is absent. They are known as acoelomates. An example of acoelomates is platyhelminthes.

Intracellular digestion	Extracellular digestion
The digestion of food occurs within the cell.	The digestion occurs in the cavity of alimentary canal.
Digestive enzymes are secreted by the surrounding cytoplasm into the food vacuole	Digestive enzymes are secreted by special cells into the cavity of alimentary canal.
Digestive products are diffused into the cytoplasm.	Digestive products diffuse across the intestinal wall into various parts of the body.
It is a less efficient method.	It is a more efficient method of digestion.
It occurs in unicellular organisms.	It occurs in multicellular organisms.

Direct development	Indirect development
It is a type of development in which an embryo develops into a mature individual without involving a larval stage.	It is a type of development that involvesa sexually- immature larval stage, having different food requirements than adults.
Metamorphosis is absent.	Metamorphosis involving development of larva to a sexually- mature adult is present.
It occurs in fishes, reptiles, birds, and mammals.	It occurs in most of the invertebrates and amphibians.

Taenia (Tapeworm) and Fasciola (liver fluke) are examples of parasitic platyhelminthes.

Peculiar features in parasitic platyhelminthes are as follows.

1. They have dorsiventrally flattened body and bear hooks and suckers to get attached inside the body of the host.

2. Their body is covered with thick tegument, which protects them from the action of digestive juices of the host.

3. The tegument also helps in absorbing nutrients from the host’s body.

The phylum, Arthropoda, consists of more than two-thirds of the animal species on earth. The reasons for the success of arthropods are as follows.

1. Jointed legs that allow more mobility on land

2. Hard exoskeleton made of chitin that protects the body

3. The hard exoskeleton also reduces water loss from the body of arthropods making them more adapted to terrestrial conditions.

Water vascular system is a characteristic feature of the phylum, Echinodermata. It consists of an array of radiating channels, tube feet, and madreporite. The water vascular system helps in locomotion, food capturing, and respiration.

The characteristic features of the phylum, Chordata, include the presence of a notochord and paired pharyngeal gill slits. In sub-phylum Vertebrata, the notochord present in embryos gets replaced by a cartilaginous or bony vertebral column in adults. Thus, it can be said that all vertebrates are chordates but all chordates are not vertebrates.

Gas bladder or air bladder is a gas filled sac present in fishes. It helps in maintaining buoyancy. Thus, it helps fishes to ascend or descend and stay in the water current.

Birds have undergone many structural adaptations to suit their aerial life. Some of these adaptations are as follows.

(i) Streamlined body for rapid and smooth movement

(ii) Covering of feathers for insulation

(iii) Forelimbs modified into wings and hind limbs used for walking, perching, and swimming

(iv) Presence of pneumatic bones to reduce weight

(v) Presence of additional air sacs to supplement respiration

The numbers of eggs produced by an oviparous mother will be more than the young ones produced by a viviparous mother. This is because in oviparous animals, the development of young ones takes place outside the mother’s body. Their eggs are more prone to environmental conditions and predators. Therefore, to overcome the loss, more eggs are produced by mothers so that even under harsh environmental conditions, some eggs might be able to survive and produce young ones. On the other hand, in viviparous organisms, the development of young ones takes place in safe conditions inside the body of the mother. They are less exposed to environmental conditions and predators. Therefore, there are more chances of their survival and hence, less number of young ones is produced compared to the number of eggs.

The body segmentation first appeared in the phylum, Annelida (annulus meaning little ring).

(a) Operculum	(i) Ctenophora
(b) Parapodia	(ii) Mollusca
(c) Scales	(iii) Porifera
(d) Comb plates	(iv) Reptilia
(e) Radula	(v) Annelida
(f) Hairs	(vi) Cyclostomata and Chondrichthyes
(g) Choanocytes	(vii) Mammalia
(h) Gill slits	(viii) Osteichthyes

Answer:

S. No.	Name of organism	Phylum
1	Taenia solium	Platyhelminthes
2	Fasciola hepatica	Platyhelminthes
3	Ascaris lumbricoides	Aschelminthes
4	Wuchereria bancrofti	Aschelminthes
5	Ancyclostoma	Aschelminthes

(a)  In open circulatory system, blood flows in spaces called sinuses and cells and  tissues are directly  bathed in blood. In closed circulatory system, blood flows through a network of vessels. Arthropods and molluscs have open circulatory system, while annelids and vertebrates have closed circulatory system. 
(b) Oviparous animals lay eggs and young ones hatch from them after some time, e.g. reptiles, birds and some mammals. Viviparous animals give birth to young ones, e.g. scoliodon and most of the mammals.
(c) When the young ones are different from adult animals; this case is called indirect development, e.g. frog, cockroach, silkworm, etc. When the young ones resemble the adult animal; this case is called direct development, e.g. birds, mammals, reptiles, etc. 

Radial Symmetry: Coelenterates, Ctenophores and Echinoderms

Bilateral Symmetry: Annelids and Arthropods

There has been an increase in the n u m b e r  of chambers in heart during evolution of vertebrates. Give the names of the class of vertebrates having two, three or four chambered heart.

Phylum/Class	Excretory Organ	Circulatory Organ	Respiratory Organ
Arthropoda	Malpighian tubules	Open	Lungs/Gills/Tracheal System
Annelids	Nephridia	Closed	Skin/Parapodia
Mollusca	Metanephridia	Open	Gills
Amphibian	Kidneys	Closed	Lung

Column A	Column B
(a) Amphibia	(i) Air bladder
(b) Mammals	(ii) Cartilaginous notochord
(c) Chondrichthye	(iii) Mammary glands
(d) Ostichthyes	(iv) Pneumatic bones
(e) Cyclostomata	(v) Dual habitat
(f) Aves	(vi) Sucking and circular mouth without jaws.

Ans. (a) → (v), (b) → (iii), (c) → (ii), (d) → (i), (e) → (vi), (f) → (iv)

Endoparasites live in nutrient rich environment so most of their adaptations help them in maximizing absorption. In tape worm and round worm; there is an absorbent layer called tegument outside the body. This layer has villi-like structure which helps in better absorption of food. The endoparasites living in small intestine or large intestine get predigested food from their hosts so many of them may not have gut.
However, some of them have both gut and anus. 
Tapeworms also have suckers in mouth to absorb nutrients.

Endoparasites also show mechanisms to get transferred from one host to another. Sometimes, a part of their life cycle is spent in an intermediary host; such as in malarial parasite.
 

Animal	Characteristics
(a) Pila	(i) Jointed appendages
(b) Cockroach	(ii) Perching
(c) Asterias	(iii) Water vascular system
(d) Torpedo	(iv) Electric organ
(e) Parrot	(v) Presence of shell
(f) Dog fish	vi) Placoid scales

Ans. (a) → (v), (b) → (i), (c) → (iii), (d) → (iv), (e) → (ii), (f) → (vi)
 

(a) In open circulatory system, blood flows in spaces called sinuses and cells and tissues are directly bathed in blood. In closed circulatory system, blood flows through a network of vessels. Arthropods and molluscs have open circulatory system, while annelids and vertebrates have closed circulatory system. 
(b) In oviparity; animals lay eggs and young ones hatch from them after some time, e.g. reptiles, birds and some mammals. In viviparity; animals give birth to young ones, e.g. scoliodon and most of the mammals.
(c) When the young ones are different from adult animals; this case is called indirect development, e.g. frog, cockroach, silkworm, etc. When the young ones resemble the adult animal; this case is called direct development e.g. birds, mammals, reptiles etc.  

(d) When body cavity is absent, the animal is called acoelomate, e.g. platyhelminthes. In some animals; mesoderm is present as scattered pouches between ectoderm and endoderm. Such animals are called pseudocoelomate, e.g. aschelminthes. 
(e) The notochord is a flexible rod-shaped body found in embryos of all chordates. It is composed of cells derived from the mesoderm and defines the primitive axis of the embryo. The dorsal nerve cord is a hollow cord dorsal to the notochord. It is formed from a part of the ectoderm that rolls, forming the hollow tube. The notochord is replaced by vertebral column in higher vertebrates. The nerve cord develops into the central nervous system. 
(f) Polyp is a sessile and cylindrical form whereas medusa is umbrella-shaped and free-living. Polyps produces medusae asexually and medusae form the polyps sexually (e.g. Obelia). Examples of polyps are Hydra and Adamasia whereas of medusa is Aurelia.  

(a) Chondrichthyes have cartilaginous endoskeleton and hence they are also called cartilaginous fish. Their skin is covered with placoid scales. Air bladder is absent in them.
Examples: Scoliodon, Pristis etc. Osteichthyes have bony endoskeleton and hence they are also called bony fishes. Their skin is covered with cycloid scales. Air bladder is present in them. Example; Rohu, Catla, etc.

(b) In Urochordata, notochord is present only in the larval tail in larval stage. In Cephalochordata, notochord extends from head to tail region and is present throughout their life. Ascidia and Salpa are examples of urochordate.
Branchiostoma is an example of cephalochordates. Both of these are referred to as protochordates. These are exclusively marine animals.
 

(a) Both of them are worm blooded animals and they have four-chambered heart.
(b) Both of them can live on land as well as in water. Both of them breathe through lungs.
(c) Their body is covered with a hard shell. Both are oviparous animals.
 

(a) Ichtyophis
(b) Frog
(c) Parrot
(d) Python
(e) Sycon
(f) Obelia
 

(a) Chimpanzee
(b) Torpedo
(c) Electric ray
(d) Air bladder
(e) Obelia
(f) Platypus 

Animal	Excretory Organ/Unit
(a) Balanoglossus	(i) Metanephridia
(b) Leech	(ii) Nephridia
(c) Locust	(iii) Flame cells
(d) Liver fluke	(iv) Absent
(e) Sea urchin	(v) Malpighian tubule
(f) Pila	(vi) Proboscis gland

Ans. (a) → (vi), (b) → (ii), (c) → (v), (d) → (iii), (e) → (iv), (f) → (i)
 

Echinodermata.

Pneumatic bones are hollow and hence are light-weight. This helps in weight reduction.

Air sacs are continuous with lungs so that extra air can be filled in air sacs. 

This provides buoyancy. Thus, pneumatic bones and air sacs are flight adaptations in birds.

Cnidarians exhibit two body forms, i.e. polyp and medusa. The sessile forms are called polyps, while the free-swimming forms are called medusa. Some of the cnidarians exhibit alternation of generations in which one generation in polyp form is followed by the next generation in medusa form. This phenomenon is called metagenesis.

Following are the role of feathers in birds:

(a) They create airfoil shape for wings. This provides lift during flight.

(b) They help in maintaining body temperature.

(c) Play important role in mating.

Cyclostomata: These are also called jawless fish, i.e. jaws are absent in these animals.

Placoid scales are found in cartilaginous fish, e.g. scoliodon. Cycoid scales are found in bony fish, e.g. rohu.

Following are the two modifications in reptiles required for terrestrial mode of life:

(a) Dry and cornified skin and epidermal scales.

(b) Internal fertilization

Arthropods have chitinous exoskeleton, e.g. cockroach. Molluscs have calcareous shell,

e.g. Pila.

Radula is a file-like rasping organ found in molluscs. It helps in scraping and scratching the food. It also helps in creating depressions in rocks. Such depressions are used by these animals as home.

Pleurobrachia and Ctenoplana are animals which exhibit bioluminescence. These animals belong to the phylum Ctenophora.

(a) Frog

(b) Pigeon

(c) Snake

(d) Ascaris

There are two embryonic layers in diploblastic animals, viz. ectoderm and endoderm.

There are three embryonic layers in triploblastic animals, viz. ectoderm, mesoderm and endoderm.

(a) Ascaris

(b) Trygon

(c) Ichthyophis

(d) Platypus

(a) Blood-filled cavity in arthropods _____.

(b) Free-floating form of cnidaria _____.

(c) Stinging organ of jelly fishes _____.

(d) Lateral appendages in aquatic annelids _____.

Ans. (a) Haemocoel

(b) Medusa

(c) Nematocytes

(d) Parapodia

Animals	Locomotory Organ
(a) Octopus	(i) Limbs
(b) Crocodile	(ii) Comb        plates
(c) Catla	(iii) Tentacles
(d) Ctenoplana	(iv) Fins

Ans.    (a) -> (iii),    (b)-> (i),    (c)-> (iv),    (d)-> (ii)

Ans. (b) Metamerism
Explanation: Segments in such animals are called metameres and this phenomenon is called metamerism.
 

Ans. (b) Interstitial cells
Explanation: Other cells in the options cannot differentiate. But interstitial cells in testes and ovary can differentiate.
 

(b) Crocodiles, Birds, Mammals
Explanation: Amphibians have two-chambered heart, while most of the reptiles have three-chambered heart. Crocodiles, birds and mammals have four-chambered heart.
 

(b) Chameleon and Turtle

Explanation: Glandular skin is present in frog, snake and crocodile. Mammals too have glandular skin. Hence, option ‘b’ is the correct option.
 

Ans. (d) Warm blooded
Explanation: Pneumatic bones and viviparity is present in birds but not in mammals. Pigmented skin is present only in mammals. Hence, ‘d’ is the correct option. 

Ans. (c) Monkey, Chimpanzee, Man

Explanation: In option ‘c’ all organisms belong to mammalia. Option ‘a’ has dogfish and starfish as odd ments out. Option ‘b’ has animals from three different taxa. Option ‘d’ also has animals from three different taxa. 

Ans. (c) Fasciola is a pseudocoelomate animal 

Explanation: Fasciola is acoelomate animal. 

Ans. (a) In cockroaches and prawns excretion of waste material occurs through malpighian tubules.

Ans. (a) Platypus
Explanation: Platypus and echidna are oviparous mammals.

Ans. (c) Python

Ans. (c) (i)-(D), (ii)-(A), (iii)-(B), and (iv)-(C)

Ans. (b) Pseudocoelomate

Ans. (c) (A)-(i), (B)-(iii), (C)-(v), (D)-(iv), (E)-(ii)

Chordates	Non-chordates
(i) Notochord is present in at least one stage of the life cycle.	(i) Notochord is absent.
(ii) Pharyngeal gill slits are present	(ii) Pharyngeal gill slits absent.
(iii)  Post anal tail is present.	(iii) Post anal tail is absent.
(iv) Heart is ventrally located.	(iv) Heart (if present) is dorsally located.
(v) Cent ra l  nervous system is dorsally located and is hollow.	(v) Central nervous  system is ventrally located and is solid.

(i) Coelomate: There are two germinal layers in coelomates, viz. ectoderm, mesoderm and endoderm. The mesoderm lines the body cavity ad thus body cavity  is
present.
(ii) Acoelomate: There are two germinal layers in acoelomates, viz. ectoderm and endoderm. Body cavity is not present in coelomate.
(iii) Pseudocoelomate: There are three germinal layers in pseudocoelomate, viz. ectoderm, mesoderm and endoderm. But mesoderm is present as scattered
pouches and hence true coelom is absent. 

(i)  Amphibia
(a) Habitat: They live in freshwater and marine water. They can also live on land.
(b) External Features: Body is divided into head and trunk. Tail may be present in some. Skin is moist and has no scales. Eyes have eyelids. Tympanum represents
the ear.
(ii) Reptilia
(a) Habitat: They are primarily terrestrial animals. However, some are found in  aquatic habitat as well. But they cannot breathe under water. Limbs are in two pairs. 
(b) External Features: Skin is dry and covered with cornified scales. Tympanum represents the ear. Limbs (if present) are in two pairs. 

It is true that mammals are most adapted among vertebrates. Following are some of the adaptions shown by mammals:
(i) Mammals can be found in almost all types of habitat, e.g. in mountains, deserts, grasslands, plains and even in aquatic habitat.
(ii) Mammals have two pairs of limbs which help in running, jumping, walking, flying, climbing and burrowing.
(iii) Mammalian skin is equipped with sweat glands which help in osmoregulation and thermoregulation.
(iv) Hairs on skin provide insulation.
(v) External ears help in catching sound waves in efficient way.
(vi) Four-chambered heart facilitates double circulation which is more efficient than single circulation.
(vii) They are warm blooded animals which means they can control their body temperature.
(viii) Sexual dimorphism is well developed which is an important tool for survival. 
(ix) Most of the mammals are viviparous. This helps in longer life span of mammals.  

For the classification of living organisms, common fundamental characteristics are considered.

If we consider specific characteristics, then each organism will be placed in a separate group and the entire objective of classification would not be achieved.

Classification of animals is also important in comparing different organisms and judging their individual evolutionary significance. If only a single characteristic is considered, then this objective would not be achieved.

There is a certain common fundamental feature that helps in classification of living organisms. The features that can be used in classification are as follows.

On the basis of above features, we can easily classify a specimen into its respective category.

Coelom is a fluid filled space between the body wall and digestive tract.

The presence or absence of body cavity or coelom plays a very important role in the classification of animals.

Animals that possess a fluid filled cavity between body wall and digestive tract are known as coelomates. Annelids, mollusks, arthropods, echinodermates, and chordates are examples of coelomates.

On the other hand, the animals in which the body cavity is not lined by mesoderm are known as pseudocoelomates. In such animals, mesoderm is scattered in between ectoderm and endoderm. Aschelminthes is an example of pseudocoelomates.

In certain animals, the body cavity is absent. They are known as acoelomates. An example of acoelomates is platyhelminthes.

Intracellular digestion	Extracellular digestion
The digestion of food occurs within the cell.	The digestion occurs in the cavity of alimentary canal.
Digestive enzymes are secreted by the surrounding cytoplasm into the food vacuole	Digestive enzymes are secreted by special cells into the cavity of alimentary canal.
Digestive products are diffused into the cytoplasm.	Digestive products diffuse across the intestinal wall into various parts of the body.
It is a less efficient method.	It is a more efficient method of digestion.
It occurs in unicellular organisms.	It occurs in multicellular organisms.

Direct development	Indirect development
It is a type of development in which an embryo develops into a mature individual without involving a larval stage.	It is a type of development that involvesa sexually- immature larval stage, having different food requirements than adults.
Metamorphosis is absent.	Metamorphosis involving development of larva to a sexually- mature adult is present.
It occurs in fishes, reptiles, birds, and mammals.	It occurs in most of the invertebrates and amphibians.

Taenia (Tapeworm) and Fasciola (liver fluke) are examples of parasitic platyhelminthes.

Peculiar features in parasitic platyhelminthes are as follows.

1. They have dorsiventrally flattened body and bear hooks and suckers to get attached inside the body of the host.

2. Their body is covered with thick tegument, which protects them from the action of digestive juices of the host.

3. The tegument also helps in absorbing nutrients from the host’s body.

The phylum, Arthropoda, consists of more than two-thirds of the animal species on earth. The reasons for the success of arthropods are as follows.

1. Jointed legs that allow more mobility on land

2. Hard exoskeleton made of chitin that protects the body

3. The hard exoskeleton also reduces water loss from the body of arthropods making them more adapted to terrestrial conditions.

Water vascular system is a characteristic feature of the phylum, Echinodermata. It consists of an array of radiating channels, tube feet, and madreporite. The water vascular system helps in locomotion, food capturing, and respiration.

The characteristic features of the phylum, Chordata, include the presence of a notochord and paired pharyngeal gill slits. In sub-phylum Vertebrata, the notochord present in embryos gets replaced by a cartilaginous or bony vertebral column in adults. Thus, it can be said that all vertebrates are chordates but all chordates are not vertebrates.

Gas bladder or air bladder is a gas filled sac present in fishes. It helps in maintaining buoyancy. Thus, it helps fishes to ascend or descend and stay in the water current.

Birds have undergone many structural adaptations to suit their aerial life. Some of these adaptations are as follows.

(i) Streamlined body for rapid and smooth movement

(ii) Covering of feathers for insulation

(iii) Forelimbs modified into wings and hind limbs used for walking, perching, and swimming

(iv) Presence of pneumatic bones to reduce weight

(v) Presence of additional air sacs to supplement respiration

The numbers of eggs produced by an oviparous mother will be more than the young ones produced by a viviparous mother. This is because in oviparous animals, the development of young ones takes place outside the mother’s body. Their eggs are more prone to environmental conditions and predators. Therefore, to overcome the loss, more eggs are produced by mothers so that even under harsh environmental conditions, some eggs might be able to survive and produce young ones. On the other hand, in viviparous organisms, the development of young ones takes place in safe conditions inside the body of the mother. They are less exposed to environmental conditions and predators. Therefore, there are more chances of their survival and hence, less number of young ones is produced compared to the number of eggs.

The body segmentation first appeared in the phylum, Annelida (annulus meaning little ring).

(a) Operculum	(i) Ctenophora
(b) Parapodia	(ii) Mollusca
(c) Scales	(iii) Porifera
(d) Comb plates	(iv) Reptilia
(e) Radula	(v) Annelida
(f) Hairs	(vi) Cyclostomata and Chondrichthyes
(g) Choanocytes	(vii) Mammalia
(h) Gill slits	(viii) Osteichthyes

Answer:

S. No.	Name of organism	Phylum
1	Taenia solium	Platyhelminthes
2	Fasciola hepatica	Platyhelminthes
3	Ascaris lumbricoides	Aschelminthes
4	Wuchereria bancrofti	Aschelminthes
5	Ancyclostoma	Aschelminthes

(a)  In open circulatory system, blood flows in spaces called sinuses and cells and  tissues are directly  bathed in blood. In closed circulatory system, blood flows through a network of vessels. Arthropods and molluscs have open circulatory system, while annelids and vertebrates have closed circulatory system. 
(b) Oviparous animals lay eggs and young ones hatch from them after some time, e.g. reptiles, birds and some mammals. Viviparous animals give birth to young ones, e.g. scoliodon and most of the mammals.
(c) When the young ones are different from adult animals; this case is called indirect development, e.g. frog, cockroach, silkworm, etc. When the young ones resemble the adult animal; this case is called direct development, e.g. birds, mammals, reptiles, etc. 

Radial Symmetry: Coelenterates, Ctenophores and Echinoderms

Bilateral Symmetry: Annelids and Arthropods

There has been an increase in the n u m b e r  of chambers in heart during evolution of vertebrates. Give the names of the class of vertebrates having two, three or four chambered heart.

Phylum/Class	Excretory Organ	Circulatory Organ	Respiratory Organ
Arthropoda	Malpighian tubules	Open	Lungs/Gills/Tracheal System
Annelids	Nephridia	Closed	Skin/Parapodia
Mollusca	Metanephridia	Open	Gills
Amphibian	Kidneys	Closed	Lung

Column A	Column B
(a) Amphibia	(i) Air bladder
(b) Mammals	(ii) Cartilaginous notochord
(c) Chondrichthye	(iii) Mammary glands
(d) Ostichthyes	(iv) Pneumatic bones
(e) Cyclostomata	(v) Dual habitat
(f) Aves	(vi) Sucking and circular mouth without jaws.

Ans. (a) → (v), (b) → (iii), (c) → (ii), (d) → (i), (e) → (vi), (f) → (iv)

Endoparasites live in nutrient rich environment so most of their adaptations help them in maximizing absorption. In tape worm and round worm; there is an absorbent layer called tegument outside the body. This layer has villi-like structure which helps in better absorption of food. The endoparasites living in small intestine or large intestine get predigested food from their hosts so many of them may not have gut.
However, some of them have both gut and anus. 
Tapeworms also have suckers in mouth to absorb nutrients.

Endoparasites also show mechanisms to get transferred from one host to another. Sometimes, a part of their life cycle is spent in an intermediary host; such as in malarial parasite.
 

Animal	Characteristics
(a) Pila	(i) Jointed appendages
(b) Cockroach	(ii) Perching
(c) Asterias	(iii) Water vascular system
(d) Torpedo	(iv) Electric organ
(e) Parrot	(v) Presence of shell
(f) Dog fish	vi) Placoid scales

Ans. (a) → (v), (b) → (i), (c) → (iii), (d) → (iv), (e) → (ii), (f) → (vi)
 

(a) In open circulatory system, blood flows in spaces called sinuses and cells and tissues are directly bathed in blood. In closed circulatory system, blood flows through a network of vessels. Arthropods and molluscs have open circulatory system, while annelids and vertebrates have closed circulatory system. 
(b) In oviparity; animals lay eggs and young ones hatch from them after some time, e.g. reptiles, birds and some mammals. In viviparity; animals give birth to young ones, e.g. scoliodon and most of the mammals.
(c) When the young ones are different from adult animals; this case is called indirect development, e.g. frog, cockroach, silkworm, etc. When the young ones resemble the adult animal; this case is called direct development e.g. birds, mammals, reptiles etc.  

(d) When body cavity is absent, the animal is called acoelomate, e.g. platyhelminthes. In some animals; mesoderm is present as scattered pouches between ectoderm and endoderm. Such animals are called pseudocoelomate, e.g. aschelminthes. 
(e) The notochord is a flexible rod-shaped body found in embryos of all chordates. It is composed of cells derived from the mesoderm and defines the primitive axis of the embryo. The dorsal nerve cord is a hollow cord dorsal to the notochord. It is formed from a part of the ectoderm that rolls, forming the hollow tube. The notochord is replaced by vertebral column in higher vertebrates. The nerve cord develops into the central nervous system. 
(f) Polyp is a sessile and cylindrical form whereas medusa is umbrella-shaped and free-living. Polyps produces medusae asexually and medusae form the polyps sexually (e.g. Obelia). Examples of polyps are Hydra and Adamasia whereas of medusa is Aurelia.  

(a) Chondrichthyes have cartilaginous endoskeleton and hence they are also called cartilaginous fish. Their skin is covered with placoid scales. Air bladder is absent in them.
Examples: Scoliodon, Pristis etc. Osteichthyes have bony endoskeleton and hence they are also called bony fishes. Their skin is covered with cycloid scales. Air bladder is present in them. Example; Rohu, Catla, etc.

(b) In Urochordata, notochord is present only in the larval tail in larval stage. In Cephalochordata, notochord extends from head to tail region and is present throughout their life. Ascidia and Salpa are examples of urochordate.
Branchiostoma is an example of cephalochordates. Both of these are referred to as protochordates. These are exclusively marine animals.
 

(a) Both of them are worm blooded animals and they have four-chambered heart.
(b) Both of them can live on land as well as in water. Both of them breathe through lungs.
(c) Their body is covered with a hard shell. Both are oviparous animals.
 

(a) Ichtyophis
(b) Frog
(c) Parrot
(d) Python
(e) Sycon
(f) Obelia
 

(a) Chimpanzee
(b) Torpedo
(c) Electric ray
(d) Air bladder
(e) Obelia
(f) Platypus 

Animal	Excretory Organ/Unit
(a) Balanoglossus	(i) Metanephridia
(b) Leech	(ii) Nephridia
(c) Locust	(iii) Flame cells
(d) Liver fluke	(iv) Absent
(e) Sea urchin	(v) Malpighian tubule
(f) Pila	(vi) Proboscis gland

Ans. (a) → (vi), (b) → (ii), (c) → (v), (d) → (iii), (e) → (iv), (f) → (i)
 

Echinodermata.

Pneumatic bones are hollow and hence are light-weight. This helps in weight reduction.

Air sacs are continuous with lungs so that extra air can be filled in air sacs. 

This provides buoyancy. Thus, pneumatic bones and air sacs are flight adaptations in birds.

Cnidarians exhibit two body forms, i.e. polyp and medusa. The sessile forms are called polyps, while the free-swimming forms are called medusa. Some of the cnidarians exhibit alternation of generations in which one generation in polyp form is followed by the next generation in medusa form. This phenomenon is called metagenesis.

Following are the role of feathers in birds:

(a) They create airfoil shape for wings. This provides lift during flight.

(b) They help in maintaining body temperature.

(c) Play important role in mating.

Cyclostomata: These are also called jawless fish, i.e. jaws are absent in these animals.

Placoid scales are found in cartilaginous fish, e.g. scoliodon. Cycoid scales are found in bony fish, e.g. rohu.

Following are the two modifications in reptiles required for terrestrial mode of life:

(a) Dry and cornified skin and epidermal scales.

(b) Internal fertilization

Arthropods have chitinous exoskeleton, e.g. cockroach. Molluscs have calcareous shell,

e.g. Pila.

Radula is a file-like rasping organ found in molluscs. It helps in scraping and scratching the food. It also helps in creating depressions in rocks. Such depressions are used by these animals as home.

Pleurobrachia and Ctenoplana are animals which exhibit bioluminescence. These animals belong to the phylum Ctenophora.

(a) Frog

(b) Pigeon

(c) Snake

(d) Ascaris

There are two embryonic layers in diploblastic animals, viz. ectoderm and endoderm.

There are three embryonic layers in triploblastic animals, viz. ectoderm, mesoderm and endoderm.

(a) Ascaris

(b) Trygon

(c) Ichthyophis

(d) Platypus

(a) Blood-filled cavity in arthropods _____.

(b) Free-floating form of cnidaria _____.

(c) Stinging organ of jelly fishes _____.

(d) Lateral appendages in aquatic annelids _____.

Ans. (a) Haemocoel

(b) Medusa

(c) Nematocytes

(d) Parapodia

Animals	Locomotory Organ
(a) Octopus	(i) Limbs
(b) Crocodile	(ii) Comb        plates
(c) Catla	(iii) Tentacles
(d) Ctenoplana	(iv) Fins

Ans.    (a) -> (iii),    (b)-> (i),    (c)-> (iv),    (d)-> (ii)

Ans. (b) Metamerism
Explanation: Segments in such animals are called metameres and this phenomenon is called metamerism.
 

Ans. (b) Interstitial cells
Explanation: Other cells in the options cannot differentiate. But interstitial cells in testes and ovary can differentiate.
 

(b) Crocodiles, Birds, Mammals
Explanation: Amphibians have two-chambered heart, while most of the reptiles have three-chambered heart. Crocodiles, birds and mammals have four-chambered heart.
 

(b) Chameleon and Turtle

Explanation: Glandular skin is present in frog, snake and crocodile. Mammals too have glandular skin. Hence, option ‘b’ is the correct option.
 

Ans. (d) Warm blooded
Explanation: Pneumatic bones and viviparity is present in birds but not in mammals. Pigmented skin is present only in mammals. Hence, ‘d’ is the correct option. 

Ans. (c) Monkey, Chimpanzee, Man

Explanation: In option ‘c’ all organisms belong to mammalia. Option ‘a’ has dogfish and starfish as odd ments out. Option ‘b’ has animals from three different taxa. Option ‘d’ also has animals from three different taxa. 

Ans. (c) Fasciola is a pseudocoelomate animal 

Explanation: Fasciola is acoelomate animal. 

Ans. (a) In cockroaches and prawns excretion of waste material occurs through malpighian tubules.

Ans. (a) Platypus
Explanation: Platypus and echidna are oviparous mammals.

Ans. (c) Python

Ans. (c) (i)-(D), (ii)-(A), (iii)-(B), and (iv)-(C)

Ans. (b) Pseudocoelomate

Ans. (c) (A)-(i), (B)-(iii), (C)-(v), (D)-(iv), (E)-(ii)

Chordates	Non-chordates
(i) Notochord is present in at least one stage of the life cycle.	(i) Notochord is absent.
(ii) Pharyngeal gill slits are present	(ii) Pharyngeal gill slits absent.
(iii)  Post anal tail is present.	(iii) Post anal tail is absent.
(iv) Heart is ventrally located.	(iv) Heart (if present) is dorsally located.
(v) Cent ra l  nervous system is dorsally located and is hollow.	(v) Central nervous  system is ventrally located and is solid.

(i) Coelomate: There are two germinal layers in coelomates, viz. ectoderm, mesoderm and endoderm. The mesoderm lines the body cavity ad thus body cavity  is
present.
(ii) Acoelomate: There are two germinal layers in acoelomates, viz. ectoderm and endoderm. Body cavity is not present in coelomate.
(iii) Pseudocoelomate: There are three germinal layers in pseudocoelomate, viz. ectoderm, mesoderm and endoderm. But mesoderm is present as scattered
pouches and hence true coelom is absent. 

(i)  Amphibia
(a) Habitat: They live in freshwater and marine water. They can also live on land.
(b) External Features: Body is divided into head and trunk. Tail may be present in some. Skin is moist and has no scales. Eyes have eyelids. Tympanum represents
the ear.
(ii) Reptilia
(a) Habitat: They are primarily terrestrial animals. However, some are found in  aquatic habitat as well. But they cannot breathe under water. Limbs are in two pairs. 
(b) External Features: Skin is dry and covered with cornified scales. Tympanum represents the ear. Limbs (if present) are in two pairs. 

It is true that mammals are most adapted among vertebrates. Following are some of the adaptions shown by mammals:
(i) Mammals can be found in almost all types of habitat, e.g. in mountains, deserts, grasslands, plains and even in aquatic habitat.
(ii) Mammals have two pairs of limbs which help in running, jumping, walking, flying, climbing and burrowing.
(iii) Mammalian skin is equipped with sweat glands which help in osmoregulation and thermoregulation.
(iv) Hairs on skin provide insulation.
(v) External ears help in catching sound waves in efficient way.
(vi) Four-chambered heart facilitates double circulation which is more efficient than single circulation.
(vii) They are warm blooded animals which means they can control their body temperature.
(viii) Sexual dimorphism is well developed which is an important tool for survival. 
(ix) Most of the mammals are viviparous. This helps in longer life span of mammals.  

For the classification of living organisms, common fundamental characteristics are considered.

If we consider specific characteristics, then each organism will be placed in a separate group and the entire objective of classification would not be achieved.

Classification of animals is also important in comparing different organisms and judging their individual evolutionary significance. If only a single characteristic is considered, then this objective would not be achieved.

There is a certain common fundamental feature that helps in classification of living organisms. The features that can be used in classification are as follows.

On the basis of above features, we can easily classify a specimen into its respective category.

Coelom is a fluid filled space between the body wall and digestive tract.

The presence or absence of body cavity or coelom plays a very important role in the classification of animals.

Animals that possess a fluid filled cavity between body wall and digestive tract are known as coelomates. Annelids, mollusks, arthropods, echinodermates, and chordates are examples of coelomates.

On the other hand, the animals in which the body cavity is not lined by mesoderm are known as pseudocoelomates. In such animals, mesoderm is scattered in between ectoderm and endoderm. Aschelminthes is an example of pseudocoelomates.

In certain animals, the body cavity is absent. They are known as acoelomates. An example of acoelomates is platyhelminthes.

Intracellular digestion	Extracellular digestion
The digestion of food occurs within the cell.	The digestion occurs in the cavity of alimentary canal.
Digestive enzymes are secreted by the surrounding cytoplasm into the food vacuole	Digestive enzymes are secreted by special cells into the cavity of alimentary canal.
Digestive products are diffused into the cytoplasm.	Digestive products diffuse across the intestinal wall into various parts of the body.
It is a less efficient method.	It is a more efficient method of digestion.
It occurs in unicellular organisms.	It occurs in multicellular organisms.

Direct development	Indirect development
It is a type of development in which an embryo develops into a mature individual without involving a larval stage.	It is a type of development that involvesa sexually- immature larval stage, having different food requirements than adults.
Metamorphosis is absent.	Metamorphosis involving development of larva to a sexually- mature adult is present.
It occurs in fishes, reptiles, birds, and mammals.	It occurs in most of the invertebrates and amphibians.

Taenia (Tapeworm) and Fasciola (liver fluke) are examples of parasitic platyhelminthes.

Peculiar features in parasitic platyhelminthes are as follows.

1. They have dorsiventrally flattened body and bear hooks and suckers to get attached inside the body of the host.

2. Their body is covered with thick tegument, which protects them from the action of digestive juices of the host.

3. The tegument also helps in absorbing nutrients from the host’s body.

The phylum, Arthropoda, consists of more than two-thirds of the animal species on earth. The reasons for the success of arthropods are as follows.

1. Jointed legs that allow more mobility on land

2. Hard exoskeleton made of chitin that protects the body

3. The hard exoskeleton also reduces water loss from the body of arthropods making them more adapted to terrestrial conditions.

Water vascular system is a characteristic feature of the phylum, Echinodermata. It consists of an array of radiating channels, tube feet, and madreporite. The water vascular system helps in locomotion, food capturing, and respiration.

The characteristic features of the phylum, Chordata, include the presence of a notochord and paired pharyngeal gill slits. In sub-phylum Vertebrata, the notochord present in embryos gets replaced by a cartilaginous or bony vertebral column in adults. Thus, it can be said that all vertebrates are chordates but all chordates are not vertebrates.

Gas bladder or air bladder is a gas filled sac present in fishes. It helps in maintaining buoyancy. Thus, it helps fishes to ascend or descend and stay in the water current.

Birds have undergone many structural adaptations to suit their aerial life. Some of these adaptations are as follows.

(i) Streamlined body for rapid and smooth movement

(ii) Covering of feathers for insulation

(iii) Forelimbs modified into wings and hind limbs used for walking, perching, and swimming

(iv) Presence of pneumatic bones to reduce weight

(v) Presence of additional air sacs to supplement respiration

The numbers of eggs produced by an oviparous mother will be more than the young ones produced by a viviparous mother. This is because in oviparous animals, the development of young ones takes place outside the mother’s body. Their eggs are more prone to environmental conditions and predators. Therefore, to overcome the loss, more eggs are produced by mothers so that even under harsh environmental conditions, some eggs might be able to survive and produce young ones. On the other hand, in viviparous organisms, the development of young ones takes place in safe conditions inside the body of the mother. They are less exposed to environmental conditions and predators. Therefore, there are more chances of their survival and hence, less number of young ones is produced compared to the number of eggs.

The body segmentation first appeared in the phylum, Annelida (annulus meaning little ring).

(a) Operculum	(i) Ctenophora
(b) Parapodia	(ii) Mollusca
(c) Scales	(iii) Porifera
(d) Comb plates	(iv) Reptilia
(e) Radula	(v) Annelida
(f) Hairs	(vi) Cyclostomata and Chondrichthyes
(g) Choanocytes	(vii) Mammalia
(h) Gill slits	(viii) Osteichthyes

Answer:

S. No.	Name of organism	Phylum
1	Taenia solium	Platyhelminthes
2	Fasciola hepatica	Platyhelminthes
3	Ascaris lumbricoides	Aschelminthes
4	Wuchereria bancrofti	Aschelminthes
5	Ancyclostoma	Aschelminthes

(a)  In open circulatory system, blood flows in spaces called sinuses and cells and  tissues are directly  bathed in blood. In closed circulatory system, blood flows through a network of vessels. Arthropods and molluscs have open circulatory system, while annelids and vertebrates have closed circulatory system. 
(b) Oviparous animals lay eggs and young ones hatch from them after some time, e.g. reptiles, birds and some mammals. Viviparous animals give birth to young ones, e.g. scoliodon and most of the mammals.
(c) When the young ones are different from adult animals; this case is called indirect development, e.g. frog, cockroach, silkworm, etc. When the young ones resemble the adult animal; this case is called direct development, e.g. birds, mammals, reptiles, etc. 

Radial Symmetry: Coelenterates, Ctenophores and Echinoderms

Bilateral Symmetry: Annelids and Arthropods

There has been an increase in the n u m b e r  of chambers in heart during evolution of vertebrates. Give the names of the class of vertebrates having two, three or four chambered heart.

Phylum/Class	Excretory Organ	Circulatory Organ	Respiratory Organ
Arthropoda	Malpighian tubules	Open	Lungs/Gills/Tracheal System
Annelids	Nephridia	Closed	Skin/Parapodia
Mollusca	Metanephridia	Open	Gills
Amphibian	Kidneys	Closed	Lung

Column A	Column B
(a) Amphibia	(i) Air bladder
(b) Mammals	(ii) Cartilaginous notochord
(c) Chondrichthye	(iii) Mammary glands
(d) Ostichthyes	(iv) Pneumatic bones
(e) Cyclostomata	(v) Dual habitat
(f) Aves	(vi) Sucking and circular mouth without jaws.

Ans. (a) → (v), (b) → (iii), (c) → (ii), (d) → (i), (e) → (vi), (f) → (iv)

Endoparasites live in nutrient rich environment so most of their adaptations help them in maximizing absorption. In tape worm and round worm; there is an absorbent layer called tegument outside the body. This layer has villi-like structure which helps in better absorption of food. The endoparasites living in small intestine or large intestine get predigested food from their hosts so many of them may not have gut.
However, some of them have both gut and anus. 
Tapeworms also have suckers in mouth to absorb nutrients.

Endoparasites also show mechanisms to get transferred from one host to another. Sometimes, a part of their life cycle is spent in an intermediary host; such as in malarial parasite.
 

Animal	Characteristics
(a) Pila	(i) Jointed appendages
(b) Cockroach	(ii) Perching
(c) Asterias	(iii) Water vascular system
(d) Torpedo	(iv) Electric organ
(e) Parrot	(v) Presence of shell
(f) Dog fish	vi) Placoid scales

Ans. (a) → (v), (b) → (i), (c) → (iii), (d) → (iv), (e) → (ii), (f) → (vi)
 

(a) In open circulatory system, blood flows in spaces called sinuses and cells and tissues are directly bathed in blood. In closed circulatory system, blood flows through a network of vessels. Arthropods and molluscs have open circulatory system, while annelids and vertebrates have closed circulatory system. 
(b) In oviparity; animals lay eggs and young ones hatch from them after some time, e.g. reptiles, birds and some mammals. In viviparity; animals give birth to young ones, e.g. scoliodon and most of the mammals.
(c) When the young ones are different from adult animals; this case is called indirect development, e.g. frog, cockroach, silkworm, etc. When the young ones resemble the adult animal; this case is called direct development e.g. birds, mammals, reptiles etc.  

(d) When body cavity is absent, the animal is called acoelomate, e.g. platyhelminthes. In some animals; mesoderm is present as scattered pouches between ectoderm and endoderm. Such animals are called pseudocoelomate, e.g. aschelminthes. 
(e) The notochord is a flexible rod-shaped body found in embryos of all chordates. It is composed of cells derived from the mesoderm and defines the primitive axis of the embryo. The dorsal nerve cord is a hollow cord dorsal to the notochord. It is formed from a part of the ectoderm that rolls, forming the hollow tube. The notochord is replaced by vertebral column in higher vertebrates. The nerve cord develops into the central nervous system. 
(f) Polyp is a sessile and cylindrical form whereas medusa is umbrella-shaped and free-living. Polyps produces medusae asexually and medusae form the polyps sexually (e.g. Obelia). Examples of polyps are Hydra and Adamasia whereas of medusa is Aurelia.  

(a) Chondrichthyes have cartilaginous endoskeleton and hence they are also called cartilaginous fish. Their skin is covered with placoid scales. Air bladder is absent in them.
Examples: Scoliodon, Pristis etc. Osteichthyes have bony endoskeleton and hence they are also called bony fishes. Their skin is covered with cycloid scales. Air bladder is present in them. Example; Rohu, Catla, etc.

(b) In Urochordata, notochord is present only in the larval tail in larval stage. In Cephalochordata, notochord extends from head to tail region and is present throughout their life. Ascidia and Salpa are examples of urochordate.
Branchiostoma is an example of cephalochordates. Both of these are referred to as protochordates. These are exclusively marine animals.
 

(a) Both of them are worm blooded animals and they have four-chambered heart.
(b) Both of them can live on land as well as in water. Both of them breathe through lungs.
(c) Their body is covered with a hard shell. Both are oviparous animals.
 

(a) Ichtyophis
(b) Frog
(c) Parrot
(d) Python
(e) Sycon
(f) Obelia
 

(a) Chimpanzee
(b) Torpedo
(c) Electric ray
(d) Air bladder
(e) Obelia
(f) Platypus 

Animal	Excretory Organ/Unit
(a) Balanoglossus	(i) Metanephridia
(b) Leech	(ii) Nephridia
(c) Locust	(iii) Flame cells
(d) Liver fluke	(iv) Absent
(e) Sea urchin	(v) Malpighian tubule
(f) Pila	(vi) Proboscis gland

Ans. (a) → (vi), (b) → (ii), (c) → (v), (d) → (iii), (e) → (iv), (f) → (i)
 

Echinodermata.

Pneumatic bones are hollow and hence are light-weight. This helps in weight reduction.

Air sacs are continuous with lungs so that extra air can be filled in air sacs. 

This provides buoyancy. Thus, pneumatic bones and air sacs are flight adaptations in birds.

Cnidarians exhibit two body forms, i.e. polyp and medusa. The sessile forms are called polyps, while the free-swimming forms are called medusa. Some of the cnidarians exhibit alternation of generations in which one generation in polyp form is followed by the next generation in medusa form. This phenomenon is called metagenesis.

Following are the role of feathers in birds:

(a) They create airfoil shape for wings. This provides lift during flight.

(b) They help in maintaining body temperature.

(c) Play important role in mating.

Cyclostomata: These are also called jawless fish, i.e. jaws are absent in these animals.

Placoid scales are found in cartilaginous fish, e.g. scoliodon. Cycoid scales are found in bony fish, e.g. rohu.

Following are the two modifications in reptiles required for terrestrial mode of life:

(a) Dry and cornified skin and epidermal scales.

(b) Internal fertilization

Arthropods have chitinous exoskeleton, e.g. cockroach. Molluscs have calcareous shell,

e.g. Pila.

Radula is a file-like rasping organ found in molluscs. It helps in scraping and scratching the food. It also helps in creating depressions in rocks. Such depressions are used by these animals as home.

Pleurobrachia and Ctenoplana are animals which exhibit bioluminescence. These animals belong to the phylum Ctenophora.

(a) Frog

(b) Pigeon

(c) Snake

(d) Ascaris

There are two embryonic layers in diploblastic animals, viz. ectoderm and endoderm.

There are three embryonic layers in triploblastic animals, viz. ectoderm, mesoderm and endoderm.

(a) Ascaris

(b) Trygon

(c) Ichthyophis

(d) Platypus

(a) Blood-filled cavity in arthropods _____.

(b) Free-floating form of cnidaria _____.

(c) Stinging organ of jelly fishes _____.

(d) Lateral appendages in aquatic annelids _____.

Ans. (a) Haemocoel

(b) Medusa

(c) Nematocytes

(d) Parapodia

Animals	Locomotory Organ
(a) Octopus	(i) Limbs
(b) Crocodile	(ii) Comb        plates
(c) Catla	(iii) Tentacles
(d) Ctenoplana	(iv) Fins

Ans.    (a) -> (iii),    (b)-> (i),    (c)-> (iv),    (d)-> (ii)

Ans. (b) Metamerism
Explanation: Segments in such animals are called metameres and this phenomenon is called metamerism.
 

Ans. (b) Interstitial cells
Explanation: Other cells in the options cannot differentiate. But interstitial cells in testes and ovary can differentiate.
 

(b) Crocodiles, Birds, Mammals
Explanation: Amphibians have two-chambered heart, while most of the reptiles have three-chambered heart. Crocodiles, birds and mammals have four-chambered heart.
 

(b) Chameleon and Turtle

Explanation: Glandular skin is present in frog, snake and crocodile. Mammals too have glandular skin. Hence, option ‘b’ is the correct option.
 

Ans. (d) Warm blooded
Explanation: Pneumatic bones and viviparity is present in birds but not in mammals. Pigmented skin is present only in mammals. Hence, ‘d’ is the correct option. 

Ans. (c) Monkey, Chimpanzee, Man

Explanation: In option ‘c’ all organisms belong to mammalia. Option ‘a’ has dogfish and starfish as odd ments out. Option ‘b’ has animals from three different taxa. Option ‘d’ also has animals from three different taxa. 

Ans. (c) Fasciola is a pseudocoelomate animal 

Explanation: Fasciola is acoelomate animal. 

Ans. (a) In cockroaches and prawns excretion of waste material occurs through malpighian tubules.

Ans. (a) Platypus
Explanation: Platypus and echidna are oviparous mammals.

Ans. (c) Python

Ans. (c) (i)-(D), (ii)-(A), (iii)-(B), and (iv)-(C)

Ans. (b) Pseudocoelomate

Ans. (c) (A)-(i), (B)-(iii), (C)-(v), (D)-(iv), (E)-(ii)

Chordates	Non-chordates
(i) Notochord is present in at least one stage of the life cycle.	(i) Notochord is absent.
(ii) Pharyngeal gill slits are present	(ii) Pharyngeal gill slits absent.
(iii)  Post anal tail is present.	(iii) Post anal tail is absent.
(iv) Heart is ventrally located.	(iv) Heart (if present) is dorsally located.
(v) Cent ra l  nervous system is dorsally located and is hollow.	(v) Central nervous  system is ventrally located and is solid.

(i) Coelomate: There are two germinal layers in coelomates, viz. ectoderm, mesoderm and endoderm. The mesoderm lines the body cavity ad thus body cavity  is
present.
(ii) Acoelomate: There are two germinal layers in acoelomates, viz. ectoderm and endoderm. Body cavity is not present in coelomate.
(iii) Pseudocoelomate: There are three germinal layers in pseudocoelomate, viz. ectoderm, mesoderm and endoderm. But mesoderm is present as scattered
pouches and hence true coelom is absent. 

(i)  Amphibia
(a) Habitat: They live in freshwater and marine water. They can also live on land.
(b) External Features: Body is divided into head and trunk. Tail may be present in some. Skin is moist and has no scales. Eyes have eyelids. Tympanum represents
the ear.
(ii) Reptilia
(a) Habitat: They are primarily terrestrial animals. However, some are found in  aquatic habitat as well. But they cannot breathe under water. Limbs are in two pairs. 
(b) External Features: Skin is dry and covered with cornified scales. Tympanum represents the ear. Limbs (if present) are in two pairs. 

It is true that mammals are most adapted among vertebrates. Following are some of the adaptions shown by mammals:
(i) Mammals can be found in almost all types of habitat, e.g. in mountains, deserts, grasslands, plains and even in aquatic habitat.
(ii) Mammals have two pairs of limbs which help in running, jumping, walking, flying, climbing and burrowing.
(iii) Mammalian skin is equipped with sweat glands which help in osmoregulation and thermoregulation.
(iv) Hairs on skin provide insulation.
(v) External ears help in catching sound waves in efficient way.
(vi) Four-chambered heart facilitates double circulation which is more efficient than single circulation.
(vii) They are warm blooded animals which means they can control their body temperature.
(viii) Sexual dimorphism is well developed which is an important tool for survival. 
(ix) Most of the mammals are viviparous. This helps in longer life span of mammals.  

For the classification of living organisms, common fundamental characteristics are considered.

If we consider specific characteristics, then each organism will be placed in a separate group and the entire objective of classification would not be achieved.

Classification of animals is also important in comparing different organisms and judging their individual evolutionary significance. If only a single characteristic is considered, then this objective would not be achieved.

There is a certain common fundamental feature that helps in classification of living organisms. The features that can be used in classification are as follows.

On the basis of above features, we can easily classify a specimen into its respective category.

Coelom is a fluid filled space between the body wall and digestive tract.

The presence or absence of body cavity or coelom plays a very important role in the classification of animals.

Animals that possess a fluid filled cavity between body wall and digestive tract are known as coelomates. Annelids, mollusks, arthropods, echinodermates, and chordates are examples of coelomates.

On the other hand, the animals in which the body cavity is not lined by mesoderm are known as pseudocoelomates. In such animals, mesoderm is scattered in between ectoderm and endoderm. Aschelminthes is an example of pseudocoelomates.

In certain animals, the body cavity is absent. They are known as acoelomates. An example of acoelomates is platyhelminthes.

Intracellular digestion	Extracellular digestion
The digestion of food occurs within the cell.	The digestion occurs in the cavity of alimentary canal.
Digestive enzymes are secreted by the surrounding cytoplasm into the food vacuole	Digestive enzymes are secreted by special cells into the cavity of alimentary canal.
Digestive products are diffused into the cytoplasm.	Digestive products diffuse across the intestinal wall into various parts of the body.
It is a less efficient method.	It is a more efficient method of digestion.
It occurs in unicellular organisms.	It occurs in multicellular organisms.

Direct development	Indirect development
It is a type of development in which an embryo develops into a mature individual without involving a larval stage.	It is a type of development that involvesa sexually- immature larval stage, having different food requirements than adults.
Metamorphosis is absent.	Metamorphosis involving development of larva to a sexually- mature adult is present.
It occurs in fishes, reptiles, birds, and mammals.	It occurs in most of the invertebrates and amphibians.

Taenia (Tapeworm) and Fasciola (liver fluke) are examples of parasitic platyhelminthes.

Peculiar features in parasitic platyhelminthes are as follows.

1. They have dorsiventrally flattened body and bear hooks and suckers to get attached inside the body of the host.

2. Their body is covered with thick tegument, which protects them from the action of digestive juices of the host.

3. The tegument also helps in absorbing nutrients from the host’s body.

The phylum, Arthropoda, consists of more than two-thirds of the animal species on earth. The reasons for the success of arthropods are as follows.

1. Jointed legs that allow more mobility on land

2. Hard exoskeleton made of chitin that protects the body

3. The hard exoskeleton also reduces water loss from the body of arthropods making them more adapted to terrestrial conditions.

Water vascular system is a characteristic feature of the phylum, Echinodermata. It consists of an array of radiating channels, tube feet, and madreporite. The water vascular system helps in locomotion, food capturing, and respiration.

The characteristic features of the phylum, Chordata, include the presence of a notochord and paired pharyngeal gill slits. In sub-phylum Vertebrata, the notochord present in embryos gets replaced by a cartilaginous or bony vertebral column in adults. Thus, it can be said that all vertebrates are chordates but all chordates are not vertebrates.

Gas bladder or air bladder is a gas filled sac present in fishes. It helps in maintaining buoyancy. Thus, it helps fishes to ascend or descend and stay in the water current.

Birds have undergone many structural adaptations to suit their aerial life. Some of these adaptations are as follows.

(i) Streamlined body for rapid and smooth movement

(ii) Covering of feathers for insulation

(iii) Forelimbs modified into wings and hind limbs used for walking, perching, and swimming

(iv) Presence of pneumatic bones to reduce weight

(v) Presence of additional air sacs to supplement respiration

The numbers of eggs produced by an oviparous mother will be more than the young ones produced by a viviparous mother. This is because in oviparous animals, the development of young ones takes place outside the mother’s body. Their eggs are more prone to environmental conditions and predators. Therefore, to overcome the loss, more eggs are produced by mothers so that even under harsh environmental conditions, some eggs might be able to survive and produce young ones. On the other hand, in viviparous organisms, the development of young ones takes place in safe conditions inside the body of the mother. They are less exposed to environmental conditions and predators. Therefore, there are more chances of their survival and hence, less number of young ones is produced compared to the number of eggs.

The body segmentation first appeared in the phylum, Annelida (annulus meaning little ring).

(a) Operculum	(i) Ctenophora
(b) Parapodia	(ii) Mollusca
(c) Scales	(iii) Porifera
(d) Comb plates	(iv) Reptilia
(e) Radula	(v) Annelida
(f) Hairs	(vi) Cyclostomata and Chondrichthyes
(g) Choanocytes	(vii) Mammalia
(h) Gill slits	(viii) Osteichthyes

Answer:

S. No.	Name of organism	Phylum
1	Taenia solium	Platyhelminthes
2	Fasciola hepatica	Platyhelminthes
3	Ascaris lumbricoides	Aschelminthes
4	Wuchereria bancrofti	Aschelminthes
5	Ancyclostoma	Aschelminthes

(a)  In open circulatory system, blood flows in spaces called sinuses and cells and  tissues are directly  bathed in blood. In closed circulatory system, blood flows through a network of vessels. Arthropods and molluscs have open circulatory system, while annelids and vertebrates have closed circulatory system. 
(b) Oviparous animals lay eggs and young ones hatch from them after some time, e.g. reptiles, birds and some mammals. Viviparous animals give birth to young ones, e.g. scoliodon and most of the mammals.
(c) When the young ones are different from adult animals; this case is called indirect development, e.g. frog, cockroach, silkworm, etc. When the young ones resemble the adult animal; this case is called direct development, e.g. birds, mammals, reptiles, etc. 

Radial Symmetry: Coelenterates, Ctenophores and Echinoderms

Bilateral Symmetry: Annelids and Arthropods

There has been an increase in the n u m b e r  of chambers in heart during evolution of vertebrates. Give the names of the class of vertebrates having two, three or four chambered heart.

Phylum/Class	Excretory Organ	Circulatory Organ	Respiratory Organ
Arthropoda	Malpighian tubules	Open	Lungs/Gills/Tracheal System
Annelids	Nephridia	Closed	Skin/Parapodia
Mollusca	Metanephridia	Open	Gills
Amphibian	Kidneys	Closed	Lung

Column A	Column B
(a) Amphibia	(i) Air bladder
(b) Mammals	(ii) Cartilaginous notochord
(c) Chondrichthye	(iii) Mammary glands
(d) Ostichthyes	(iv) Pneumatic bones
(e) Cyclostomata	(v) Dual habitat
(f) Aves	(vi) Sucking and circular mouth without jaws.

Ans. (a) → (v), (b) → (iii), (c) → (ii), (d) → (i), (e) → (vi), (f) → (iv)

Endoparasites live in nutrient rich environment so most of their adaptations help them in maximizing absorption. In tape worm and round worm; there is an absorbent layer called tegument outside the body. This layer has villi-like structure which helps in better absorption of food. The endoparasites living in small intestine or large intestine get predigested food from their hosts so many of them may not have gut.
However, some of them have both gut and anus. 
Tapeworms also have suckers in mouth to absorb nutrients.

Endoparasites also show mechanisms to get transferred from one host to another. Sometimes, a part of their life cycle is spent in an intermediary host; such as in malarial parasite.
 

Animal	Characteristics
(a) Pila	(i) Jointed appendages
(b) Cockroach	(ii) Perching
(c) Asterias	(iii) Water vascular system
(d) Torpedo	(iv) Electric organ
(e) Parrot	(v) Presence of shell
(f) Dog fish	vi) Placoid scales