Animal Kingdom Question Answers: NCERT Class 11 Biology

Common Fundamental characteristics are considered for the purpose of classification of animals.

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.

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 as compared to the number of eggs produced by oviparous mother.

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

            Column I                              Column II

(a)       Operculum                (viii)   Osteichthyes

(b)       Parapodia                  (v)       Annelida

(c)       Scales                         (iv)      Reptilia

(d)       Comb plates              (i)        Ctenophora

(e)       Radula                        (ii)       Mollusca

(f)        Hairs                           (vii)    Mammalia

(g)       Choanocytes             (iii)     Porifera

(h)       Gill slits                     (vi)      Cyclostomata and Chondrichthyes

There is a certain common fundamental feature that helps in classification of living organisms. The features that can be used in classification for a given specimen 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 gut wall and lined by mesoderm on all of its sides. 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.

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 75% of the animal species found on this earth. The reasons for the success of arthropods are as follows.

i. Jointed legs that allow more mobility on land

ii. Hard exoskeleton made of chitin that protects the body

iii. 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. But in cephelochordates, notochord persists throughout life as such and in urochordates, notochord is present only in larval stages and absent in adults. Thus, it can be said that all vertebrates are chordates but all chordates are not vertebrates.

1. Aves and Mammals: Both Aves and Mammals are warm- blooded and have 4- chambered heart.
2. A Frog and Crocodile: Both are cold blooded and are oviparous.
3. A Turtle and Pila: Both are cold blooded and are oviparous animals.

1. Icthyophis- It is a limbless amphibian.
2. Trygon (Sting ray), Frog (Amphibia)- Cold blooded animals are those which cannot regulate their internal body temperature according to the changing environment.
3. Macaca (monkey), Human (mammals)- Warm- blooded animals are those which can maintain and regulate their internal body temperature according to the changing environment. They can also adapt to harsh conditions of the environment.
4. Naja (Cobra)- Most of the reptiles contain rough and dry skin.
5. Euspongia (Bath sponge)- Phylum Porifera contains body cavities: large cavities are the spongocoel and small cavities are the canals.
6. Hydra- Cnidarians contain stinging cells for offence and defense. 

a. Panthera Leo

Viviparous are those animals that gives birth to the live young ones. They show parental care after their birth.

b. Trygon

The Sting ray. It is carnivorous and inflicts a painful wound with its spine that is present on the tail.

c. Torpedo

The electric ray. It stuns or kills the prey and enemies with electric shock from the electric organs.

d. Air bladder

e. Obelia

f. Echidna and Platypus (Ornithorhynchus)

Oviparous animals are those which lays eggs and look after their eggs after laying them. They contains mammary glands.

pending

1. Haemocoel
2. Medusa
3. Nematocyst
4. Parapodia

(a)- (iii); (b)- (i); (c)- (iv); (d)- (ii)

Presence or absence of a cavity between the body wall and gut plays an important role in classification. There are three layers endoderm (inner layer), the ectoderm (outer layer) and the mesoderm (middle layer).

Organism that possess coeloms or a complete fluid filled cavity between the body wall and the digestive tract which is lines by mesoderm is called coelomates. Example: echinoderms, hemichordates and chordates.

Organisms in which, the body cavity is not lined by mesoderm or mesothelium; is also termed ‘the false coelom or pseudocoel’, and the mesoderm is present in the form of scattered pouches in between ectoderm and endoderm are called Pseudocoelomate. Example: Aschelminthes (roundworms).

Organisms in which the body cavity is absent except that is in the digestive tract, are called acoelomates. Example: Platyhelminthes (flatworms).

Class- Amphibia

Habitat- Amphibians can live on both land and water.

External features:

1. They have very smooth skin (without scales), moist and are thin.
2. The eyes have eyelids. Ear is represented by tympanum.
3. They have pair of limbs. Body is divisible in head and trunk. Tail may be present in same. Example: Toad, Frog etc.
4. Respiration occurs by gills, lungs.
5. Contains 10 pairs of cranial nerves.

Class- Reptilia

Habitat- The class name refers to their creeping crawling mode of locomotion. They are mostly terrestrial (lives on land).

External features:

1. They are covered with dry and cornified skin and scales.
2. They do not have external ear opening. Ear is represented by tympanum.
3. They have pair of limbs. Example: Crocodile, Turtle etc.
4. Respiration occurs by lungs.
5. They have four chambered heart.
6. Excretory system contains kidneys.
7. Contains internal fertilization.

Mammals are most adapted among the vertebrates. Some of the reasons are as follows:

1. Mammals are found in the variety of habitats like polar ice caps, deserts, mountains, forests, grasslands and dark caves. Some of them are adapted to fly and swim.
2. They have mammary glands that produce milk to nourish their young ones.
3. They are warm- blooded means they are capable to maintain their body temperature in different conditions.
4. They differ in the type of jaws and sexes are separate and fertilization is internal.
5.  They use their pair of limbs for walking, burrowing, climbing etc. they are viviparous with few exceptions and development is direct.
6. They have four- chambered heart.
7. The skin of mammals is unique in possessing hair. Their external ear are present.
8. Respiratory organ is lung and excretory organ is kidney. They reproduces sexually. They breathe oxygen and release carbon dioxide.
9.  Their brains are more developed. Example: Humans, Whales, Dogs etc.

(a)- (v); (b)- (iii); (c)- (ii); (d)- (i); (e)- (vi); (f)- (iv)

• Amphibia lives on terrestrial as well as in aquatic habitat.
• Mammals contains milk- secreting mammary glands in the females for suckling the young ones for some time after birth.
• Chondricthyes, i.e. Cartilaginous fish’s skin has unicellular epidermal mucous glands and dermal placoid scales.
• Class Osteicthyes includes Bony fishes. Their skin has epidermal unicellular mucus glands and dermal cycloid, ctenoid and ganoid scales. Swim bladder is used as a lung for breathing air.
• Cyclostomata is the group of chordates that have sucking and circular mouth without jaws and belongs to agnatha craniates.
• Pneumatic bones are hollow thus keep their body light and facilitate them in flying.

Special structures or adaptations that enables them to survive in extreme conditions are:

1. High reproductive capacity.
2. Presence of adhesive organs or suckers to cling on the host.
3. Loss of digestive system.
4. Loss of sensory organs.

(a)- (5); (b)- (1); (c)- (3); (d)- (4); (e)- (2); (f)- (6)

a. Open circulatory system: Blood is directly circulated in the cells and tissues without any network of vessels. Example: Mollusca, Arthropoda.

Closed circulatory system: Blood is circulated through a proper network of vessels (arteries, veins and capillaries). Example: Annelida and Chordata.

b. Oviparous: Oviparous are the animals that lay eggs. Oviparous animals or organisms look after their eggs after laying them.

Example: Birds, Reptilia.

Viviparous: are those animals that gives birth to the live young ones. They show parental care after their birth.

Example: Mammals.

c. Direct development: In this development larval stage is not present. An embryo develops into a mature individual without involving larval stage. Example: Human beings.

Indirect development: In this development sexually immature larval stage is present. Example: Butterflies.

d. Acoelomate: The animals in which the body cavity is absent. Example: Poriferans, Ctenophores.

Pseudocoelomate: The animals in which the body cavity is not lined by mesoderm layer and mesoderm is present in scattered pouches in between ectoderm and endoderm. Example: Aschelminthes.

e. Notochord: It is mesodermally derived rod- like structure formed on the dorsal side during embryonic development.

Nerve cord: Nerve cord is a strand of nervous system.

f. Polyp: Poly is sessile and cylindrical form. Example: Hydra, Adamsia.

Medusa: Medusa is free swimming and an umbrella shaped structure. Example: jelly fish.  

a. Chondricthyes: They have cartilaginous endoskeleton. Their gills are not covered by operculum. They are mainly marine and their body is streamlined. They are predaceous. Due to the absence of air bladder, they have to swim constantly to avoid sinking. Example: Trygon, Scoliodon, Pristis etc.

Osteicthyes: They have bony endoskeleton. They are both marine and fresh water fishes. Their body is streamlined. Gills are covered with operculum, skin is covered with cycloid/ ctenoid scales. Air bladder is present which regulates buoyancy. Example: Labeo rohita, Catla catla.

b. Urochordata and Cephalochordata: In Urochordata, the notochord is present only in larval tail and disappears in adults. Example: Salpa, Herdmania etc. In Cephalochordates, notochord extends from head or tip of the snout to tail region and persists throughout the life. Example: Brachiostoma.