NCERT Solutions for Class 11th: Ch 4 Animal Kingdom Biology

NCERT Solutions for Class 11th: Ch 4 Animal Kingdom Biology

Page No: 62


1. What are the difficulties that you would face in classification of animals, if common fundamental features are not taken into account?


If we consider specific characteristics instead of fundamental features 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.

2. If you are given a specimen, what are the steps that you would follow to classify it?


→ First Step: Look for the presence or absence of vertebral column.
→ Second Step: Identify the level of organization.
→ Third Step: Look for symmetry, i.e. radial or bilateral or asymmetrical.
→ Fourth Step: Look for presence or absence of body cavity.

3. How useful is the study of the nature of body cavity and coelom in the classification of animals?


The presence or absence of the body cavity gives a clue about a particular animal’s position in evolutionary ladder. The absence of coelom indicates that the animal is yet to develop a functional dividion of labour to carry out various activities. This indicates towards a simplicity of activities going on inside the body. The presence of coelom paves the way for evolution of a more complex and more efficient organ system for various activities.

4. Distinguish between intracellular and extracellular digestion?


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.

5. What is the difference between direct and indirect development?


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 involves a 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.

6. What are the peculiar features that you find in parasitic platyhelminthes?


Peculiar features in parasitic platyhelminthes are:
→ They have dorsiventrally flattened body and bear hooks and suckers to get attached inside the body of the host.
→ Their body is covered with thick tegument, which protects them from the action of digestive juices of the host.
→The tegument also helps in absorbing nutrients from the host's body.

7. What are the reasons that you can think of for the arthropods to constitute the largest group of the animal kingdom?


Arthropods are the first phylum to have well developed systems to carry out different activities. There is distinct system for respiration, locomotion and reproduction. Their survival capacity is great because of elaborate system. This has helped them survive in diverse conditions. This can be one of the reasons why arthropods are the largest group among the animal kingdom.

8. Water vascular system is the characteristic of which group of the following:
(a) Porifera (b) Ctenophora (c) Echinodermata (d) Chordata


(a) Porifera is having water vascular system. Food is gathered through movement of water and excretory products are expelled out of the body with the flow of water.

9. "All vertebrates are chordates but all chordates are not vertebrates". Justify the statement.


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.

10. How important is the presence of air bladder in Pisces?


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.

11. What are the modifications that are observed in birds that help them fly?


The modifications modifications in birds help them fly:
→ Streamlined body for rapid and smooth movement
→ Covering of feathers for insulation
→ Forelimbs modified into wings and hind limbs used for walking, perching, and swimming
→ Presence of pneumatic bones to reduce weight
→ Presence of additional air sacs to supplement respiration.

12. Could the number of eggs or young ones produced by an oviparous and viviparous mother be equal? Why?


The numbers of eggs produced by an oviparous mother will be more than the young ones produced by a viviparous mother 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.

13. Segmentation in the body is first observed in which of the following:
(a) Platyhelminthes (b) Aschelminthes (c) Annelida (d) Arthropoda


The body segmentation first appeared in the phylum, Annelida.

14.Match the following:
(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


(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

15. Prepare a list of some animals that are found parasitic on human beings.


Ascaris, Wucheraria, Acylostoma, Taenia, Fasciola.

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