NCERT Solutions for Class 11 Biology Chapter 4: Animal Kingdom

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

Ans. Animals are classified on the basis of common characteristics such as cell organisation, body symmetry, coelom type, digestive tract, circulation, and reproductive system. It is very difficult to handle each living thing uniquely without these common traits. It is also a tedious task to add new species discovered every day
without including these common features. Therefore, to investigate animal diversity, classification must be based on common fundamental features.

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

Ans. There are some fundamental features that help in the classification of living organisms and the features that can be used in classification are as

(a) Level of classification: Cellular, tissue, or organ level.

(b) Body cavity: Absent or present.

(c) Type of body symmetry: Radial or bilateral

(d) Type of coelom development: Acoelom, Pseudocoelom and true coelom.

(e) Type of true coelom: Enterocoelom and Schizocoelom.

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

Ans. The nature of coelom or body cavity gives important clue for classification of animals. The absence of coelom means that the animal has not developed a division of labour for various biological activities. On the other hand, the presence of coelom shows further evolution from simple to more complex organism.

4. Distinguish between intracellular and extracellular digestion?

Ans. Difference between intracellular and extracellular digestion:

Intracellular Digestion Extracellular Digestion
  1. It occurs within the cell.
It occurs in cavity of alimentary canal.
  1. 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.
  1. It is less efficient method of digestion.
It is more efficient method of digestion.
  1. It occurs in unicellular organisms.
It occurs in multicellular organisms.

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

Ans. Difference between direct and indirect development:

Direct Development Indirect Development
  1. It is a type of development in which an embryo develops into a mature individual without undergoing a larval stage.
It is a type of development that involves a sexually-immature larval stage, having different food requirements than adults.
  1. Metamorphosis does not occur.
Metamorphosis occurs.
  1. It occurs in fishes, reptiles, birds and mammals.
It occurs in most invertebrates and amphibians.

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

Ans. The parasitic Platyhelminthes have following features:

(a) They have dorso-ventrally flattened body, hence are called flatworms.

(b)  These are mostly endoparasites found in animals including human beings.

(c) Flatworms are bilaterally symmetrical, triploblastic and acoelomate animals with organ level of organisation.

(d)  Hooks and suckers are present in the parasitic forms.

(e) Some  of them absorb nutrients from the host directly through their body surface.

(f) Specialized cells called flame cells help in osmoregulation and excretion.

(g) Sexes are not separate.

(h) Fertilization is internal and development is through many larval stages.

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

Ans. The phylum Arthropoda consists of about 80% of the total animals in animal kingdom. The reasons for arthropods being the largest group are as follows:

(a) They have joint legs that allow more mobility on land.

(b) Their exoskeleton is hard which is made up of chitin that protects the body.

(c) The hard exoskeleton reduces water loss from the body and thus making them more adapted to terrestrial conditions.

8. Water vascular system is the characteristic of which group of the following:

(a) Porifera

(b) Ctenophora

(c) Echinodermata

(d) Chordata

Ans. 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.

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

Ans. The characteristic features of all chordates is the presence of a notochord. Chordates include Urochordates, Cephalochordates (both are called Protochordates) and vertebrates. In vertebrates, notochord is replaced by vertebral column (backbone). However, vertebral column is not present in Protochordates. Therefore, all the vertebrates are chordates but all chordates are not vertebrates.

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

Ans. Air bladder is a gas-filled sac present in fishes. The function of air bladder is to maintain buoyancy while fish is swimming. 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?

Ans. Birds have several structural modifications to suit their aerial life. Some of these modifications are as follows.

(a) They have streamlined body for rapid and smooth movement.

(b) The body is covered with feathers for insulation.

(c) Their forelimbs are modified into wings and hind limbs used for walking, perching and swimming.

(d) They have light and hollow bones to reduce weight.

(e) Their body has 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?

Ans. The number of eggs produced by oviparous and viviparous mothers cannot be equal. This is because the number of eggs produced by oviparous mothers is more. The reason is that in oviparous animals, fertilization takes place outside the body whereas in viviparous animals, development takes place inside the body which is a protective environment. In case of oviparous animals, the eggs are present outside, so they are exposed to risk by eaten away by the predators. So, these animals produce more eggs to sustain their progeny.

13. Segmentation in the body is first observed in which of the following:

(a) Platyhelminthes

(b) Aschelminthes

(c) Annelida

(d) Arthropoda

Ans. The body segmentation or metamerism first appeared in the phylum Annelida. They demonstrate the division of the body into a linear series of cylindrical segments from head to tail. So, the correct answer is option (c).

14. Match the following:

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

Ans. The correct matching is following:

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

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


Name of organism Phylum In parts of human body
  1. Taenia solium
Platyhelminthes Intestine
  1. Fasciola hepatica
Platyhelminthes Liver and bile duct
  1. Ascaris lumbricoides
Aschelminthes Small intestine
  1. Wuchereria bancrofti
Aschelminthes Lymphatic and muscular system
  1. Ancyclostoma
Aschelminthes Small intestine