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?

Answer.  For the classification of living organisms, common fundamental characteristics are considered. Animal classification would be very confusing if fundamental features are not considered.
(i) Animals having different levels of organisation would have been placed in same group. E.g., Sponges and Cnidarians having same cellular and tissue level of organisation respectively.
(ii)Animals showing different types of germinal layers would have been placed together, as diploblastic cnidarians and triploblastic platyhelminthes.
(iii)Animals having different body symmetry would have been placed together, as coelenterates with radial symmetry and platyh elminthes with bilateral symmetry.

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

Answer. Various steps considered to classify a specimen are
(A)Mode of nutrition – It can be autotrophic, holozoic, saprophytic or parasitic.
(B)Complexity of body structure – Whether the specimen is unicellular or multicellular.
(C)Presence or absence of membrane bound organelles.
(D)Body symmetry, i.e., the plane by which organism can be divided into two equal halves.
(E)Presence or absence of coelom, it can be acoelomates, pseudoco elomates, eucoelo- mates.
(F)Phylogenetic relationship.

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

Answer. 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 pseudoco elomates. In such animals, mesoderm is scattered in between ectoderm and endoderm. Asch elminthes is an example of pseudoco elomates. In certain animals, the body cavity is absent.

4. Distinguish between intracellular and extra-cellular digestion.

Answer. Differences between intracellular and extracellular digestion are:

Intracellular digestionExtracellular digestion
The digestion of food take place within the cell.The digestion take place outside the cell 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.
Products of digestion are diffused into the cytoplasm.Products of digestion diffuse across the intestinal wall into different parts of the body.
It is a less efficient method and it does not show the regional differentiation.It is a more efficient method and shows the regional differentiation.
It occurs in unicellular organisms.It occurs in multicellular organisms.

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

Answer.  Differences between direct development and indirect development are :

Direct developmentIndirect 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.
Meta morphosis is absent.Meta morphosis involving development of larva to a sexually-mature adult is present.
Inter mediate stages are absentInter mediate stages are 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  platyh elminthes?

Answer. Following are the peculiar features of parasitic platyh elminthes:
(i) The thick tegument (body covering) resistant to the host’s digestive enzymes and anti-toxins.
(ii)Adhesive organs like suckers in flukes and the hooks and suckers in tape worms for a firm grip on or in the host’s body.
(iii)Loss of locomotory organs.
(iv)Digestive organs are absent in tape worms because digested and semi digested food of the host is directly absorbed’ through the body surface.
(v) Reproductive system is best developed in parasitic flatworms.
(vi)Parasitic flatworms, such as liver fluke and tapeworms perform anaerobic respiration.
(vii)They possess a considerable osmotic adaptability, as they can successfully live in different media.

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

Answer.  The reasons for the success of arthropods are as follows.

• Jointed legs that allow more mobility on land

• Hard exoskeleton made of chitin that protects the body

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

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

Answer. (c) Echin odermata

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

Answer.  Chordates are the animals that possess notochord (a stiff, supporting rod like structure present on the dorsal side) at some stage of their lives. Phylum Chordata is divided into three Subphyla: Uroch ordata or tunicata, Cephal ochordata and Vertebrata. Subphyla Urochordata and Cephalochordata are often referred to as protochordates and are exclusively marine. In urochordata, notochord is present only in tail of larva and disappears in adults, while in cephalochordata, it extends from head to tail region and persists throughout the life.
The members of Subphylum Vertebrata a possess notochord during the embryonic period and is replaced by a cartilaginous or bony vertebral column in the adult. Thus all vertebrates are chordates but all chordates are not vertebrates.

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

Answer. Bony fishes have a sac-like outgrowth, the swim bladder also called air bladder, that arises as an outgrowth from the dorsal wall of oesophagus. It is hydrostatic in function. It regulates buoyancy and helps them to swim up and down, thus preventing them from sinking. In some species air bladder also helps in respiration. It also serves as resonating chamber to produce or receive sound.

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

Answer.  Birds have adapted to aerial mode of life through the following modifications:

• 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?

Answer. No, the number of eggs or young ones produced by an oviparous and viviparous mother respectively cannot be equal. Oviparous mother lays large number of eggs, as the eggs are laid outside the body, so they are not protected from predators and harsh environmental conditions, and therefore destroyed. However in viviparous mother, eggs are not laid outside, but the embryos develop inside the mother and thus are protected from the outside harsh environment, thus, the number of eggs produced are less. Therefore, the number of eggs or young ones produced by an oviparous and viviparous mother respectively cannot be equal.

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

Answer. (c) Annelida

14.Match the following:

Answer. (a) – (viii), (b) – (v), (c) – (iv), (d) – (i), (e) – (ii), (f) – (vii), (g) – (iii), (h) – (vi).

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

Answer. List of some animals that are found parasitic on human beings :

NCERT solutions for class 11 biology Chapter 4 Animal Kingdom