Class 11 Biology

Animal Kingdom

NCERT Solution

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

Answer: Using the common fundamental features helps in segregating the animals in different groups. Let us take the example of presence or absence of notochord. This feature helps us in grouping the animals among chordates and non-chordates. Similarly, two or three embryonic layers are taken for grouping the animals under diploblastic and triploblastic categories. Use of fundamental features in classification paves the way for further segregation of animals among different sub-groups.

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

Answer: Steps to Follow for Classification:

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

Answer: The nature of coelom 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.

Question 4: Distinguish between intracellular and extracellular digestion?

Answer: In case of intracellular digestion, digestion takes place inside the cell. Digestive enzymes are secreted in the food vacuole where food is digested. Absorption and assimilation are also intracellular in this case. Food is simple in this case.

In case of extracellular digestion, digestion takes place outside the cell. A rudimentary or developed alimentary canal may be present for facilitating extracellular digestion. Extracellular digestion is more evolved than intracellular digestion. Complex food can be utilised in this case.

Question 5: What is the difference between direct and indirect development?

Answer: When the young one resembles the adult animal, then it is the case of direct development. But when the young one looks entirely different than the adult animal, it is the case of indirect development. An animal may pass through several forms during indirect development, e.g. frog and silk moth.

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

Answer: Hooks and suckers are present in parasitic platyhelminthes. Suckers facilitate the sucking of blood from the host.

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

Answer: Arthropoda is the first phylum in which animals have properly developed organ systems. Elaborate organ system helped the arthropods in surviving in diverse conditions. Moreover, the arthropods are the earliest among the animals with well developed organ system. These are the reasons that arthropoda is the largest phylum in the animal kingdom.

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

Answer: (a) Porifera and (c) Echinodermata

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

Answer: Presence of notochord at some stage of life is the key feature of chordates. Notochord is present in vertebrates in the embryonic stage and hence all vertebrates are chordates. But in some of the chordates, notochord may persist throughout the life. Hence, all chordates are not vertebrates.

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

Answer: Air bladder helps the bony fishes in buoyancy.

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

Answer: Following are the modifications in birds that help them fly:

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

Answer: In case of oviparous animals, eggs are exposed to the vagaries of nature and also face the danger of predators. Hence, a larger number of eggs needs to be laid to ensure survival of the species.

In case of viviparous animals, the foetus develops to a size that it can have better chances of survival after birth. Moreover, development of foetus requires more resources from the female’s body. Hence, a smaller number of offsprings are produced by viviparous animals.

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

Answer: (c) Annelida

Question 14: Match the following:

Column IColumn II
(a) Operculum(1) Ctenophora
(b) Parapodia(2) Mollusca
(c) Scales(3) Porifera
(d) Comb plates(4) Reptilia
(e) Radula(5) Annelida
(f) Hairs(6) Cyclostomata and chondrichthyes
(g) Choanocytes(7) Mammalia
(h) Gill slits(8) Osteichthyes

Answer: (a) 8, (b) 5, (c) 4, (d) 1, (e) 2, (f) 7, (g) 3, (h) 6

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

Answer: Ascaris, Wucheraria, Acylostoma, Taenia, Fasciola