Biology Class 11 NCERT Solutions: Chapter 4 Animal Kingdom Part 2

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


Taenia (Tapeworm) and Fasciola (liver fluke) are examples of parasitic platyhelminthes.

Peculiar features in parasitic platyhelminthes

Peculiar Features in 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.

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


The phylum, Arthropoda, consists of more than two-thirds of the animal species on earth.

Image of the arthropoda animal

Image of the Arthropoda Animal

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.

Reasons for arthropod success in image

Reasons for Arthropod Success in Image

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

(A) Porifera

(B) Ctenophora

(C) Echinodermata

(D) Chordate


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.

Water vascular system in image

Water Vascular System in Image

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


The characteristic features of the phylum, Chordate, include the presence of a notochord and paired pharyngeal gill slits. In sub-phylum Vertebrata, the notochord present in embryos get is 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.

Image of the Vertebrates vs. chordates

Image of the Vertebrates vs. Chordates

Q: 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.

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


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

Image of the some adaptations in birds

Image of the Some Adaptations in Birds

Q: 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. 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 compared to the number of eggs.

Image of the oviparous and viviparous animals

Image of the Oviparous and Viviparous Animals

Q: 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 (annulus meaning little ring).

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