Animal Kingdom Question Answers: NCERT Class 11 Biology

The phylum in which adults exhibit radicle symmetry and larva exhibit bilateral symmetry is Echinodermata. The radial symmetry of the adults is pentamerous, that is body parts are arranged in five. Then this has been secondarily derived from bilateral ancestral form. 

Ctenophores exhibit the phenomenon of bioluminescence which is the property of a living organism to emit light. They are marine and nearly transparent and some are brightly coloured. Animals Pleurobrachia, Beroe, Hormiphora etc. that belongs to Ctenophores.

(a) Frog (Amphibia)- Cold blooded animals are those which cannot regulate their internal body temperature according to the changing environment.

(b) Human (mammals)- Warm- blooded animals are those which can maintain and regulate their internal body temperature according to the changing environment. They can also adapt to harsh conditions of the environment.

(c) Lizard (Reptiles)- Scales are present and contains a waterproof protein keratin and checks loss of water, that enables reptiles to live on terrestrial or dry land. 

(d) Ascaris (Aschelminthes)- they generally show sexual dimorphism and are mostly dioecious. Males are usually smaller than the females. 

(a) Ascaris- The giant Intestinal Roundworm. It occurs in human small intestine and shows sexual dimorphism.

(b) Trygon- The Sting ray. It is found in all oceans. It is carnivorous and inflicts a painful wound with its spine that is present on the tail.  

(c) Snake- They belongs to the class Reptilia. They are long and contains cylindrical body, movable eyelids and tympana.

(d) Platypus (Ornithorhynchus)- Oviparous animals are those which lays eggs and look after their eggs after laying them. 

1. Haemocoel
2. Medusa
3. Nematocyst
4. Parapodia

(a)- (iii); (b)- (i); (c)- (iv); (d)- (ii)

Air sacs helps in respiration and buoyancy. Firstly respiration takes place only by the lungs and then they became spongy and inelastic. Thin- walled air sacs lying among the viscera that is associated with the lungs.

Pneumatic bones are hollow thus keep their body light and facilitate them in flying.

Metagenesis is also known as alternation of generation which shows between sexual and asexual reproduction. Cnidarian shows this type of phenomenon and exhibit two body types:

1. Polyp is cylindrical and fixed, but can be solitary or colonial.
2. Medusa is free swimming and umbrella like.

Cnidarians exhibit both forms and exhibit alteration of generation or we can say metagenesis in which polyp produces medusa by asexual method and medusa form the polyps by sexual method. Example: Obelia.

There are various important roles of feathers that are as follows:

1. They helps in maintaining the body temperature.
2. Feathers helps in attracting the males and females towards each other and plays important role in mating.
3. Feathers keep the body light and help in flight.

Cyclostomata is the group of chordates that have sucking and circular mouth without jaws. Cyclostomes belongs to agnatha craniates which lack jaws, paired appendages, pancreas and spleen. For example: Lampreys and hags.  

Placoid scales: Chondricthyes, i.e. Cartilaginous fish’s skin has unicellular epidermal mucous glands and dermal placoid scales. For example: Pristis- The true Sawfish, Trygon- the Sting ray, Torpedo- the Electric ray etc.

Cycloid scaled: Class Osteicthyes includes Bony fishes. Their skin has epidermal unicellular mucus glands and dermal cycloid, ctenoid and ganoid scales.  For example: Labeo rohita- The Carp (Rohu), Catla catla, Clarias batrachus- The Cat fish.

1. They show internal fertilization.

2. Their body is covered with dry and cornified skin without the glands. Scales are present and contains a waterproof protein keratin and checks loss of water, that enables reptiles to live on terrestrial or dry land. 

Chitinous exoskeleton: Arthropod’s body wall consists of thick, Chitinous cuticle and single- layered epidermis. The hard cuticle restricts growth and is periodically changed during growth. Example: Cockroach.

Calcareous shell: Phylum Mollusca contains external slimy shell which is usually secreted by mantle. Example: Pila.

Buccal cavity contains a rasping organ that helps in feeding, the radula with transverse rows of teeth. Radula helps in scratching and scraping the food.

Common Fundamental characteristics are considered for the purpose of classification of animals.

If we consider specific characteristics, 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.

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.

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

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 as compared to the number of eggs produced by oviparous mother.

The body segmentation first appeared in the phylum, Annelida (annulus meaning little ring).

            Column I                              Column II

(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

There is a certain common fundamental feature that helps in classification of living organisms. The features that can be used in classification for a given specimen are as follows.

On the basis of above features, we can easily classify a specimen into its respective category.

Coelom is a fluid filled space between the body wall and gut wall and lined by mesoderm on all of its sides. 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 pseudocoelomates. In such animals, mesoderm is scattered in between ectoderm and endoderm. Aschelminthes is an example of pseudocoelomates. In certain animals, the body cavity is absent. They are known as acoelomates. An example of acoelomates is platyhelminthes.

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

The phylum Arthropoda consists of more than 75% of the animal species found on this earth. 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.

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.

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. But in cephelochordates, notochord persists throughout life as such and in urochordates, notochord is present only in larval stages and absent in adults. Thus, it can be said that all vertebrates are chordates but all chordates are not vertebrates.