Q. 673.7( 3 Votes )
There are five animals A, B, C, D and E. The animal A uses its modified forelimbs for flying. The animal B uses its forelimbs for running whereas the animal C uses its forelimbs for grasping. The animal D can live on land as well as in water and uses its forelimbs to prop up the front end of its body when at rest. The animal E which respires by using spiracles and tracheae uses wings for flying but its wings are analogous to the modified forelimbs of animal A.
(a) What could the animals A, B, C, D and E be?
(b) Why are the forelimbs of animals A, B, C and D called homologous organs ?
(c) What does the existence of homologous organs in animals A, B, C and D tell us about their ancestors?
(d) Why are the modified forelimbs of animal A and the wings of animal E called analogous organs?
(e) State whether animals A and E have a common ancestor or not.
(a)Animals A, B, C, D and E could be sparrow, Lizard, human, frog, insect.
(b) Forelimbs of Bird, lizard, human and frog are called homologous organs because their basic structure of bones is similar but they perform different functions. This means that they have had a common ancestor and with time they adapted themselves according to the requirements.
(c) The existence of homologous organs in animals A, B, C, D tell us that since they have similar basic structure of origin, they have a common ancestor.
(d) Modified forelimbs of Bird and wings of Insect are called analogous organs because they have different basic structure but they perform similar functions. Bird uses its forelimbs to fly; similarly insect uses its wings to fly. Because their basic structure of origin is different so they do not have a common ancestor.
(e) No, Animals having analogous organs do not have a common ancestor because their basic structure of origin is different.
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