Question

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, 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.

Answer 1

(a) The animal A could be a bird or a bat, animal B could be lizard, animal C could be human, animal D could be frog, animal E could be an insect.

(b) Forelimbs of A, B, C, and D are called homologous organs because they have the same basic structure but different functions.

(c) It suggests that these organisms have evolved from a common ancestor.

(d) It is because forelimbs of animal A and wings of animal E have different basic structures but perform a similar function.

(e) Animals A and E do not have a common ancestor.