Question

X, Y, and Z are three animals. The animal X can fly but animal Y can only run on ground or walls. The forelimbs of animals X and Y have the same basic design but they are used for different purposes such as flying and running respectively. The animal Z became extinct a long time ago. The study of fossils of Z tells us that it had some features like those of X and some like those of Y. In fact, Z is said to form a connecting link in the evolutionary chain of X and Y.
(a) What could the animals X, Y and Z be?
(b) What name is given to the forelimbs like those of X and Y which have the same basic design but different functions?
(c) Name one feature in which Z resembled X.
(d) Name one feature in which Z resembled Y.
(e) Which is the correct evolutionary chain involving X, Y and Z X → Z → Y or Y → Z → X?

Answer 1

Homologous organ and use of forelimbs

Explanation:

• Homologous organs may be determined as the organs of animals which have some similar basic structure but their function is different to each other.
• The function of forelimb is different in every individuals .Besides walking in four footed animals they are for digging too.
• (a) X is birds, Y is reptiles and Z is Archaeopteryx.
• (b) Forelimbs like those of X and Y are called homologous organs.
• (c) X and Z had feathers.
• (d) Z had teeth and tail like Y.
• (e) The correct evolutionary sequence is Y → Z → X.