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 YZ X?

(a) Bird, lizard and dinosaur; Birds can fly ; Lizards can walk on walls; Dinosaurs can fly as well as walk too)

(b) Homologous organs. (Organs that have same structure but different function)


(c) Feathered Wings as in birds


(d) Tail as in reptiles


(e) YZ X?


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