Question

The bones of forelimbs of whale, bat, cheetah and man are similar in structure , because
A. One organism has given rise to another
B. They share a common ancestor
C. They perform the same function
D. They have biochemical similarities

Answer 1

Homologous organs are given as the forelimbs of whale, bat, cheetah and man are homologous which have similar structure but not the same function. Homologous organs are given in the question as the bones of forelimbs of whale, bat, cheetah and man are similar in structure and homologous organs means the organs having the same structures but their functions are different.

Complete answer:
During the development, these organs are developed similar which results in their similar structure but in the adult condition, these organs become modified due the adaptations according to the environment and they start to perform different functions because of these adaptations. Now we can say from this explanation that these structures are a result of evolution.
Now if we look at options, Option A is One organism has given rise to another but this is totally incorrect as same species of organisms can give rise to the same species, for example, whale give rise to whale, bat give rise to bats, cheetah give rise to cheetah, man give rise to man. Their structures are similar because they share a common ancestor.
Moving to option B which is they share a common ancestor. It is the correct one since this is the reason that the structure of their forelimbs bones are similar because of their common ancestors/ forefather. These are called homologous organs which have similar structure but different functions.
Moving to option C which is they perform the same function. This is totally incorrect since these are homologous and they have similar structures but they perform different functions not the same function. Therefore, it is incorrect.
Last option is D which has biochemical similarities. This option is incorrect as the structure of forelimbs are similar because they share common ancestors. This option is thus incorrect.

Thus, the correct option is B which is that they share a common ancestor.

Note: Homologous organs are those organs which are similar in structure but they do not perform the same structures and that is what is given in the question since the forelimbs of whale, man, bat, cheetah do not perform the same function. All of them perform different functions but their structures are similar because of their common ancestors.