Question

Using appropriate terminology, explain how homologous structures such as the limbs of humans, cats, whales and bats provide evidence for evolutionary theory.

Answer 1

Homologous structures have similar basic structures but perform different functions (may or may not have the same functions). Limps of humans, cats, whales, and bats are the best examples of homologous structures. These all have a similar basic pattern of bones because they were inherited from a common ancestor. They perform different functions because they are adapted to function in different environments.

Even though they have different sizes and shapes, they have a similarity in their structure i.e., they have the same set of bones. For example, the forelimbs of humans, whales, cats, and bat have different sizes and shape but they have the same set of bones in it. They also perform various functions, for example, the function of the human forelimb is to hold things, the function of the forelimb of cat is to assist in its movement, The forelimb of the whale act as flippers and bats forelimbs are modified for flying. The presence of all these homologous organs indicates that all these species are evolved from a common ancestor. i.e., homologous organs indicate that they had the same ancestor with the basic design of the organ in which all the homologous organs are based.

Homologous organs provide the evidence for divergent evolution (Also called adaptive radiation). It is the development of functional structures from a common ancestor, which means diverging from a single point.

In short, we can understand from homologous organs of related species, that they all are descended from a common ancestor. But adapted to different environments so they perform various functions.