Examples of Homologous and Analogous Structures

What do you mean by homologous structures? Well, homology represents common ancestry. In other words, when we say homologous structure, it means we are talking about two structures which have a similar origin. However, it is important to mention that though two structures have a similar origin, that does not mean they will have a similar and function as well. For instance, thorn and tendrils of Bougainvillea and Cucurbita. Both are modifications of stem buds, but they perform different functions. For example, a thorn is a structure for protection while tendrils are structures for climbing and support to the substratum.

If we take an example in animals, humans, cheetah, whale, and bat show similar anatomical structure -- all of them possess humerus, radius, ulna, carpals, metacarpals, and phalanges, but they perform different functions.

Besides, homology represents divergent evolution because though their origins are same, but their structure and functions are different.

Now, let's discuss about analogous structures. Well, an analogy is just the opposite of homology meaning, two structures show analogy when they have a different origin, but similar structure and function. For instance, the eye of octopus and mammals; flipper of penguins and dolphins. sweet potato (root modification) and potato (stem modification). 

Octopus belongs to the phylum Mollusca and cat belongs to the phylum Mammalia. However, both possess eyes which have a similar structure and function. Besides, analogous structure leads to convergent evolution because though they have a different origin, but structurally and functionally, they are the same. 

Q. What do you think about vertebrate heart and brains? Do they show homology or analogy?

Ans: Both vertebrate heart and brain show homology. For example, chicken heart and fish heart show homology because they evolved under common ancestry as they show structures like auricle and ventricle. On the other hand, vertebrate brains are divided into forebrain, midbrain, and hindbrain - common subdivisions of the brain in all vertebrate animals. 

Now, I let you think about other homologous and analogous structure.

Heart of Fish and Heart of Crocodile

Wings of butterfly and wings of birds

Thorns of Bougainvillea and spines of Opuntia

Please write your answer in the comment box.