Evidence from comparative anatomy of evolution - Analogous organ, Analogy

 

Before this post we have discussed the homologous organ, now we will discuss the analogous organ. In contrast to homologous organs, the analogous organs are similar in structure and origin but they perform a different kind of function. 

The organisms that have the analogous organs have no blood relationship. These are widely different in terms of phylogenetically but they may have adapted themselves in similar habitats and modes of life.Thus analogous organs show evidence of convergent evolution or adaptive radiation. The analogous organ also shows the  parallel evolution because this can be noticed in certain closely related species.

Example of analogous organ

Most of the insects have  wings because they have adapted in aerial life like the flying lizard bird and birds. The wings of insects look like the wings of flying vertebrates but there are  more differences between the wings of insects and vertebrates in terms of structure. There are no bone in wing of insect thus insect win are  analogous to vertebrate wing. Beside this, 

Insect Wings are composed of chitin.  whereas the wing of the vertebrates like the birds are the modification of the forelimb and are composed of bone. Therefore there are basic differences in the origin of the wings of insects and the birds, therefore they are examples of analogous organs.

Whales and seals are mammals which are adopted in marine life during the course of evolution. The pentadactyl limbs are called flippers. These flippers are modified for swimming and assume the  analogy with fins of fish because fins of fish are not pentadactyl.Thus flippers of whale and seal as well as fin of the fish are totally different in structure but perform the common function like swimming hence they are analogous organs. 

Sting of honey bee and Scorpion perform the similar function and look alike. These are analogous organs. The sting of a honey bee is the modification of its ovipositor.  while the sting of  Scorpion is a modification of the last abdominal segment. 

The Eyes of octopus and mammals are also examples of analogous organs. Both eyes are used in function of the vision but both are different in their structure and origin. 

Similarly in plants, if we observe sweet potato and the potato, both are used to store food in form of starch and become swelling under the ground but sweet potato is the modification of root whereas potato is the modification of stem. Thus they also show convergent evolution.