Analogous Organs are those organs of different animals that although look different in structure but perform a common function. These organs are evolved from a Convergent Evolution, that is, the ancestors of these animals are not similar but they are now evolving in the same ecological niche as the other animal. When unrelated organisms form a related biological characteristic, it is called Convergent Evolution.
Therefore this type of evolution of two or more animals in which they do not have a common ancestor, and hence different anatomy of their body parts/organs, but have a common ecological niche resulting in a similarity of their uses is called as convergent evolution and these types of organs are called as Analogous Organs.
Definition of Analogous Organs:
Analogous Organs are defined as the organs of different animals having different anatomy but performing the same function. These animals have different origins and different ancestors.
Examples of Analogous organs:
Wings of Birds, Bat and Butterfly
All these three organs are different in their structures. The wings of the birds are formed from bones which are covered by their feather. The wings of the insects, however, like a butterfly, are an extension of their integuments and the wings of the bats are mainly the folded skin along with their elongated fingers. Hence all the three organs are different in their structures but all are used for one common function, that is flying. Therefore called as Analogous Organs.
Sweet Potato and Potato
These two plant structures are different in their anatomy. The sweet potato is a modification of the roots while the Potato is a modification of the stem. But both these organs are used for the same function, that is the storage of food by the plant making them Analogous Organs.
Eye of an Octopus and a mammal
These two organs are also an example of the convergent evolution. Although morphologically, these two organs may look similar to each other, there is a notable difference in their structures. For example, the difference in focusing light on the retina by octopus eye and mammalian eye. The eye lens of mammals focus light by changing the shape of the lens using ciliary muscles, octopuses, on the other hand, move the focus of the light by moving their lenses farther and closer to their retina, similar to a camera lens. Therefore the eyes of octopuses are also referred to as ‘Camera Eyes’. Another difference is in the cellular structure of the octopus eye and a mammalian eye. But both the organs perform a related function, that is focusing the light on the retina, and are therefore an example of Analogous Organs.
Flippers of Penguin and Dolphin
Penguins and Dolphins are evolved from different origins therefore they are an example of Convergent Evolution. Dolphins are evolved from the mammals that walk of the land while penguins are evolved from the birds that fly. But both these organisms emerged a common structure called flippers to swim underwater. The function of the flippers are similar and hence these are an example of Analogous Organs.
Cactus and Euphorbia
Both these plants have different morphology and anatomy but both have photosynthetic stems and their leaves are also modified into spines. As both are succulent plants, their spines are used to reduce the extra loss of water in arid climate or soil conditions.
Pyracantha (firethorn) and Berberis (barberry)
Both these plants have thorns for protection but the thorns of Firethorn have modified stem while the thorn of Barberry is modified leaves. Therefore these are also an example of the Analogous Organs.