Question

Which one of the following is the correct example of homologous organs?
A. Human kidney and earthworm's nephridia
B. Bat's wings and horse's front legs
C. Human trachea and insect tracheae
D. Tendril of cucumber and tendril of Smilax

Answer 1

The homologous organs are defined as organs which are similar in form (or are embryologically same), but do different functions in different organisms. Hence, these provide strong evidence basis in the favour of evolution.

Complete answer:
You should know, the body consists of many organs. These organs are divided into two categories- homologous organs and analogous organs. Let us now learn about these different categories of organs.
Homologous Organs are referred to as the organs of different animals that have similar structure but perform different functions. The structure of the two different animals are the same, but the functions of their organs differ.
Take an example of homologous organs as- the forelimbs of frog, man, and the flippers of the whale.
Their structure in these animals are the same but the function in a different manner. The flippers are used to swim, the forelimbs of frogs are used to jump and prop, whereas the forelimbs of man are used for writing, eating, holding things, etc. Remember, by having a similar structure shows that all these animals must have a common ancestor.
Analogous Organs- are referred to as the organs of different animals that have different structures but perform the same functions. For example, the wings of the insect and those of the bird.
The structure of wings of the bird consist of bones covered by flesh, skin, and feathers. Whereas the wings of insects are believed to be an extension of integument. But in both the cases of birds and insects, the wings are used to fly. These organisms would have to go through adaptation into the same ecological niche as other organisms. That’s why they may have evolved similar (analogous) organs.
Remember, Bat's wing and horse's front foot are considered as homologous organs because they are similar in origin, but dissimilar or similar in function.

Therefore, the correct answer is option B.

Additional information:
Keep in mind, homology is defined as the similarity because of shared ancestry in between a pair of structures or genes in different taxa. We have common example of homologous structures- forelimbs of vertebrates, the front flippers of whales, the wings of bats and birds, the arms of primates, and the forelegs of four-legged vertebrates like dogs and crocodiles are all believed to be derived from the same ancestral tetrapod structure.

Note: Homology is the study of likeness or similarity between species that is resulted from inheritance of traits from a common ancestor. Remember, the study of similarities or homology is divided into three main categories- the structural, developmental, and molecular homology.