Question

An ape having ischial callosities is
A. Gibbon
B. Orang-utan
C. Gorilla
D. Chimpanzee

Answer 1

Hint: These are present in animal's buttocks to provide them support when they sleep on the thin branches of a tree in the straight upright position beyond the reach of predators.

Complete answer:
First of all, what is ischial callosities. These occur in animal's buttocks. It forms the lower and the back part of hip hop. In simple words, when the calloused structures are found in the buttock region then these are called as ischial callosities. This helps the monkey to sleep in a sitting position on the thin branches without falling and even beyond the reach of predators hence, this is a really important part. These are found in gibbons.

> First option is gibbon. Gibbons are small and primitive apes and these are found in Assam hills. It is a correct one as there is presence of ischial callosities seen in the gibbons.

> Second option is Orang-utan, these are natives to Indonesia and Malaysia. These do not have ischial callosities and they do not require it. This option is hence incorrect.

> Option C is Gorilla which are ground dwelling herbivorous apes and these are found in the forest of Sub-Saharan Africa. These also do not have callosities and therefore this option is incorrect.

> The last option is Chimpanzee, these are natives of Savannah of tropical Africa. These do not have callosities too so this option is also not the right one.

Hence, The correct answer is option (A).

Additional information:
Ischial callosities are the adaptations which are developed for the comfort sitting position on thin branches. New world monkeys have also developed as mechanisms for the exploitation of food resources which are found on the terminal branches. Some of them are in process of losing their ischial callosities because of their large body, for example, Pongids. Small monkeys do not possess any of these adaptations because of their body size as they can efficiently exploit smalls or large branches for food.

Note: These callosities are generally found in gibbons and they are required for the straight upright sitting position while they sleep in order to sleep on these branches. Some of them do not have these adaptations as from the given option only gibbons have these adaptations. Small monkeys even do not require it and large monkeys lose it because of their body size.