Question

Opposable thumb is found in______ and it helps in
(a) Camel, walking
(b) Lizard, hibernation
(c) Monkey, grasping
(d) Kangaroo, Hopping

Answer 1

Hint: Evolution causes change in one form to another, resulting in a new generation different from the ancestor. Evolution in organisms occurs through natural selection which helps them in adaptation to changing environment, Opposable thumb means the position of the thumb will be opposite to that of fingers, it is also a type of evolution in certain vertebrates.

Complete Answer:
The opposable thumb is found in monkeys and it helps in grasping an object.
Humans and monkeys both belong to anthropoid apes that's why there are some similarities between human and monkey-like mobile shoulder joints, grasping hands, and continuous reproduction.
All primates show opposable thumbs which helps them in climbing, grasping, and other suspensory behavior. The evolution of a fully opposable thumb is to take place in Homo habilis which continued till the evolution of modern man.
In camel, both hind limb and forelimb are modified into long legs with broad elastic pad, in front of pad two hooves are present which is morphologically similar to toenail. This type of modification helps them to easily walk on sand.

Additional information: Different lizards show different numbers of digits in their hindlimb and forelimb which depend upon their adaptation toward the environment. Some lizards are quadruple, some are bipedal while some lizards are limbless. House lizards show 5 digits on both limbs with the presence of a suction pad which helps them to climb in the wall.
It is believed that kangaroos move on five legs while walking. Kangaroo also uses its tail with both hind limb and forelimb because the tail exerts more forward force than both the limbs. While hopping kangaroos only use their hind limbs. There are five digits present in both the limbs of the kangaroo, these digits are poorly developed with the absence of thumb, and $2^{nd}$ and $3^{rd}$ digits are joined with $4^{th}$ digits.
So, the correct answer is ‘(c) Monkey, grasping’.

Note: Spider monkey and colobus are thumbless whereas tarsals and marmosets have non-opposable thumbs, lemur, and squirrel monkey show pseudo-opposable thumb. These primates are the exception in case of limb modification.