Question

Snakes do not have legs because
A) Legs are lost during their entry in tunnels
B) Legs are lost during evolution
C) The ancestors of reptiles did not have legs
D) There are no legs in lizards.

Answer 1

Hint:Snakes are limbless reptiles that travel through winding motions which are very different from the contraction process of earthworms and related organisms. However, it is highly possible that ancestral snakes did have legs.

Complete answer:
If snakes were to lose their legs on entry into tunnels, they would all be born with a complete set of limbs. This, however, is not the case. Option A is clearly incorrect.

In prehistoric times, fossil skeletons show that snakes used to have very tiny legs like other reptiles. However, with evolution and the mutation of certain genes, these animals lost their limbs, acquiring other evolutionary characteristics. Examination of the skeleton of many snake species like pythons shows the presence of vestigial limbs relating back to the front and back legs they had about 150 million years in the past. The absence of limbs is connected to one particular gene, the Sonic Hedgehog gene. Option B is the correct answer.

The ancestors of modern day reptiles include the dinosaurs. Dinosaurs are known to have well developed fore and hind limbs. Crocodiles are also considered modern day dinosaurs, as are birds. Option C is incorrect.

If we look around us at the gecko, the garden lizards, crocodilians, and so on, we can clearly see that they have limbs. Option D is incorrect and unrelated.

Hence the correct answer is option ‘B’.

Note:The sonic hedgehog gene remains switched off in snakes, and on in other members of the lizard family. Sometimes this gene switches on in pythons later in development, and they may have very tiny limbs. It is possible with the right stimulus the sonic hedgehog gene can be switched on in snakes, so that they again grow limbs. Evolution has provided for both options.