Question

Explain why the amniotic egg is an important evolutionary breakthrough. Name three classes of animals that are classified as “Amniotes”.

Answer 1

Ans- Amniotic egg is covered by tough outer shell which protects it from the outside environment. Inside the shell are four sacs from which first sac, the chorion, carries oxygen from the shell to embryo and carbon dioxide from embryo to the shell. Within this is amnion which prevents it from drying out and third shell, stores wastes and forth sac yolk sac holds and digests nutritious yolk for embryo.

Amniotic egg is an important evolutionary breakthrough because it allows incubation of egg in terrestrial environment. It allowed the first reptiles to colonize land more than 300 million years ago. Reptiles can lay eggs on terrestrial environment due to amniotic egg while fishes aand amphibians had to lay eggs on the other hand in water because they are not protected in environment.

The three classes of animals that are classified as amniotes are-

1. Class reptilia (reptiles)

2. Class aves (birds)

3. Class mammalia (mammals)