Question

why birds are called amniote?

Answer 1

Hey friend, Harish here.

Here is your answer:

All birds lay amniotic eggs. Hence they are know as amniote.

→ These amniotic eggs have tough outer covering to protect the eggs from outer harmful environment.

→ Not only Birds , but few other reptiles and also mammals which lays amniotic eggs are known as amniote.
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Hope my answer is helpful to you. 

Answer 2

Answer:

All birds are aminiotic because, if we check the eggs laid by the birds, we will be able to notice an amnion layer beneath the shell, which decreases the vulnerability of the young one inside the egg from predators.