Amphibians are the earliest tetrapods. They were descended from fish like ancestors. They were developed in the Devonian period. They flourished during carboniferous period. It is called “Age of Amphibians”.
Amphibians can lead their life on land and in water. They are cold blooded vertebrates. They show four pent dactyl limbs. They are supported by pectoral and pelvic girdles.
Their skin is soft. It is glandular. They do not how exoskeleton. They perform respiration by lungs and skin. In some amphibians gills are also seen. They show three chambered head. Their R.B.C. are nucleated. Sexes are separate.
In the present day world nearly 15000 species are living. They belong to only three order
1) Anura 2) Urodela 3) Apoda