Chordates are members of the phylum Chordata. A chordate is an animal that has, for at least some part of its life a dorsal, hollow nerve cord; a notochord; pharyngeal pouches; and a tail that extends beyond the anus.
An amphibian is a vertebrates that, with some exceptions, lives in water as a larva and on land as an adult, breathes with lungs as an adult, has moist skin that contains mucous glands, and lacks scales and claws
Early amphibians evolved several adaptations that helped them live at least part of their lives out of water. Bones and limbs and limb girdles of amphibians became stronger, permitting more efficient movements. Lungs and breathing tubes enabled amphibians to breathe air. The sternum, or breastbone, formed a bony shield to support and protect internal organs especially the lungs.
First amphibian, Eogyrinus, is thought to have been about 5 meters long
Circulatory system is known as two loops. First loop carries oxygen- poor blood from the heart to the lungs and skin, and takes oxygen- rich blood from the lungs and skin back to the heart. The second loop transports oxygen rich blood from the heart to the rest of the body and then carries oxygen- poor blood from the body back to the heart.
Amphibians use kidney to filter wastes from the blood-urine
Amphibians eggs do not have shells but do dry out if not kept moist. When two amphibians reproduce the male jumps on the females back and squeezes. This makes the female release up to 200 eggs that the male then fertilizes.