They reproduce externally in the water. Amphibians undergo metamorphosis, or changes from the egg to an adult. They have a three chambered heart, brain, dorsal hollow nerve cord, eyes and a tympanic membrane. Frogs and toads have no tails and are in class anura . Salamanders and newts are in class caudata .
Caecilians are limbless and have a short tail, or none at all.
Class reptilia includes the lizards, snakes, turtles, alligators, and crocodiles. Reptiles have dry and thick skin to protect them from drying out, as well as claws made from modified skin. Except for crocodiles, which have a four chambered heart, reptiles have a tree chambered heart. They have well developed kidneys and lungs, and excrete uric acid. They have a full digestive system and have an internal bone structure.