Vertebrates are animals that have backbones that surround their nerve cords. The nerve cord is found along the back of an animal. The bodies of most vertebrates have a head and a trunk. They are called ectotherms or cold-blooded. That means that amphibians do not hold their body temperature constant like mammals, but their body temperature depends upon that of the surrounding environment.
Amphibians have soft, generally moist skin without scales.
Amphibians go through a two-stage life cycle. The are laid in water or a damp environment to keep from drying out. They experience a metamorphosis or change. When an amphibian hatches, it is in a gilled larval form. In frogs and toads this larva is called a tadpole .