what is an amphibian

An amphibian is a vertebrate animal with a backbone. They are cold-blooded, which means their body temperature changes with their environment. Amphibians are small animals that need water or a moist environment to survive. They can breathe and absorb water through their very thin skin. Amphibians also have special skin glands that produce useful proteins. Some transport water, oxygen, and carbon dioxide either into or out of the animal. Others fight bacteria or fungal infections. Amphibians lay jelly-covered eggs, called spawn, usually in still, fresh water, often among water plants. The resulting young, known as tadpoles, are aquatic and have feathery, external gills, but soon develop lungs and legs and leave the water. Adult amphibians spend most of their life on land, usually in damp habitats, only returning to the water to breed in the spring. The three groups of amphibians in the world today are the frogs and toads, the newts and salamanders, and the caecilians (legless burrowing types) .