Characteristics of Class Amphibian are given below:
1) The representatives of class Amphibia thrive well both on land and in water i.e. amphibious.
2) Amphibians are cold-blooded or exothermic animals. Unlike warm-blooded animals, which regulate their body temperature internally, amphibians derive heat from outside their body.
3) The skin is smooth, thin, hairless, porous and rarely scaled. The skin contains both mucus glands and poison glands.
4) A bone endoskeleton with varying numbers of vertebrae; ribs present in some, absent or fused to vertebrae in others.
5) A smooth, thin, porous skin containing both mucus glands and poison glands.
6) Four limbs which may vary in size with the forelimbs of some being much smaller than the hind limbs; some are legless.
7) Limbs have varying numbers of digits and webbed feet are often present; no true nails or claws.
8) The mouth is usually large with small teeth in upper or both jaws; two nostrils open into the anterior part of the mouth cavity.
9) Respiration is accomplished either separately or in combination by lungs, skin, and gills; some larval types possess external gills and these may persist throughout life.
10) A three-chambered heart consisting of two atria and one ventricle.
11) Body temperature regulation is exothermic in nature. That is, the body is heated from without rather than from within.
12) Separate sexes with internal fertilization via spermatophore a sperm packet on a stalk in salamanders and caecilians, but external fertilization in frogs and toads.
13) Ten pairs of cranial nerve are present.
14) Amphibians are the only vertebrates to undergo complete metamorphosis.
15) Eggs are usually laid in water or in a moist environment and fertilized externally. They change from an aquatic larval stage to a terrestrial form on reaching adulthood.
16) Larvae develop in water or very moist environments and undergo completemetamorphosis.