Amphibians are a class of vertebrates that include frogs, toads, salamanders, newts and caecilians. All amphibians are cold-blooded, and most lay eggs. The majority of species undergo metamorphosis, moving from a larval stage (usually aquatic) through the development of limbs and lungs to become terrestrial adults. However, a significant minority of the species develop directly from eggs, usually laid on land, without a larval stage. There are also a few viviparous species that give birth to young, without laying eggs.
Almost all species are dependent on moist conditions, and many require freshwater habitats in which to breed. The greatest diversity occurs in tropical forests, with species richness generally lower in temperate and arid regions. Amphibians are entirely absent from marine environments.
Amphibians are excellent indicators of the quality of the overall environment, as they are very sensitive to perturbations in ecosystems. Additional general information about amphibians can be found on AmphibiaWeb.