They inhabit a wide variety of habitats, with most species living within terrestrial, fossorial, arboreal or freshwater aquatic ecosystems.
Thus amphibians typically start out as larvae living in water, but some species have developed behavioural adaptations to bypass this.
The list below largely follows Darrel Frost's Amphibian Species of the World (ASW), Version 5.5 (31 January 2011).
Another classification, which largely follows Frost, but deviates from it in part is the one of AmphibiaWeb, which is run by the California Academy of Sciences and several of universities.
The major differences between these two classifications are: There are a total of 8216 amphibian species in three orders.