Amphibians
(Class: Amphibia)
Amphibians were the first vertebrates to colonise the land, over 370 mya (million years ago), and most members still require water for the larval stage of their life cycle. The group includes the salamanders, frogs, toads and caecilians, all of which have a 3 chambered heart. Many members absorb oxygen through their skin (mainly in the adult stage), which is kept moist with mucous secretions. They are all ectothermic, regulating their body temperature using outside sources.
