Amphibians is a class of animals grouped in the evolutionary scale between reptiles and fish and have 3 orders with 4400 species.
The three orders are
Caudata or tailed amphibians, which include salamanders and sirens.
Anura [
Salientia] or tailless amphibians which include frogs and toads.
Cymnophiona, which includes caecilians or wormlike amphibians.
Amphibians are believed to have been the first vertebrates which ventured out of water 400 million years ago to check out a new environment, dry land. Their golden age was the Carboniferous Era and their decline started already in the Mesozoic Era. Nowadays worldwide they are the class of animals with the fewest living species.
Amphibians like reptiles are cold-blooded animals but lack their protective scales, therefore they need always water for their skin to stay smooth and moist and so to be able to survive.
They lay jelly-like eggs in the water, which in most species develop into larvae. In the case of frogs and toads, those gill-breathing young are called tadpoles, which later metamorphose into air-breathing adults.
