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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.
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