Tuesday, April 3, 2012

Amphibians

The amphibians were the first back boned animals to make a go of life on land, but even then they had to return to the water to breed- just like most of today’s amphibians. They evolved from a group of air breathing fish whose fins became transformed into legs capable of supporting their bodies. With length of 4 meter and more, some of these early amphibians were very much larger than their present day descendants. Amphibians feed mainly on insects and other invertebrates, although the larger species also eat small vertebrates. Most frogs and toads catch their prey with a long sticky tongue, which is flicked out at high speed. The lungs are not very efficient and much of the animal’s oxygen is obtained through the thin skin, which is well supplied with blood vessels. The thin skin restricts the amphibians ot damp habitats.

The Amphibians are divided into numerous orders, but only three of these have living members. The gymnophiona contains the worm like caecilians of tropical areas. The Urodela contains the tailed amphibians the newts and the rather more terrestrial salamanders. The Anura contains the frogs and toads, which are tailless and mostly adapted for jumping. In Europe, the name frog is applied to amphibians with smooth skins, while toad is applied to those with warty, often drier skins. This distinction, however, is not always made elsewhere in the world.