Amphibians

Amphibians (class Amphibia), such as frogs, toads, salamanders, newts, and gymnophiona, are cold-blooded animals that metamorphose from a juvenile, water-breathing form to an adult, air-breathing form. Typically, amphibians have four limbs. Unlike other land animals, amphibians lay eggs in water, as their fish ancestors did. Amphibians are superficially similar to reptiles.

In recent decades, there has been a dramatic decline in amphibian populations around the globe and many species are now threatened or extinct. Scientists do not agree on the cause, but it is widely believed to be a direct result of the amount of water pollution made from industrial factories and other similar sources.

The most obvious part of the amphibian metamorphosis is the formation of four legs in order to support the body on land. But there are several other changes:

• The gills are replaced by other respiratory organs, i.e., lungs.
• The skin changes and develops glands to avoid dehydration.
• The eyes develop eyelids and adapt to vision outside the water.
• An eardrum is developed to lock the middle ear.
• In frogs and toads, the tail disappears.

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