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Definition: amphibian from Philip's Encyclopedia

Class of egg-laying vertebrates, whose larval stages (tadpoles) are usually spent in water but whose adult life is normally spent on land. Amphibians have smooth, moist skin and are cold-blooded. Larvae breathe through gills; adults usually have lungs. All adults are carnivorous but larvae are frequently herbivorous. There are three living orders: Urodela (newts and salamanders); Anura (frogs and toads) and Apoda or caecilians.


Summary Article: amphibian from The Hutchinson Unabridged Encyclopedia with Atlas and Weather Guide
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Image from: Amphibians have declined in number in recent... in Encyclopedia of Environment and Society

Member of the vertebrate class Amphibia, which generally spend their larval (tadpole) stage in fresh water, transferring to land at maturity (after metamorphosis) and generally returning to water to breed. Like fish and reptiles, they continue to grow throughout life, and cannot maintain a temperature greatly differing from that of their environment. The class contains about 4,500 known species, 4,000 of which are frogs and toads, 390 salamanders, and 160 caecilians (wormlike in appearance).

According to analysis of statistics from over 900 amphibian populations taken 1950–97, by Canadian and Swiss researchers, and published in 2000, amphibian populations have been declining at a rate of about 4% per year. US biologists concluded that the marked worldwide decline in amphibian populations is unlikely to have a single cause. Possible causes have been cited as increased ultraviolet radiation exposure, pollution, global climate change, and infection.

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