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Amphibians

What Is an Amphibian?

Amphibians lead double lives—one in water and one on land. Many begin life with gills, then develop lungs as they age. They are vertebrate animals that include frogs, toads, salamanders, and newts as well as odd, wormlike caecilians (seh-SILL-yuns). They are cold-blooded, using the environment to regulate their body temperature. Early amphibians were the first animals to leave the sea and venture onto land, forming a crucial link from fish to terrestrial reptiles.