Millions of years ago, a group of fish began to breathe both in and out of the water. Later they began to develop legs. These animals became amphibians, the ancestors of all reptiles, birds, and mammals. They first ventured out on land some 370 million years ago.
The word “amphibian” comes from the Greek words amphi, which means “both,” and bios, which means “life.” Amphibians are cold-blooded vertebrates that live both in freshwater and on land. Their body temperature generally matches the temperature around them and to warm up, amphibians often bask in the sun.
There are three main groups of amphibians. The largest group includes the true frogs, tree frogs, and toads. The second group is the salamanders. The third group is the caecilians, wormlike creatures.