Frogs are small, tailless animals with bulging eyes. Almost all frogs also have long back legs. The strong hind legs enable them to leap distances far greater than the length of their body. Frogs live on every continent except Antarctica. But tropical regions have the greatest number of species. Frogs are classified as amphibians. Most amphibians, including rnost frogs, spend part of their life as a water animal and part as a land animal.

The first frogs appeared on earth about 180 million years ago. About 2600 species of frogs have developed from these early ancestors. Some species spend their entire life in or near water. Others live mainly on land and come to the water only to mate. Still other species never enter the water, not even to mate. Many kinds are climbers that dwell in trees. Others are burrowers that live underground.

Frogs, like all other amphibians, are cold-blooded, that is, their body temperature tends to be the same as the temperature of the surrounding air or water. Frogs that live in regions with cold winters hibernate. Some species hibernate in burrows. Others spend the winter buried in mud at the bottom of a pond or stream, breathing through their skin. During hibernation, a frog lives off materials stored in its body.

Adult frogs eat mainly insects and other small animals, including earthworms, minnows, and spiders. Most frogs use their sticky tongue to capture prey. The tongue is flipped out of the mouth in response to movement by the prey.

Most frogs have teeth only on their upper jaw. As a result, frogs swallow their prey in one piece. To aid in the swallowing process, the frog's eyes sink through openings in the skull and force the food down the throat.