The word amphibian means double life. That is because an amphibian may start its life looking like fish. This baby is called a tadpole. A tadpole has gills and lives in fresh water. As a tadpole grows, it may lose its gills. It grows lungs and four legs. Then an amphibian comes out of the water and lives on land.

There are three groups of amphibians: frogs and toads, salamanders and newts, and legless amphibians. These amphibians have a lot in common. They absorb water and air through their skin. They are cold-blooded. That means that their body temperature is about the same as the air or water around them.

Amphibians are different in many ways, too. Some have smooth, slimy skin like frogs. Others have drier, bumpy skin like toads. Some look like tadpoles their whole lives. Others have no legs and look like snakes or worms.

Amphibian eggs do not have hard shells. They are protected by a jelly-like coating. The eggs need moisture to survive. That is why many amphibians lay their eggs in water. Other amphibians keep the eggs inside their bodies and give birth to live young. Still others lay their eggs in damp places on land. The tadpoles go through their changes inside the eggs.

There are thousands of kinds of amphibians. They live almost everywhere. Amphibians have been around for about 360 million years. Now they are in danger. Things like pollution, loss of habitat, and climate change threaten them. Invasive species and disease harm them, too.