Amphibians begin their lives in the water. As they mature, they develop lungs and live part of the time on land. Reptiles are found mostly on land. They are covered with scales, which help keep them from drying out. Birds have feathers, wings, and porous bones, that allow them to fly.
Mammals are also warm-blooded and are covered with hair or fur.
Most mammals give live birth to their young, nurse them with milk, and care for them.