Designs for Living
Mammals are among the most successful animals ever to have lived. Because they are warm-blooded, they can survive in almost any environment. To take advantage of different environments,, mammals have evolved different body shapes. They have adapted to life in the jungles, deserts and high mountains; in the polar regions; in the air and in the trees; beneath the ground and in the oceans. They have also adapted as they moved from one environment to another. The ancestors of today's horses, for example, lived in forests and were small enough to move among trees and undergrowth. When they began to live on the open plains. however, they grew larger and stronger so they could migrate in search of fresh food, and faster so they could escape the fast-moving predators of the plains. Looking alike Some mammals look similar and live in similar ways even though they are not related to each other and live in different parts of the world. Scientists call this "Convergent evolution...