The various characteristics of animals that enable them to obtain food and shelter, to reproduce, and to protect themselves from predators are called adaptations. In a broad sense, all the characteristics of an organism are adaptations that have evolved through many generations to adapt, or fit, the organism for life in its normal environment.

Primates (such animals as humans, apes, monkeys, and lemurs) are among the many kinds of animals whose bodies are adapted to climbing trees. All primates have hands that are prehensile (fitted for grasping), and some have prehensile tails as well.

Animals' bodies are also adapted to obtaining and eating certain kinds of food. Carnivorous (flesh-eating) animals that catch large prey have strong, sharp teeth for tearing flesh. Some herbivorous (plant-eating) animals that feed on tough, bulky vegetation have broad-surfaced molars fitted for grinding. Their intestines are longer than those of carnivorous animals, and are adapted to breaking down plant fibers during digestion. A few animals, including humans and bears, are omnivorous, having bodies fitted for eating both animal and plant materials.

The bodies of animals are also adapted to protect them from their natural predators. Deer and gazelles have long legs and strong leg muscles to help them run away. Bears and cats have teeth and claws suited for defense as well as for attack. Skunks have glands that emit foul-smelling liquids to repel attackers. The hard shells of turtles and spiny coverings of porcupines are protective. The colors, markings, and shapes of many animals are helpful in concealing them from their predators.

The behavior of animals is also adaptive. The walking stick, an insect shaped like a stick or twig, positions its body in such a way on trees and shrubs that it resembles a twig even more, making it more difficult for predators to see it. A tree finch of the Galapagos Islands breaks off a cactus spine and holds it in its beak to dig out insects from tree bark. Similarly, chimpanzees use twigs to probe holes in wood or termite nests to get the insects out.