Animals of the World

Animals are organized into groups that share key traits, which helps reveal how different species are related. Primates form one such group of mammals, including monkeys, apes, and humans, generally marked by grasping hands, forward-facing eyes, and relatively large brains. Many primates are social and live in groups, and several, such as the great apes, are intelligent animals capable of complex behavior.

Reptiles are another major group, cold-blooded animals with scaly skin that includes snakes, lizards, turtles, and crocodiles. Large snakes such as pythons are constrictors that coil around prey and squeeze rather than using venom. Birds, by contrast, are warm-blooded and feathered; while most fly, some such as penguins are flightless and have instead become strong swimmers adapted to cold seas.

The animal kingdom also includes amphibians, fish, and the vast number of invertebrates such as insects and arachnids. Each group has adaptations suited to its environment, and the relationships among predators, prey, and competitors shape the ecosystems they share. Many animals today are threatened by habitat loss, and conservation efforts work to protect rare and endangered species. Classifying animals into these groups helps biologists understand how species are related and how the traits they share have arisen over time.

Frequently asked questions

What makes an animal a primate?

Primates are mammals that typically have grasping hands, forward-facing eyes for depth perception, and relatively large brains. The group includes monkeys, apes, and humans.

How do pythons catch their prey?

Pythons are constrictors. They coil around prey and tighten their grip until the animal can be swallowed, rather than using venom.

Why can't penguins fly?

Penguins are flightless birds whose wings have become flippers adapted for swimming. They are powerful swimmers rather than fliers.