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How animals live

The giant panda has adapted its diet to bambooThe giant panda has adapted its diet to bamboo The process of evolution ensures that only living things that are suited, or adapted, to their environment will survive. An animal or plant that is poorly adapted to its surroundings soon loses out in the struggle for survival. Animals are adapted to three major features of their environment: the climate (including temperature and rainfall), the food sources available and the predators. The key features of an animal are that it has a body made of many microscopic cells and it gets its energy and nutrients by eating—that is, it takes in or consumes food. Animals can also move about for at least a part of their lives.

A sponge, a simple marine animalA sponge, a simple marine animal
A member of a new group of insects, discovered in 2001A member of a new group of insects, discovered in 2001

Number of species

Scientists have identified at least 2 million different kinds or species of animal, from tiny worms smaller than a comma, to huge elephants and blue whales. There are almost certainly at least the same number of species still to be identified—for example, insects and other small invertebrates in tropical forests yet to be discovered. The total number of animal species may be far higher: 10 million, or even more.

To protect their almost hairless bodies from the hot African sun (when not submerged in water), hippos have a substance in their skins that forms a sunscreen. It also prevents the growth of disease-causing bacteria.

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