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Li fe f rom the Sun   The Sun , s heat and light   make Earth a comfortable   home for living things.

The Earth is unique among the planets because it teems with life. A huge variety of different kinds, or species, of plants and animals live on the land, in the oceans, and in the air. Life forms vary in size from microscopic mites to gigantic whales bigger than a house. Most forms of life on our planet need warmth, water, and oxygen. They need warmth so that life-processes can take place in their bodies. They need water to carry substances around their bodies. And they must breathe the oxygen in the atmosphere to stay alive.

Just right The Earth provides the warmth and water needed for life because it is in exactly the right position in the Solar System. If the Earth were closer to the Sun, all the water would evaporate and the temperature would be too high for living things. If the Earth were much further away from the Sun, it would be too cold for living things to thrive.

∆ One of the Earth ,s tiny creatures, the 0.07-in (2mm) head louse. Its favorite habitat is human hair.

Life protector The Sun sends not only heat and light to the Earth, but also dangerous rays, such as ultraviolet (UV) rays. A layer of gas called ozone in the atmosphere blocks most UV rays, but pollution has caused the ozone layer to thin. If it becomes too thin, it will let through UV rays that could harm living things.

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