The Oxygen - Carbon Dioxide Cycle

Most living things on Earth must have oxygen to live. Oxygen is part of the air we breathe. About one fifth of our air is oxygen. Where does oxygen come from?


Plants make oxygen. Plants collect energy from the sun. They use it to make their own food, called sugar.


Plants need carbon dioxide. It is also part of the air. Plants use carbon dioxide to make their food. When they make food, they give off oxygen. To them, oxygen is a waste product. To us, oxygen is life!


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