Plants trap energy^* from the sun in a process called photosynthesis. As long as there is sunlight and carbon dioxide available, plants will take in carbon dioxide and water. They will use these materials to make food.

But this energy is no good to them until they use it. The process of using food and oxygen to get energy is called respiration.

Plants must use the energy they trap in the food to stay alive. That's where respiration comes in. At night, plants take in oxygen and use it to get energy from the food they stored. This is a chemical reaction. This is the same reaction that takes place in animals that eat the plants.

Fortunately for us, the plants make much more food than they use so that there is plenty left over for animals to eat. (28.8)(56.7) (Download)