The water cycle:
The movement of water between the oceans, atmospher, land, and living things is called the water cycle. During evaporation the suns heat causes water to change from liquid to vapor. In the process of condensation the water vapor cools and returns to a liquid state. The water that falls from the atmosphere to the land is precipitation.
The carbon cycle:
The exchange of carbon between the environment and living things is known as the carbon cycle. Photosynthesis is the basis of the carbon cycle. During photosynthesis plants use carbon dioxide from the air to make sugars. Most animals get carbon by eating plants. Then respiration breaks the sugar molecules down to release energy.
The nitrogen cycle:
The movement of nitrogen between the environment and living things is called the nitrogen cycle. Bacteria in the soil are able to change nitrogen gas into forms that plants can use. This process is called nitrogen fixation. Other organisms may then get the nitrogen they need by eating plants or organisms that eat plants.