| A | B |
|---|
| carbon dioxide-oxygen cycle | The movement of carbon dioxide and oxygen through an ecosystem |
| condensation | The process in which water vapor turns back into liquid when the air cools (how clouds form) |
| evaporation | The process by which water changes from a liquid to a gas |
| fixed nitrogen | Nitrogen combined with other elements to form a compound (the only form that can be used by most organisms) |
| ground water | Water from precipitation that travels through the ground |
| nitrogen cycle | The movement of nitrogen through an ecosystem |
| precipitation | The process in which water falls from clouds in the form of rain, snow, hail, or sleet |
| respiration | The process of breathing and turning oxygen into carbon dioxide; also, the process by which food, usually sugar, is broken down and energy is released |
| runoff | Water from precipitation that travels along the surface of the ground |
| water cycle | The movement of water through an ecosystem |
