The Oxygen Cycle

The Oxygen Cycle explains how the oxygen used through respiration (in animals and humans) produces carbon dioxide and then once again becomes oxygen! If oxygen was just turned into carbon dioxide we'd eventually run out. (bad!) Plants rely on photosynthesis to survive and the process of photosynthesis takes carbon dioxide and produces oxygen with the addition of water and sunlight. This cycle repeats over and over and keeps our atmosphere full of oxygen! (21% oxygen, in fact)