Oxygen cycles through Earth’s environment in several forms. It can be dissolved in the air or in water. Plants and animals breathe oxygen and return it to the air and water as carbon dioxide. Through photosynthesis, plans convert carbon dioxide and water into carbohydrates, and oxygen is released. The algae in the oceans and other water bodies replace about 90 percent of all oxygen used on our planet.
How is oxygen being used in the diagram?
credit: Amy Todd