plants

Photosynthesis is the cycle of oxygen and carbon-dioxide and it goes like this:

1. First we breath oxygen and let out carbon-dioxide
2. A plant(S) breath in the carbon dioxide to create there sugar
3. Then they let out oxygen which we breath as before

and that is the basic photosynthesis. Also a very big part of the nitrogen cycle. The nitrogen cycle starts when a plant dies. When a plant dies nitrogen is let off of the plant, other plants absorb it or it goes to the underwater plants.