The oxygen cycle and carbon cycle are closely linked ecological processes that involve the movement of oxygen and carbon through the Earth's environment. They are fundamentally connected through photosynthesis and respiration:
- Photosynthesis in plants, cyanobacteria, and some protists captures carbon dioxide (CO2) from the atmosphere and, using sunlight, converts it into sugars while releasing oxygen (O2) as a byproduct. This process drives the flow of oxygen into the atmosphere and stores carbon in organic compounds.
- Respiration by animals, plants, and other organisms consumes oxygen to break down sugars, releasing energy, carbon dioxide, and water. This returns carbon dioxide to the atmosphere, completing the cycle.
Thus, the oxygen cycle is coupled to the carbon cycle because oxygen is produced during photosynthesis as carbon dioxide is fixed, and oxygen is consumed when organic carbon is oxidized back to carbon dioxide during respiration. Additionally, other processes like decomposition, combustion, and oceanic exchange are integrated in the cycles, regulating the balance of atmospheric gases critical for life and climate stability. For example, oceans absorb CO2 and release oxygen in complex interactions, and fossil fuel burning releases CO2 while consuming oxygen. In summary, the two cycles are interdependent: the carbon cycle involves cycling carbon between CO2 and organic carbon, while the oxygen cycle involves the cycling of oxygen gas, with photosynthesis and respiration serving as the biochemical linkages between them, maintaining ecological and atmospheric homeostasis.