Oxygen cycle

 The oxygen cycle is a biogeochemical cycle that describes the movement of oxygen (O2) within and between the Earth's atmosphere, biosphere, and lithosphere. This is a critical process that supports the survival of many organisms, including humans.

The oxygen cycle begins with photosynthesis, in which green plants, algae, and some bacteria use sunlight, carbon dioxide (CO2), and water (H2O) to produce oxygen and organic compounds. This process releases oxygen into the atmosphere, which is used by living organisms during respiration.
During respiration, organisms take in oxygen and use it to release energy from organic compounds, producing carbon dioxide and water as waste products. This process uses up oxygen and releases carbon dioxide into the atmosphere.

The oxygen cycle is also affected by other processes such as combustion and decomposition. Combustion, the burning of organic matter, consumes oxygen and releases carbon dioxide into the atmosphere. During decomposition, that is, decomposition of dead organic matter, carbon dioxide is released and oxygen is consumed.
Overall, the oxygen cycle contributes to maintaining the gas balance in the Earth's atmosphere and is essential for the survival of many organisms.