The oxygen cycle<span> is the biogeochemical </span>cycle<span> of</span>oxygen<span> within its three main reservoirs: the atmosphere (air), the total content of biological matter within the biosphere (the global sum of all ecosystems), and the Earth's crust.</span>
The process by which oxygenreleased into the atmosphere by photosynthetic organisms is taken up by aerobic organisms while the carbon dioxide released as a by-product of repiration is taken up for photosynthesis. Origin ofoxygen cycle Expand.
