Knowra Oxygen cycle Oxygen cycle The oxygen cycle is the movement of oxygen among the atmosphere, oceans, living organisms, and Earth’s crust through biological, geological, and chemical processes.
Photosynthesis : The process by which organisms use light energy to convert carbon dioxide and water into organic matter, releasing oxygen. Oxygenic photosynthesis is the major biological source of free oxygen in the atmosphere and oceans.
Atmosphere : The layer of gases surrounding a planet, held in place by gravity. Atmospheric oxygen is the cycle’s most familiar reservoir of free molecular oxygen.
Dissolved oxygen : The concentration of molecular oxygen dissolved in water. Its levels reveal whether aquatic oxygen supply keeps pace with biological consumption.
Aerobic respiration : Cellular energy production that uses oxygen as the final electron acceptor. The availability of free oxygen enables this high-yield form of metabolism.
Cellular respiration : The process by which cells extract energy from organic molecules, commonly using oxygen and releasing carbon dioxide and water. Aerobic respiration consumes oxygen produced by photosynthesis.
Hydrosphere : All water at or near Earth’s surface, including oceans, lakes, rivers, groundwater, and ice. The hydrosphere stores oxygen in dissolved form and in water molecules.
Eutrophication : The enrichment of water with nutrients that stimulates excessive growth of algae or aquatic plants. Decomposition of nutrient-fueled blooms can remove oxygen and create hypoxic waters.
Oxygen toxicity : Tissue damage caused by excessive exposure to oxygen or reactive oxygen compounds. Oxygen supports metabolism but can also generate damaging reactive molecules.
Oxidation : A chemical process in which a substance loses electrons, often through reaction with oxygen. Oxidation transfers oxygen into minerals and other compounds, removing it from free-oxygen reservoirs.
Biosphere : The parts of Earth where life exists, including organisms and the environments they inhabit. Living organisms take up, release, and incorporate oxygen throughout the cycle.
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