- OXYGEN CYCLE:
Oxygen gas (O2) makes up about 1/5 of the Atmosphere.
Animals and other organisms use oxygen in Respiration. The oxygen is combined into many organic compounds.
Respiration ultimately releases oxygen back to the atmosphere in the form of Carbon dioxide (CO2). Decomposition of dead bodies releases additional CO2.
Plant photosynthesis uses the carbon dioxide and releases oxygen (O2) back to the atmosphere.
Some oxygen is also incorporated into soil, sediments, and rocks. This oxygen may be released by weathering and by the action of organisms.
- CARBON CYCLE:
Carbon dioxide (CO2) is present in the Atmosphere.
Plant photosynthesis "fixes" the carbon dioxide, converting the carbon into various organic compounds.
Animals that eat plants use these organic compounds and make new organic (carbon-containing) compounds.
Animals and plants all undergo respiration, a process that releases CO2 back to the Atmosphere.
The decomposition of dead animals and plants releases additional (CO2) back to the Atmosphere.
Some CO2 dissolves in water, and is used by aquatic animals, plants, and algae.
Some aquatic organisms use the CO2 to build shells made of calcium carbonate, CaCO3.
The accumulation of dead shells may become incorporated into sediments as carbonate minerals.
Carbonate minerals may be incorporates into sediments and into rocks such as limestone.
The weathering of these materials releases the CO2 back to the Atmosphere.
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