Answer:
Biogeochemical cycles
Biotic processes Abiotic processes
Carbon Cycle Release of oxygen and CO
2
through photosynthesis and respiration respectively. Release of CO
2
in the atmosphere by burning of fossil fuels, wood, etc.
Oxygen Cycle Release of O
2
through photosynthesis and its consumption in processes like respiration etc. Photodissociation of water vapour in the upper atmosphere, as a result of which oxygen is released when water molecules are split by light
Nitrogen Cycle Nitrogen fixation, nitrification, ammonification Nitrogen fixation in atmosphere and denitrification