Question

Complete the following table (Carefully study the carbon, oxygen and nitrogen cycles).

Bio-geo-chemical cycles	Biotic processes	Abiotic processes
1. Carbon cycle
2. Oxygen cycle
3. Nitrogen cycle

Answer 1

Bio-geo-chemical cycles	Biotic processes	Abiotic processes
1. Carbon cycle	Release of CO2 through respiration. Fixation of atmospheric Carbon dioxide through photosynthesis.	Release of CO2 in the atmosphere by burning of fossil fuels, wood etc.
2. Oxygen cycle	Release of O2 through photosynthesis and its consumption in processes like respiration etc.	Photo dissociation of water vapour in the upper atmosphere, as a result of which oxygen is released when water molecules are split by light. Evaporation of water at the surface of water bodies.
3. Nitrogen cycle	Nitrogen fixation, nitrification, ammonification.	Nitrogen fixation in atmosphere through lightning.