Question

describe nitrogen and carbon cycle

Answer 1

Nitrogen Cycle

the series of processes by which nitrogen and its compounds are interconverted in the environment and in living organisms, including nitrogen fixation and decomposition.

Carbon Cycle

The carbon cycle is the biogeochemical cycle by which carbon is exchanged among the biosphere, pedosphere, geosphere, hydrosphere, and atmosphere of the Earth. 

Answer 2

The cycling of chemicals between the biological and the geological world is called biogeochemical cycle.The biotic and abiotic components of the biosphere constantly interact through biogeochemical cycles. During these interactions, there is a transfer of nutrients between living organisms and the non-living environment.The four important biogeochemical cycles are water cycle, nitrogen cycle, carbon cycle and oxygen cycle.

Carbon cycle maintains the balance of the element carbon in the atmosphere. Carbon is found in various forms on the Earth. 
*Diamond and graphite found in the soil are made up of an element called carbon. 
*Carbon is present in the atmosphere as carbon dioxide. 
*Carbon can also occur as carbonates and bicarbonate salts in minerals. The endoskeletons and exoskeletons of various aquatic animals are also formed from carbonate salts.
*Carbon is an essential part of nutrients like carbohydrates, fats, proteins, nucleic acids and vitamins.
Carbon cycle maintains the amount of carbon in the atmosphere. The carbon cycle starts in plants. 
Step - 1
Plants, use carbon dioxide in the atmosphere, convert it into glucose in the presence of sunlight by the process of photosynthesis. Plants and animals break these carbohydrates for energy and release carbon dioxide through respiration.
Step - 2
When the plants and animals die, fungi and bacteria decompose the dead remains.  This releases the carbon in the remains as carbon dioxide. 
Step - 3
Some plants and animals which get burried in the soil under certain temperature and pressure over millions of years get transformed into fossil fuels. Coal and petroleum are some of the fossil fuels. On burning these fuels, carbon dioxide is released into the atmosphere.
Carbon is thus cycled repeatedly through different forms by the various physical and biological activities. 

Nitrogen cycle
Nitrogen gas makes up around 78% of our atmosphere. It forms a part of many molecules like proteins, nucleic acid and some vitamins. Nitrogen is also found in other biologically important compounds such as alkaloids and urea. Nitrogen is thus an essential nutrient for all life forms.
The sequence in which nitrogen in the atmosphere is passed into the soil and life forms, and then released back into the atmosphere, is called the nitrogen cycle.

a) Nitrogen is introduced to the soil by fertilizers or animal and plant residues. Bacteria in the soil convert the nitrogen to ammonium and nitrate, which is taken up by the plants by a process of nitrogen fixation.
b) Ammonification: The process of the production of ammonia from organic compounds is called ammonification.  Ammonification is the process — carried out by a variety of microorganisms — that breaks down proteins, amino acids, and other nitrogen-containing compounds in dead and waste organic matter to form ammonia.
c) Nitrification: It is the process by which ammonia is converted to nitrites (NO2-) and then to nitrates (NO3-).   This process naturally occurs in the environment, where it is carried out by specialized bacteria.
d) Denitrification: It is the biological conversion of nitrate to nitrogen gas, nitric oxide or nitrous oxide.   These compounds are gaseous compounds and are not readily available for microbial growth; therefore they are typically released to the atmosphere.   Nitrogen gas makes up over 78% of atmospheric gases, thus the release of N2 to the atmosphere is benign.  
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