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Teja Veeration 31 October 2012
Transcript of Biogeochemical Cycle
Period-5 Nitrogen Cycle Background 78% of our atmosphere is gaseous nitrogen, N2. But this inert form of nitrogen cannot be used by many organisms. Therefore, it must be "fixed" to be used by plants. Animals in turn receive their nitrogen by eating plants or animals that have fed on plants. After using the nitrogen, it is released back into the atmosphere. This is the basis of the nitrogen cycle. Nitrogen Fixation Nitrogen can be fixed in 2 methods:
1. Atmospheric fixation by lightning, forest fires, and even lava flow
2. Biological fixation by nitrogen-fixing bacteria in legumes
These 2 methods fix N2 by combining it with hydrogen to make NH3. Some of it is also converted NH4+. Nitrification NH3 and NH4+ is converted to nitrite (NO2-) or nitrate (NO3-) through nitrifying bacteria. This form of nitrogen is then assimilated by the roots of a plant to be used in its various biological processes. Ammonification After using nitrogen, plants and animals produce waste which is converted back into NH3 and NH4+ by decomposers such as bacteria and fungi. Denitrification NH3 and NH4+ is converted back into nitrite or nitrate and then released into its gaseous form, N2. This process occurs under strict anaerobic conditions by bacteria. Biotic And Abiotic Impacts Biotic-Nitrogen is used by living organisms to produce amino acids, proteins, and nucleic acids.
Biotic-It is necessary for the function of chlorophyll (which is used in photosynthesis) and enzymes.
Abiotic- Denitrification results in the increase in N2 in the air which destroys the ozone layer, increases environmental pollution, and contributes to global warming. Video on the Human Impact on the Nitrogen Cycle Acid rain, algal blooms, and eutrophication are some of the effects of human interaction with the nitrogen cycle. Most of these effects are caused by fossil fuel burning, fertilizer runoff, or other human actions that deposit large amounts of nitrogen in the environment.