The Nitrogen Cycle

1. Grace, Moose, and Kelsey The Nitrogen Cycle

2. Nitrogen Fixation by Bacteria on Plant Roots, Lightning, or the Haber Process • N2 gas in the atmosphere is not available for use by most organisms • Bacteria transforms it into ammonia through the process of nitrogen fixation so that plants can use it. • Bacteria either form symbiotic relationships with other organisms or live freely • Lightning also causes the oxidation of nitrogen in the atmosphere which is absorbed by the soil. • The Haber process is an industrial process used to make fertilizers in which nitrogen and hydrogen gases are combined under pressure with the use of a catalyst to form ammonia.

3. Feeding => Digestion or Egestion • Nitrogen absorbed by plants is ingested by herbivores and omnivores and is then either absorbed for use by the body and eventually recycled as waste or immediately ejected by the body and reabsorbed into the soil.

4. Nitrification • This process takes the ammonia from Nitrogen Fixation and transforms it into nitrites and nitrates which are then absorbed by plant roots • Preformed by nitrifying bacteria • Nitrosomonas convert ammonia to nitrites • Nitrobacteria convert nitrites to nitrates

5. Denitrification • Breaks down dead organisms and waste into ammonium ions, nitrite ions and nitrate ions to be taken up and recycled by plants. • Process preformed by denitrifying bacteria, some animals (insects, worms, ect.) and fungi.

6. Assimilation • Once taken in, nitrogen can be used to build more complex molecules or it can be assimilated into the system. • Nitrogen is used to build: • Amino acids and proteins • Nucleotides (the building blocks of DNA)

7. Works Cited: • http://www.biology.ed.ac.uk/research/groups/jdeacon/microbes/nitrogen.htm • http://nitrification.org/ • http://www.umich.edu/~lehnert/denitrification.html • http://dictionary.reference.com/browse/assimilation