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The Nitrogen Cycle 318-1 illustrate the cycling of matter through biotic and abiotic components of an ecosystem by tracking carbon, nitrogen and oxygen What is Nitrogen? • After carbon, oxygen, and hydrogen, nitrogen is the most common element found in living organisms. • It is an essential part of proteins, DNA, and other compounds. • One of the main ingredients in fertilizer is nitrogen. Nitrogen Cycle • Like carbon, nitrogen passes along food chains and circulates between biotic and abiotic parts of the environment. Nitrogen Fixation • Earth’s atmosphere is nearly 80% nitrogen gas, but many organisms cannot absorb nitrogen directly from the air. • In order to be used, nitrogen atoms must first be fixed (pulled from the air and bonded to other elements to make new compounds). This process is called nitrogen fixation. • In nature, nitrogen fixation is carried out by a few species of nitrogen-fixing bacteria that live in soil or water. Example • Nitrogen can combine with hydrogen to make : NH4+ • Nitrogen can combine with oxygen to make : NO3• Plants can then absorb these compounds through their roots and use the nitrogen. Animals can get nitrogen by eating plants and other animals. • After nitrogen from the atmosphere has been fixed, it enters the soil and water. There it is available for living organisms to use. • The nitrogen compounds that enter plants, move through food chains and return to the soil and water through dead organisms and waste materials. Nitrification • Nitrogen is returned to the ecosystem through animals wastes and dead organisms. • Decomposers, such as bacteria, break down the waste and dead materials. • One of the products of this decomposition is ammonia. • Have you smelled ammonia? • It produces a pungent odour in a cat litter box, chicken coop, or outhouse. • Ammonia is used directly by some plants as a source of nitrogen. • As well, ammonia is converted back into nitrates by nitrifying bacteria, in a process called nitrification. • To complete a larger cycle, the nitrates in the soil or water may be converted back into nitrogen gas by denitrifying bacteria. This process involves a series of chemical changes called denitrification. Altering the Balance • Computer Lab P.56 • Groups of 3 • Complete activity “What is Organic Farming” • 2 classes • Be prepared to present to class (just stand up and say what is on your paper)