1. The Nitrogen Cycle By: Caitlin, Jade, Connor, and Brandon M.

2. Nitrogen Fixation The process of combining nitrogen gas with hydrogen to form ammonia. The process of combining nitrogen gas with hydrogen to form ammonia. Only happens in absence of oxygen. Only happens in absence of oxygen. Even the tiniest bit of oxygen could ruin the entire process. Even the tiniest bit of oxygen could ruin the entire process. Nitrogen fixing bacteria live in the soil within capsules that admit no oxygen. Nitrogen fixing bacteria live in the soil within capsules that admit no oxygen.

3. Step 1:Assimilation The nitrogen-fixing bacteria produces ammonia that spreads through the soil. The nitrogen-fixing bacteria produces ammonia that spreads through the soil. The plants absorb it to make proteins, nucleic acids, and other nitrogen-containing molecules. The plants absorb it to make proteins, nucleic acids, and other nitrogen-containing molecules. Animals eat the plants and build their own molecules. Animals eat the plants and build their own molecules. Nitrogen assimilation is absorbing and incorporating nitrogen into plant and animal compounds. Nitrogen assimilation is absorbing and incorporating nitrogen into plant and animal compounds.

4. Step 2:Ammonification Animals get rid of excess nitrogen through their waste which a soil bacterium turns back into ammonia. Animals get rid of excess nitrogen through their waste which a soil bacterium turns back into ammonia. Bacteria also converts nitrogen in dead tissues to ammonia. Bacteria also converts nitrogen in dead tissues to ammonia. The ammonia is reabsorbed by plants, and it starts all over again. The ammonia is reabsorbed by plants, and it starts all over again. Ammonification is bacteria producing ammonia during the decay of nitrogen containing organic matter. Ammonification is bacteria producing ammonia during the decay of nitrogen containing organic matter.

5. Step 3:Nitrification The ammonia that is not absorbed by plants is turned into nitrate by bacteria. The ammonia that is not absorbed by plants is turned into nitrate by bacteria. Nitrate can also be absorbed by plants. Nitrate can also be absorbed by plants. Nitrification is the production of nitrate from ammonia. Nitrification is the production of nitrate from ammonia.

6. Step 4:Denitrification Another kind of bacterium turned the rest of the nitrate into nitrogen gas. Another kind of bacterium turned the rest of the nitrate into nitrogen gas. The nitrogen gas is released into the atmosphere which completes the nitrogen cycle. The nitrogen gas is released into the atmosphere which completes the nitrogen cycle. Denitrification is the conversion of nitrate to nitrogen gas. Denitrification is the conversion of nitrate to nitrogen gas.

7. Other Facts.. Atmosphere is 79% nitrogen gas. Atmosphere is 79% nitrogen gas. Nitrogen atoms are connected by a really strong triple covalent bond. Nitrogen atoms are connected by a really strong triple covalent bond. Bacteria could fix nitrogen before photosynthesis introduced oxygen. Bacteria could fix nitrogen before photosynthesis introduced oxygen. The population of plants in the ecosystem counts on how much nitrate and ammonia is in the soil. The population of plants in the ecosystem counts on how much nitrate and ammonia is in the soil. That is why farmers use fertilizer. That is why farmers use fertilizer.

8. Our Role Humans do many things to alter the nitrogen cycle. Humans do many things to alter the nitrogen cycle. We contaminate the groundwater with nitrate from the fertilizers. We contaminate the groundwater with nitrate from the fertilizers. We are releasing solid forms of nitrogen by fossil fuel combustion and forest burning. We are releasing solid forms of nitrogen by fossil fuel combustion and forest burning. Sewage wastes are releasing ammonia. Sewage wastes are releasing ammonia.

9. Resources Our Biology book. Our Biology book. http://www.physicalgeography.net/fundamenta ls/9s.html http://www.physicalgeography.net/fundamenta ls/9s.html http://www.physicalgeography.net/fundamenta ls/9s.html http://www.physicalgeography.net/fundamenta ls/9s.html

10. Questions What Percent of the Atmosphere is nitrogen gas? What Percent of the Atmosphere is nitrogen gas? A) 98% B) 79% C) 26% D) 71%

11. Which gas must be absent for nitrogen-fixation to occur? Which gas must be absent for nitrogen-fixation to occur? A) Nitrogen B) Hydrogen C) Ammonia D) Oxygen

12. What does not convert to ammonia? What does not convert to ammonia? A) Rocks B) Dead Animals C) Dead Plants D) Animal Wastes

13. Where does the nitrogen-fixing bacteria typically start out? Where does the nitrogen-fixing bacteria typically start out? A) Soil B) Plants C) Animals D) Atmosphere

14. What converts one chemical into another chemical more than once in the nitrogen cycle? What converts one chemical into another chemical more than once in the nitrogen cycle? A) Animals B) Bacteria C) Plants D) Humans

15. What happens first in the nitrogen cycle? What happens first in the nitrogen cycle? A) Assimilation B) Nitrogen-fixation C) Ammonification D) Denitrification

16. True or False Too little of nitrogen can limit plant growth in a certain area. Too little of nitrogen can limit plant growth in a certain area. Humans do not affect the nitrogen cycle. Humans do not affect the nitrogen cycle.