2. The Nitrogen Cycle: Who Cares? Nitrogen is an essential component of the amino acids that make up proteins and is a basic element of living things.

3. Elements Essential for Life Carbon, Oxygen, and Hydrogen: needed to create sugars (C 6 H 12 O 6 )& carbohydrates. These are used for energy by living things Carbon, Oxygen, Hydrogen, and Nitrogen: needed to create amino acids & proteins. These are used for building tissue by living things.

4. Nitrogen, Nitrogen Everywhere! 78% of our atmosphere is made up of nitrogen. Atmospheric nitrogen is N 2 Most organisms can NOT use N 2 because of its strong triple bonds (N=N) Nitrogen in the atmosphere must be chemically changed into a form that living things can absorb Nitrogen must be changed into nitrates (NO 3 ) or ammonia (NH 4 )

5. How Nitrogen is Fixed into a Usable Form Nitrogen Fixation: the process used to transform atmospheric nitrogen in to a usable form Accomplished by bacteria like (i.e. Rhizobia) and blue- green algae A group of nitrogen-fixing bacteria in soil converts nitrogen into nitrate (NO 3 ) Rhizobia are the most important of the nitrogen- fixing bacteria that live in nodules on the roots of legumes like the pod-bearing plants such as soybeans, peas, beans, and alfalfa

6. Rhizobia

7. Watch this!

8. Atmosphere Nitrate NO 3 Nitrogen-fixing Bacteria (Rhizobia) on roots of legumes in nodules N2N2 Denitrifying Bacteria convert nitrates to nitrogen gas (N 2 ) and return it back to the atmosphere (70% of air is made of N 2 ) (Nitrogen Gas) Denitrifying Bacteria N2N2 (Nitrogen Gas) NO 3 Legume Plant Nitrogen-fixing Bacteria change N 2 to Nitrate (NO 3 ) And so begins the cycle again…

9. Atmosphere Nitrate NO 3 Nitrogen-fixing Bacteria (Rhizobia) on roots of legumes in nodules N2N2 Denitrifying Bacteria convert nitrates to gas (N 2 ) and return nitrogen to the atmosphere (Nitrogen Gas) Denitrifying Bacteria N2N2 (Nitrogen Gas) NO 3 Legume Plant Nitrogen-fixing Bacteria change N 2 to Nitrate (NO 3 ) And so begins the cycle again…

10. Nitrogen Cycle Like legume plants, lightning can fix nitrogen too Nitric Acid N 2 O N2N2

11. Nitrifying Bacteria Other specialized bacteria convert the ammonia into nitrites (NO 2 ) and then nitrates (NO 3 ) Plants can only absorb nitrates or ammonium This happens through their roots and are then passed on to organisms that eat them

12. Denitrifying Bacteria All of these activities would tend to stockpile nitrogen in the soil if it were not for another set of microorganisms Denitrifying bacteria are organisms that break down nitrogen-containing substances and return N 2 gas back into the atmosphere

13. More Bacteria in the Nitrogen Cycle! One of the major sources of nitrogen containing materials comes from waste products of animals (feces and urine) and from the decomposition of dead animals and plants. Bacteria convert these nitrogen-containing wastes into ammonia (NH 3 ) and ammonium (NH 4 )

14. Nitrogen Cycle A Smaller Cycle within the Nitrogen Cycle NO 3 Nitrate Feces & Urine (NH 4 ) Nitrifying Bacteria Animal Wastes or dead animal/plant matter is/are decomposed Legume Plant

15. Eutrophication Watch this…

16. Homework! Read pages 57-60 and 63 Answer the following questions What are the 5 human impacts and how do they affect the nitrogen cycle? Name three ways in which nitrogen can be fixed