1. Nitrogen Cycle
Nitrogen moves from the air to the soil, into living things, and back to the air.

2. What is nitrogen?

3. Where is nitrogen found in the environment?

4. The largest single source of nitrogen is in the atmosphere.
Nitrogen makes up 78% of our air!

5. It’s a good thing that we have so much nitrogen because every living thing on Earth needs it. But...

6. Most organisms can’t use atmospheric nitrogen (N2) (free nitrogen)
Most organisms can’t use atmospheric nitrogen (N2) (free nitrogen). Animals can’t utilize it when they breath. Plants can’t absorb it through their leaves. So...

7. Nitrogen Fixation
N2 must be “fixed” before it can be used. Fixed- combined with other elements to make compounds. N + H4 = NH4 N + H3 = NH3

8. How is nitrogen fixed?
Most fixation is done by bacteria

9. Symbiotic Relationship Bacteria
Biological Fixation (where MOST nitrogen fixing is completed) There are two types of “Nitrogen Fixing Bacteria”
Free Living Bacteria
Symbiotic Relationship Bacteria

10. Lightning also fixes atmospheric nitrogen

11. Fixed nitrogen hangs out in the soil and can be absorbed by plants through their roots.
Plants use the nitrogen compounds to grow and reproduce.

12. So how do animals get nitrogen compounds?

13. Animals eat plants
Animals eat animals that eat plants.

14. Returned to the soil and air
When plants and animals die, decomposers (bacteria, fungi) return nitrogen compounds to the soil and release nitrogen gas back to the atmosphere.