1. What is the Nitrogen Cycle?

2. Root Words Node Knot Nodules Re Again Recycle Cycl Circle
Nitrogen Cycle
Atmo
Vapor
Atmosphere
Troph
Nourishment
Trophic level

4. What is Nitrogen? N for Nitrogen
Necessary building block in living things
Air = 78% Nitrogen gas
“Free Nitrogen” – not combined with any other element

5. Why do we need Nitrogen?
All living organisms need nitrogen in order to build proteins and build DNA
Most animals get the nitrogen they need by eating plants.

6. Nitrogen Cycle
The process by which nitrogen is removed from the atmosphere, fixed in the soil by bacteria, incorporated in other living things, and then released back into the atmosphere.

7. Available Nitrogen
Nitrogen must be combined with something else in order for it to be used
Most organisms can NOT use the nitrogen in the air
Nitrogen must be “fixed”
needs to be combined with other elements

8. Nitrogen Fixation
The process of changing free nitrogen gas (from the air) into a usable form of nitrogen
Performed by bacteria

9. Bacteria
Some of these bacteria live in bumps called nodules on the roots of certain plants.

11. What kind of plants?
Bacteria live in the roots of plants called legumes
Example: Clover, beans, peas, alfalfa, and peanuts

12. Farmers
Farmers will often plant alfalfa in their fields so that their soil will be rich in nitrogen
Bacteria in the roots “fix” the nitrogen so it can be used.

13. Now What?
Once bacteria in the roots of plants have “fixed” the nitrogen, the nitrogen can be used by organisms to build proteins and other complex substances.
Plants absorb the nitrogen
Animals eat the plants

14. Recycling
Decomposers break down these complex compounds in animal wastes and in the bodies of dead organisms.
Nitrogen is now returned to the soil
Nitrogen can be recycled over and over again
Bacteria can also return “free” nitrogen back to the air.

15. Human Influence Nitrogen enhanced fertilizer Chemical fertilizers
Is this considered organic?
Cow manure has lots of nitrogen!
What do cows eat?
Pollution

16. Question…
Nitrogen fertilizer is often added to soil to increase the growth of crops. Which of these ecosystems would most likely be harmed by the use of nitrogen fertilizer?
Forest
Pond
Park
Meadow

17. Answer
In this example, water ecosystems would be harmed the most from fertilizer runoff, making Choice B, a pond, the correct answer.
Fertilizer would increase the growth of water plants and algae, thus reducing the resources for some living organisms in the pond.

18. Journal Activity 1. Fold your notes in half and glue 2
Journal Activity 1. Fold your notes in half and glue 2. Trim around the nitrogen cycle 3. Color the n.cycle and glue

20. Foldable
Figure 3-14 on page 78