1. Cycles of the Earth & Biogeochemical Cycles Nitrogen Cycle
Slides 60-78

2. Nitrogen cycle:
Atmospheric nitrogen (N2) makes up nearly 78%-80% of air.
Organisms can not use it in that form.
Lightning and bacteria convert nitrogen into usable forms.

3. Nitrogen cycle:
Only in certain bacteria and industrial technologies can fix nitrogen.
Nitrogen fixation:
Convert atmospheric nitrogen (N2) into ammonium (NH4+) which can be used to make organic compounds like amino acids.
N2 NH4+

4. Nitrogen-fixing bacteria:
Nitrogen cycle:
Nitrogen-fixing bacteria:
Some live in a symbiotic relationship with plants of the legume family
(e.g., soybeans, clover, peanuts).

6. Nitrogen cycle:
Some nitrogen-fixing bacteria live free in he soil.
Nitrogen-fixing cyanobacteria are essential to maintaining the fertility of semi-aquatic environments like rice paddies.

7. The Cycle Series - Nitrogen Cycle

8. The nitrogen cycle Nitrogen comprises 78% of our atmosphere
It is contained in proteins, DNA and RNA
Nitrogen cycle = describes the routes that nitrogen atoms take through the environment
Nitrogen gas cannot be used by organisms
Nitrogen fixation = lightning or nitrogen-fixing bacteria combine (fix) nitrogen with hydrogen
To form ammonium
Which can be used by plants

10. Nitrification and denitrification
Nitrification = bacteria convert ammonium ions first into nitrite ions then into nitrate ions
Plants can take up these ions
Animals obtain nitrogen by eating plants or other animals
Decomposers get it from dead and decaying plants or other animals
Releasing ammonium ions to nitrifying bacteria
Denitrifying bacteria = convert nitrates in soil or water to gaseous nitrogen
Releasing it back into the atmosphere

11. The nitrogen cycle

12. Humans put nitrogen into the environment
Fully half of nitrogen entering the environment is of human origin

13. Nitrogen Cycle

15. Nitrogen Cycle Nitrogen needed to build DNA
Ammonia
Nitrates
Nitrogen needed to build DNA
Problem: Nitrogen in atmosphere (78%) is unusable
Step 1: Soil Bacteria
Nitrogen fixation: convert atmospheric nitrogen into ammonia
Nitrification: ammonia converted into nitrates

16. Nitrogen Cycle Step 2: Producers absorb nitrates through their roots

17. Nitrogen Cycle Step 2: Producers absorb nitrates through their roots
Step 3: Consumers ingest nitrates through the food chain

18. Nitrogen Cycle Step 2: Producers absorb nitrates through their roots
Ammonia
Ammonia
Ammonia
Step 2: Producers absorb nitrates through their roots
Step 3: Consumers ingest nitrates through the food chain
Step 4: Decomposers return ammonia to soil
Cycle repeats