The nitrogen cycle?

Question

how would i describe the nitrogen cycle when i am taking the ap exam. in like simple english. please and thank you

Answer 1

Nitrogen is constantly being recycled in the nitrogen cycle. Here is how:

1. The atmosphere contains about 78% nitrogen gas, N2. This is very unreactive so it can't be used directly by plants or animals.

2. Nitrogen is needed for making proteins for growth, so living organisms have to get it somehow.

3. Plants get their nitrogen from soil, so nitrogen in the air has to be turned into nitrogen compounds before plants can use it. Animals can only get proteins by eating plants or other animals.

4. Decomposers break down proteins in rotting plants and animals, and urea in animal waste, into ammonia. So the nitrogen in these organisms is recycled.

5. Nitrogen fixation is the process of turning N2 from the air into nitrogen compounds in the soil which plants can use. There are two main ways this happens:

a) Lightning- there’s so much energy in a bolt of lightning that it’s enough to make nitrogen react with oxygen in the air to give nitrates.

b) Nitrogen-fixing bacteria in roots and soil.

6) There are four different types of bacteria involved in the nitrogen cycle:

a) Decomposers- decompose proteins and urea and turn them into ammonia.

b) Nitrifying bacteria- turn ammonia in decaying matter into nitrates.

c) Nitrogen-fixing bacteria- turn atmospheric N2 into nitrogen compounds plants can use.

d) Denitrifying bacteria- turn nitrates back into N2 gas. This is of no benefit to living organisms.

Answer 2

1) the main reservoir of all the nutrients is in an abiotic compartment, not in living organisms

2) initial introduction of the nutrient from some abiotic compartment to living organisms is usually through primary producers

3) micro-organisms (bacteria and fungi) are often critical in at least some stages of all the cycles

Answer 3

Atmospheric nitrogen is 'fixed' by certain bacteria who use and enzyme to combine nitrogen and hydrogen into ammonia, which is then converted into other organic compounds.  These are then used by other plants and animals to make chlorophyll and amino acids. There are other bacteria that can break down ammonia into nitrites and into nitrates and back into gaseous nitrogen - completing the cycle.

For a diagram see

http://en.wikipedia.org/wiki/Image:Nitro...