Describe the nitrogen cycle?

Question

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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

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