1. The Nitrogen Cycle

2. Why is Nitrogen Important?
All organisms require nitrogen to live and build proteins
Where is it found?
Free nitrogen gas 78% of atmosphere
In wastes, produced by organisms
In dead and decaying organisms
Organisms must convert it to another form to use it

3. Nitrogen Fixation
Nitrifying bacteria change free N2 gas into nitrogen compounds that can be used by plants
Plants use them to make plant proteins
Animals eat the plants and use the proteins to make animal proteins
When plants and animals die, nitrogen compounds return to the soil

4. Denitrification
Denitrifying bacteria in the soil break down these nitrogen compounds into free nitrogen, which is returned to the atmosphere

5. Nutrient Cycles
Nutrients that are available in fixed quantities on Earth are passed from one organism to another and from one part of the biosphere to another.
The amount of nutrients does not change, but the form might.