The Nitrogen Cycle
Nitrogen is essential for all living things as it is needed to make protein, chlorophyll, and other vital substances. There is plenty of it, as the atmosphere is 78% nitrogen. However, bacteria are the only living organisms that can use nitrogen in that form (gas), so it must be ‘fixed’ into a usable form for other organisms.
Nitrogen is fixed when it is combined with oxygen to form nitrate. This happens in two ways:
1) Bacteria living in the soil, or in close association with plants, fix atmospheric nitrogen. Some bacteria form root nodules on the roots of plants, for example legumes and wattles.
2) Lightning flashes trigger chemical reactions that will also fix nitrogen.
Nitrogen reaches animals through plants, which absorb nitrates through their roots. When living things die or excrete waste, nitrogen is returned to the soil.
Ah, the circle of li- Well, nitrogen. The nitrogen cycle.