The Nitrogen Cycle
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What is nitrogen used for?
Nitrogen is a component of many organic molecules.
It forms an essential part of amino acids (which make up proteins) and
DNA. Nitrogen is essential for all living cells.
What is the nitrogen cycle?
Nitrogen is the major component of earth's atmosphere.
It enters the food chain by means of nitrogen-fixing bacteria and algae
in the soil. This nitrogen which has been 'fixed' is now available
for plants to absorb. These types of bacteria form a symbiotic relationship
with legumes--these types of plants are very useful because the nitrogen
fixation enriches the soil and acts as a 'natural' fertilizer. The
nitrogen-fixing bacteria form nitrates out of the atmospheric nitrogen
which can be taken up and dissolved in soil water by the roots of plants.
Then, the nitrates are incorporated by the plants to form proteins, which
can then be spread through the food chain. When organisms excrete
wastes, nitrogen is released into the environment. Also, whenever
an organism dies, decomposers break down the corpse into nitrogen in the
form of ammonia. This nitrogen can then be used again by nitrifying
bacteria to fix nitrogen for the plants.
What are the effects of human interference in the nitrogen
How have humans interfered with the nitrogen
When we cause nitrogen overload in an ecosystem,
there are many drastic effects. Dumping of raw sewage contains nitrogenous
wastes, along with urban runoff. When large amounts of nitrogen collect
in a water body, eutrophication can result. This is an accumulation
of excess nutrients which causes an algae bloom. The algae rapidly
deplete all of the oxygen in the water, making it inhospitable for fish
and other aquatic organisms. Eutrophication also brings about the
deadly red tides. When plant communities are saturated with nitrogen,
the soil can become acidified. This makes the soil inhospitable.
Burning fossil fuels and wood contributes to a large amount of nitric oxide
in the atmosphere. Nitric oxide can combine with oxygen gas to for
nitrogen dioxide, which reacts with water vapor to form a strong acid (nitric
acid). This can precipitate out of the atmosphere in the form of
the deadly acid rain. The acid can damage
trees and kill fish. The use of inorganic fertilizers and depleting
nitrogen resources by overharvesting legumes (which have nodules in their
roots formed by a symbiotic bacteria that fix nitrogen) and overmining
nitrogen also alter an ecosystem.
Go back to ecosystems
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