Download The Nitrogen Cycle

The Nitrogen Cycle
318-1 illustrate the cycling of matter
through biotic and abiotic
components of an ecosystem by
tracking carbon, nitrogen and oxygen
What is Nitrogen?
• After carbon, oxygen, and hydrogen,
nitrogen is the most common element
found in living organisms.
• It is an essential part of proteins, DNA,
and other compounds.
• One of the main ingredients in fertilizer is
nitrogen.
Nitrogen Cycle
• Like carbon, nitrogen passes along food
chains and circulates between biotic and
abiotic parts of the environment.
Nitrogen Fixation
• Earth’s atmosphere is nearly 80% nitrogen
gas, but many organisms cannot absorb
nitrogen directly from the air.
• In order to be used, nitrogen atoms must
first be fixed (pulled from the air and
bonded to other elements to make new
compounds). This process is called
nitrogen fixation.
• In nature, nitrogen fixation is carried out by
a few species of nitrogen-fixing bacteria
that live in soil or water.
Example
• Nitrogen can combine with hydrogen to
make : NH4+
• Nitrogen can combine with oxygen to
make : NO3• Plants can then absorb these compounds
through their roots and use the nitrogen.
Animals can get nitrogen by eating plants
and other animals.
• After nitrogen from the atmosphere has
been fixed, it enters the soil and water.
There it is available for living organisms to
use.
• The nitrogen compounds that enter plants,
move through food chains and return to
the soil and water through dead organisms
and waste materials.
Nitrification
• Nitrogen is returned to the ecosystem
through animals wastes and dead
organisms.
• Decomposers, such as bacteria, break
down the waste and dead materials.
• One of the products of this decomposition
is ammonia.
• Have you smelled ammonia?
• It produces a pungent odour in a cat litter
box, chicken coop, or outhouse.
• Ammonia is used directly by some plants
as a source of nitrogen.
• As well, ammonia is converted back into
nitrates by nitrifying bacteria, in a
process called nitrification.
• To complete a larger cycle, the nitrates in
the soil or water may be converted back
into nitrogen gas by denitrifying bacteria.
This process involves a series of chemical
changes called denitrification.
Altering the Balance
• Computer Lab P.56
• Groups of 3
• Complete activity “What is Organic
Farming”
• 2 classes
• Be prepared to present to class (just stand
up and say what is on your paper)