The Nitrogen Cycle
Nitrogen, like water, is recycled through
ecosystems over and over....
Take a deep breath!
78% of the air you just breathed
in is made up of nitrogen gas.
Your body requires nitrogen to
build proteins, amino acids, and
DNA, but your body cannot use the
nitrogen gas you just breathed in.
Look at the diagram on page 52 of
your textbook to see where
consumers like us (and the sheep
in the diagram!) get nitrogen.
The Nitrogen Cycle
Nitrogen
a necessary building block of living organisms
used to make proteins, amino acids, and DNA
found in atmosphere
78% of atmosphere is free nitrogen gas (N2)
cannot be used by most organisms
nitrogen fixation
nitrogen is "fixed" by combining with other
elements to form nitrogen-containing compounds
these compounds can be used by living things
performed by certain kinds of bacteria
nitrogen can also be fixed by lightning strikes
legumes
plants which contain nitrogen fixing bacteria in
nodules in their roots (e.g. clover, beans, peas,
alfalfa, peanuts)
Where do
producers
get nitrogen?
plants take up simple nitrogen compounds from
the soil and use it to build proteins and other
complex nitrogen compounds
Where do
consumers
get
nitrogen?
consumers get nitrogen by consuming
producers or other consumers.
Good sources of protein
(and therefore nitrogen)
Where do
decomposers
get nitrogen?
by breaking down complex nitrogen compounds
in animal wastes and dead organisms
this process (decomposition) returns simple
nitrogen compounds to the soil.
How does
nitrogen
back into the
atmosphere?
some bacteria break down nitrogen compounds
completely, releasing free nitrogen back into
the atmosphere.
The
Nitrogen
Cycle
Nitrogen
moves
from the
atmosphere to
the soil, into
living
organisms, and
back
into the
atmosphere.
The nitrogen in your body might
once have been in the body of a..
Wooly mammoth!
or a glyptodont!
or maybe a giant ground sloth
or even Cleopatra!
And if you eat meat, some of the
nitrogen making up your body was
once part of the body of whatever
animal you ate!
The Nitrogen Cycle in an Aquarium
Forms of Nitrogen
1. Ammonia- (NH3) Waste product of animals released during excretion.
Ammonia is toxic to most organisms.
2. Ammonium- (NH4+) When ammonia is mixed with water, it grabs another
hydrogen from the water molecules and makes ammonium. This is the only
way you will ever see ammonia in nature. Also, it tends to stick to soil and
clay particles instead of being washed away like nitrate.
3. Free Nitrogen- (N2) This is a gas and is one of the most abundant gases
in the atmosphere.
4. Nitrate- (NO3-) This is usually found as a liquid and is very easily washed
out of the soil and into groundwater or streams. Farmers don't like when
their fertilizer gets turned into this, because it washes away too easily and
isn't always in the soil long enough to help their plants.
5. Nitric Acid- (HNO3) This is the form of nitrogen in acid rain. It is also
made by lightning.
6. Nitrite- (NO2-) This is a middle step during the process of nitrification. It is
very toxic to organisms. In a new fish tank, nitrite can build up because the
next step of nitrification can't continue until all the ammonium is gone, so
you have to carefully measure NO2- when you first add fish to a tank.
7. Nitrogen oxides- (N2O and NO) These are greenhouse gases and are a
middle step (intermediate) between nitrate and N2 gas.
8. Organic Nitrogen- (CaHbNcOd) Organic molecules containing nitrogen
come in many forms from amino acids to proteins to lipids.