Download The Nitrogen Cycle

N2
Nitrogen Cycle
• What is the NITROGEN CYCLE?
• The atoms of nitrogen moves from the
atmosphere to the soil, through plants and
animals, and back into the atmosphere.
Nitrogen in the Atmosphere
• Most of the nitrogen on Earth is in the
atmosphere.
• The atmosphere is a mixture of nitrogen
(78%), oxygen (21%), and other gases
(1%) that surround Earth.
Nitrogen Cycle
• What is the purpose of NITROGEN to our
ecosystems and planet?
• Nitrogen is the basic building blocks for:
– Nucleotides of DNA and RNA
– Amino Acids in Proteins.
Nitrogen in the Atmosphere
• Free Nitrogen:
atoms of nitrogen are found in Earth’s
atmosphere bonded in pairs – N2
Nitrogen in the Soil
•*N2 is unusable to plants and animals.
•When the N2 bonds are broken the nitrogen
atoms are “free” to bond with other
elements forming nitrogen compounds.
•Primary compounds are NH3 and NH4
• This process is called Nitrogen Fixation.
Nitrogen in the Soil
• NITRITES (NO2)- AND NITRATES (NO3)-
• Special bacteria can convert NH3 and NH4
into nitrites and nitrates.
• Some of this bacteria is located in the soil
• Some of this bacteria is located in the roots
of LEGUMES
Examples of Legumes: Soybeans, Alfalpha, Peas, Clover, and Peanuts.
Plants LOVE Nitrates!
• Plants use nitrates to form proteins
which promote healthy growth.
• Not enough nitrates can stunt growth
• Too much can burn plants and cause
other environmental problems.
Nitrogen and Decomposers
• Animals and Plants die and the decaying
process puts more NH3 and NH4 into the soil.
DECOMPOSERS convert organic material into
many substances including NH3 and NH4
Examples of DECOMPOSERS: Fungi, aerobic and
anaerobic bacteria
Nitrogen in Animals and Plants
• Animals get the nitrogen they need by eating
plants or other animals that contain nitrogen.
• Most plants get the nitrogen they need to
grow from the soils or water in which they
live.
Nitrogen in the Soil and Water
• Other types of bacteria are able to
change nitrogen dissolved in waterways
into a form that allows it to return to the
atmosphere.
Human Effect on the
Nitrogen Cycle
• Certain actions of humans are causing changes to the nitrogen
cycle and the amount of nitrogen that is stored in the land,
water, air, and organisms. The use of nitrogen-rich fertilizers
can add too much nitrogen in nearby waterways as the
fertilizer washes into streams and ponds. The waste
associated with livestock farming also adds large amounts of
nitrogen into soil and water. The increased nitrate levels cause
plants to grow rapidly until they use up the supply and die.
The number of plant-eating animals will increase when the
plant supply increases and then the animals are left without
any food when the plants die.
The Nitrogen Cycle
Nitrogen is an element. It is found in living things like plants and animals. It is also an important
part of non-living things like the air above and the dirt below. Atoms of nitrogen don't just stay
in one place. They move slowly between living things, dead things, the air, soil and water. These
movements are called the nitrogen cycle.
Most of the nitrogen on Earth is in the atmosphere. Approximately 80% of the molecules in
Earth's atmosphere are made of two nitrogen atoms bonded together (N2). All plants and
animals need nitrogen to make amino acids, proteins and DNA, but the nitrogen in the
atmosphere is not in a form that they can use. The molecules of nitrogen in the atmosphere can
become usable for living things when they are broken apart during lightning strikes or fires, by
certain types of bacteria, or by bacteria associated with bean plants.
Most plants get the nitrogen they need to grow from the soils or water in which they live.
Animals get the nitrogen they need by eating plants or other animals that contain nitrogen.
When organisms die, their bodies decompose bringing the nitrogen into soil on land or into
ocean water. Bacteria alter the nitrogen into a form that plants are able to use. Other types of
bacteria are able to change nitrogen dissolved in waterways into a form that allows it to return
to the atmosphere.
Certain actions of humans are causing changes to the nitrogen cycle and the amount of nitrogen
that is stored in the land, water, air, and organisms. The use of nitrogen-rich fertilizers can add
too much nitrogen in nearby waterways as the fertilizer washes into streams and ponds. The
waste associated with livestock farming also adds large amounts of nitrogen into soil and water.
The increased nitrate levels cause plants to grow rapidly until they use up the supply and die.
The number of plant-eating animals will increase when the plant supply increases and then the
animals are left without any food when the plants die.
Last modified May 7, 2007 by Lisa Gardiner.
Lightning converts some
atmospheric nitrogen into
nitrates that organisms can
use.
Atmospheric nitrogen, N2
Runoff
Nitrogen-fixing
bacteria in soil
and root nodules
produce ammonia, NH .
Aquatic bacteria
also process nitrogen.
Bacteria in soil and
water add nitrogen
to the atmosphere.