Where is nitrogen found in the environment?
The largest single source of nitrogen is ________________________
Nitrogen makes up _____ of our air!
What happens to atmospheric nitrogen (N2) in the nitrogen cycle?
Atmospheric nitrogen is converted to _______________________________.
Why does atmospheric nitrogen need to be converted?
It is one of nature’s great ironies…
Nitrogen is an essential component of _____, _____ and _______—the building blocks of
life.
Although the majority of the air we breathe is nitrogen, most living organisms are unable to
use nitrogen as it exists in the atmosphere!
How does atmospheric nitrogen get changed into a form that can be used by most living
organisms?
By traveling through one of the four processes in the Nitrogen Cycle!
(1) _________________________________
(2) _________________________________
(3) _________________________________
(4) _________________________________
The first process in the nitrogen cycle is… ________________________!
What is “nitrogen fixation” and what does it mean to say nitrogen gets “fixed”?
“Nitrogen Fixation” is the process that breaks apart the N2 molecules found in the
atmosphere so they can combine with oxygen or hydrogen.
There are three ways that nitrogen gets “fixed”!
(a) ______________________
(b) ______________________
(c) ________________________
Atmospheric Fixation
(Only 5 to 8% of the Fixation Process)
The enormous energy of _________________________________________________
and enables the nitrogen atoms to combine with oxygen forming nitrogen oxides (N2O).
Nitrogen oxides dissolve in rain, forming nitrates. Nitrates (NO3) are carried to the
ground with the rain for ____________________________________.
Industrial Fixation
Under great pressure, at a temperature of 600 degrees Celsius, and with the use of a
catalyst, atmospheric nitrogen (N2) and hydrogen are combined to form ammonia (NH3).
Ammonia can be used as a _______________.
Biological Fixation
(__________________________________________)
There are two types of “Nitrogen Fixing Bacteria”

Free Living Bacteria (“fixes” 30% of N2)

Symbiotic Relationship Bacteria (“fixes” 70% of N2)
Free Living Bacteria
Highly specialized bacteria live in the soil and have the ability to combine atmospheric
nitrogen with hydrogen to make ammonia (NH3).
Symbiotic Relationship Bacteria
Bacteria live in the roots of legume family plants and provide the plants with ammonia
(NH3) in exchange for the plant’s carbon and a protected home.
Most atmospheric nitrogen (N2) is “fixed” and changed to ammonia (NH3). Ammonia is
highly toxic to many organisms.
Can plants use ammonia?
Very few plants can use ammonia (NH3)… …but, fortunately the second process
Ammonification can help!
What is ammonification?
Ammonification: ___________________________________________________________
_________________________________________________________________________
What happens to ammonium (NH4) stored in the soil?
It travels through the third process of the nitrogen cycle called Nitrification!
Nitrifying bacteria in the ground convert the ammonium to nitrites then nitrates which
green plants can absorb and use!
How does nitrogen re-enter the atmosphere in the nitrogen cycle?
Through the fourth process called denitrification!
What does denitrification do?
Denitrification converts nitrates (NO3) in the soil to atmospheric nitrogen (N2) replenishing
the atmosphere
How does the denitrification process work?
Denitrifying bacteria live deep in soil and in aquatic sediments where conditions make it
difficult for them to get oxygen. The denitrifying bacteria use _____________________
______________________________________________________________________,
leaving free nitrogen gas as a byproduct. They close the nitrogen cycle!
Other ways that nitrogen returns to the atmosphere…
______________________________________ and ___________________________ create
nitrous oxides gas (N2O).
____________________________ emit nitrous oxides gas (N2O).