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Nitrogen Cycle
url: http://www.teachersdomain.org/resource/lsps07.sci.life.eco.nitrogen/
Nitrogen Changing Processes The process by which nitrogen-fixing bacteria
in the roots of legumes change atmospheric nitrogen to nitrates is called _______________________
The process by which N2 or organic nitrogen is changed to ammonium is called____________________
The two-step process of changing ammonium to nitrate is called _______________________
The process of changing nitrate into atmospheric nitrogen is called __________________
The process of changing nitrates into organic nitrogen is called ______________________
Nitrogen fixation
Ammonification
NitrificationDenitrificati
onAssimilati
on
Nitrogen Cycle Summary
Process Bacteria N Changed from
N changed to
Nitrogen Fixation
Ammonification
Nitrification step 1
Nitrification step 2
Assimilation N/A
Denitrification
Nitrogen-fixing bacteria in
legume roots
Nitrogen in air Nitrate
Nitrogen-fixing bacteria in soil
Nitrogen in air AmmoniumDecay
bacteria and fungi
Organic nitrogen
Nitrifiying bacteria
Ammonium Nitrite
Nitrite
Nitrate
Nitrate
Organic nitrogen
Denitrifying bacteria Nitrate
Nitrogen in air
Discussion Questions
1. The atmosphere is 78% nitrogen: why do you think plants and animals can't use nitrogen as it is found in the atmosphere?
2. Explain what is meant by nitrogen fixation.
3. What is the role of bacteria in the nitrogen cycle?
4. Why don't legumes need nitrogen-containing fertilizers?
5. Why is nitrogen so important for living things?
1.Nitrogen fixation is the process that changes nitrogen from ______________
. The type of bacteria able to “fix” nitrogen are called
___________________________. Nitrogen fixing bacteria in legume roots allow
for nitrogen to be used by legume plants and become ____________________
nitrogen.
2. Nitrogen fixing bacteria in the soil change nitrogen from _________________
to ____________________ by a process called _________________________.
3. The nitrifying bacteria in the first white circle change nitrogen from
__________________________ to _____________________________ in a
process called ________________________________.
Nitrogen gas
nitrates organi
c
nitrogen gas
Ammomium
Ammonification
nitritenitrificati
on
Ammomium
4. This process is continued by a second group of nitrifying bacteria that change
nitrogen from _________________________ to _________________________.
5. Nitrates can follow one of two paths. If it is taken into a plant, it will be
_____________________________ into _____________________ nitrogen.
The chipmunk gets the nitrogen it needs by eating plants. Nitrogen containing
organic wastes from either plants or animals will be broken down by
___________________________ and ___________________________ into
__________________________________.
6. Denitrifying bacteria change nitrogen from ______________________________ to
_______________________________ returning it to the atmosphere.
nitrite
nitrates
assimilated organ
ic
decay bacteria
fungi
ammonium nitra
tenitrogen
gas