Download Nitrogen Cycle

NITROGEN CYCLE
Teacher Copy
Mineralization
Processes of Nitrogen Cycle
•Nitrogen Fixation (includes Ammonification)
•Nitrification
•Assimilation (nitrogen uptake)
•Mineralization (decay)
•Denitrification
1. Nitrogen Fixation
•Fixation= turning N2 into a usable
form for plants and animals
• Fixation happens mostly from
bacteria in the soil or in root
nodules of legumes (like beans or
peas)
• Can also happen from lightning
or volcanic activity
1. Nitrogen Fixation
• The bacteria in the soil or roots
turn N2 into Ammonium (NH4+)
• This is also known as
ammonification
• Plants can then absorb this
ammonium (although it is not their
preferred way to absorb N because
ammonium is toxic in large
quantities).
2. Nitrification
•NH4+ into NO3•Nitrifying bacteria turn
ammonium (NH4+) into
nitrites (NO2-) and then into
nitrates (NO3-)
• Nitrates are the compounds
that plants usually use to
gain N.
Mineralization
2. Nitrification
•NO3- is easily dissolved into water, which makes it
easy for plants to absorb it through their roots but it
also makes it easy to get washed out (leached) of
the soil into nearby water sources
• This leaching can lead to eutrophication and loss of
soil nutrients
Checks for Understanding
•1. What is the formula for atmospheric N?
•2. What does it mean when we fix N?
•3. List 2 ways that nitrogen can be fixed.
•4. What form is N converted into when it is
“fixed?”
•5. What is the term for turning N2 into NH4+?
Checks for Understanding
1.N2
2.It is turned into a form that plants/animals can
use
3.Lightning, volcanoes, N. fixing bacteria (mostly)
4.NH4+
5.Ammonification or Nitrogen Fixation
Checks for Understanding
•6. What is the term for turning NH4+ into NO3-?
• 7. What does NH4+ stand for?
•8. What does NO3- stand for?
•9. What organisms cause nitrification?
•10. What form of N do plants prefer to absorb?
•11. Which form of N is easily leached out of soil?
Checks for Understanding
•6. Nitrification
•7. Ammonium
•8. Nitrates
•9. Nitrifying bacteria in the soil
•10. NO3•11. NO3-
3. Assimilation (Uptake)
•Turns NH4+ or NO3- into organic Nitrogen (N in
living things)
•The ammonium or nitrates produced by N-fixing
bacteria are absorbed by a plant, which turns it into
organic Nitrogen by incorporating it into proteins or
DNA.
•When animals eat plants (or other animals), they gain
organic nitrogen from the organisms they are eating
Mineralization
4. Mineralization
• Organic N into NH4+
• When organisms die, bacteria or
fungi decompose the organism
and convert the organic N into
NH4+ (ammonium)
• This is called mineralization.
• The NH4+ can either be absorbed
by a plant or nitrified into NO3-
5. Denitrification
•NO3- into N2
• Denitrifying bacteria turn nitrates (NO3-) into
atmospheric N2
•It can also turn into small amounts of nitrous oxide
(N2O), which leads to acid rain
•This is the only process that removes N from the
fixed reservoirs within ecosystems.
•It should balance the amount of nitrogen fixed.
Nitrogen Cycle Animation
• ** There isn’t any one way for Nitrogen to move
through the cycle.
• There are multiple pathways that a N atom can take.
• Why is the Nitrogen Cycle Important?
• Nitrogen is essential for life. Without Nitrogen to
make proteins and DNA, organisms will not survive.
HOW NITROGEN GETS INTO WATER
• Runoff – Washes fertilizers/manure/urine into water
• Acid rain
• From either denitrifying bacteria or burning fossil fuels
releasing N2O into the air, eventually forming acid rain
• Animal waste
• Urea is found in animal urine, which can be found in waterways
or leached from the soil into waterways
• Soil Leaching
• Nitrates are leached from the soil into nearby waterways
Human Impact on Nitrogen Cycle
•Fertilizers add synthetic N into water and soil
•Can cause eutrophication
•Burning Fossil Fuels
•Releases nitrous oxides into atmosphere, leading
to acid rain
•Sewage & Livestock
•Animal and human waste adds nitrogen to soil &
water
Checks for Understanding
•1. What is the term for plant/animal uptake of N?
•2. In what two forms can plants absorb N?
•3. What do plants and animals turn N into?
•4. Mineralization turns ____ into ____.
•5. When does mineralization occur?
•6. What organisms cause mineralization?
Checks for Understanding
1.Assimilation
2.NH4+ and NO3-
3.Proteins and DNA
4.Organic N into NH4+
5.During decomposition of organisms
6.Bacteria or fungi
Checks for Understanding
Denitrification turns _____ into ________ or
_________.
8. What organisms cause denitrification?
9. Why is denitrification important?
10.How does N get into rivers or lakes?
11.List 3 ways that humans impact the N cycle.
7.
Checks for Understanding
7. NO3- into N2 or N2O
8. Denitrifying bacteria
9. It balances out the amount of N2 in the
atmosphere and the N fixed.
10. Runoff, leaching, animal urine & acid rain
11. Fertilizers add N, burning fossil fuels (adds
N2O) and Livestock/sewage (adds N)