Download Nitrogen Cycle Packet key

Name _______________KEY________________
Period _______
Nitrogen Cycle Packet
What is Nitrogen?
Nitrogen is an element found in the organisms on our planet, the atmosphere, water and soil.
Living things cannot exist without nitrogen- it is an essential nutrient that living things use to make
proteins and DNA. Atoms of nitrogen move slowly between living things, dead things, the air, soil and
water. These movements are called the nitrogen cycle. Reservoirs are the areas where nitrogen is stored,
such as the atmosphere, living organisms, soils and bodies of water.
Most of the nitrogen on Earth is found in the atmosphere. Almost 80% of
the air we breathe is made up of nitrogen. In the air, nitrogen is found as N2,
which is two nitrogen atoms bonded together by a very strong triple bond.
Because this bond is so strong, it is difficult to break the N2 into forms that plants
N2
and animals can use to make proteins and DNA. In order for living things to use
atmospheric nitrogen (N2), it must be converted into a different form such as those found in the soil or
water [nitrate (NO3-) or ammonium (NH4+)] or into organic nitrogen (found in organisms). Plants take in
nitrogen from the water through their roots and animals take in nitrogen by eating other plants/animals
which contain proteins made partially of nitrogen. Nitrogen cycles throughout these different forms all
the time.
1. What is nitrogen used for in living things? _____PROTEINS AND DNA________
2. List 4 reservoirs where nitrogen can be found on Earth.
ATMOSPHERE, SOIL, GROUND WATER, OCEANS
________________________________________________________________________
3. Where is the majority of Nitrogen found on Earth? ATMOSPHERE
4. In what form is atmosphere nitrogen? ATMOSPHERE= N2 IN GAS FORM
5. Why is it difficult to convert atmospheric nitrogen into a usable form?
IT HAS A TRIPLE BOND BETWEEN NITROGEN ATOMS THAT IS VERY HARD TO
BEAK BY PLANTS AND ANIMALS.
6. List 3 other forms that nitrogen is found in other than atmosphere nitrogen.
NO2 -, NO3-, NH4+ and N2O
7. Where is organic nitrogen found? IN LIVING THINGS.
8. Write the letter that matches each term for the diagram below.
A
B
O
C
N
P
D
F
L
E
G
M
K
H
J
I
_O_ Denitrification
_E_Nitrogen Fixation
_P_ Assimilation
_K_Nitrification (2)
_C_Organic Nitrogen
_G_Mineralization
_L_ Nitrates (NO3-)
_M_ Leaching
_N_Denitrifying bacteria
_A_ Atmospheric N2
_F_ Decomposers
_D_Nitrifying bacteria
_B_ Lightning Fixation
_J_ Nitrites (NO2-)
_H_ Ammonium (NH4+)
9. Fill in the chart below:
Compound
Atmospheric N
Nitrates
Nitrites
Formula
N2
NO3-
Compound
Ammonium
Formula
NH4+
Nitrous Oxides
N2O
NO2-
10. Fill in the conversions below with the correct formulas (use the chart from #9 to help):

Nitrogen fixation (ammonification) turns _____ N2______ into _____ NH4+____.

Nitrification turns _____ NH4+______ into _____NO2-______ and finally into ____ NO3-_____.

Assimilation turns _____ NO2-_____ or _____ NO3-________ into __ORGANIC
NITROGEN_____.

Mineralization turns into __ORGANIC NITROGEN____into ______ NH4+_______.

Denitrification turns ___NO3-______ into ______N2________ or _______N2O_______.
11. Explain how humans are contributing to the Nitrogen cycle (do not just list them).
•
Fertilizers add synthetic N into water and soil
•
•
Burning Fossil Fuels
•
•
Can cause eutrophication
Releases nitrous oxides into atmosphere, leading to acid rain
Sewage & Livestock
•
Animal and human waste adds nitrogen to soil & water
12. List 4 ways that nitrogen gets into rivers or lakes, causing eutrophication.
Runoff – Washes fertilizers/manure/urine into
Acid rain: From either denitrifying bacteria or
water
burning fossil fuels releasing N2O into the air,
eventually forming acid rain
Animal waste :Urea is found in animal urine,
Soil Leaching: Nitrates are leached from the soil
which can be found in waterways or leached from
into nearby waterways
the soil into waterways
Use the word bank to fill in the blanks below:
Word Bank
Denitrifying
Assimilation
Nitrifying
Proteins
Roots
Mineralization
Nitrates
Ammonium
Decomposes
Leached
Atmospheric N2
Organic N
13. Bacteria found in ____ Roots ____ of legumes, in the soil, or lightning can fix nitrogen from
atmospheric nitrogen into __ Ammonium ___, a form that plants can use.
14. _____ Nitrifying _______ bacteria turn ammonium (NH4+) into _________ Nitrates ___________
(NO3-), which is the form of Nitrogen that plants prefer to absorb. This is also the form that is easily
________ Leached _______ from the soil.
15. During _____ Assimilation ______, plants absorb NO3- or NH4+ and turn the N into ____ Organic
Nitrogen ________, eventually making ______ Proteins ______ or DNA.
16. During _____ Mineralization ______, organic N is converted into ammonium (NH4+) when an
organism _____ Decomposes ______.
17. _________ Denitrifying __________ bacteria turns nitrates (NO3-) into _ Atmospheric N2 ,
completing the nitrogen cycle.
Challenge Question:
18. How will an excess of nutrients from fertilizers in the rivers and lakes affect the food chain
(particularly the animals that eat plants)?
Excess nitrogen makes algae bloom killing many of the underwater plants. Algae is not a plant
form that many animals eat so this will impact their food source. Furthermore, as eutrophication
of the waterway continues the animals will die from a lack of D.O. in the water causing a shortage
of food to other species that eat fish, amphibians or crustaceans. Eventually as the waterway dies
all species will need to find a new source of food and the waterway will be dead and anoxic.