Download Nitrogen Cycle Worksheet - Biology with​Mrs. Ellsworth

Name:_________________________Period:_________
Nitrogen Cycle Worksheet
Introduction:
 Nitrogen cannot be used directly.
 Plants and animals need nitrogen to make proteins in animals and
chlorophyll in plants.
 Animals are able to obtain nitrogen through eating plants and
animals.
 Nitrogen goes back into the soil through animal wastes and
decomposing animals and plants.
 Plants have much harder time obtaining nitrogen as they can only
absorb nitrogen when it is mixed with oxygen or hydrogen.
 Nitrogen is mixed with oxygen or hydrogen through a process
called nitrogen fixation.
 There are two ways nitrogen can be fixated:
1. Lightening
2. Bacteria in the soil or bacteria found in nodules of
legumes
 Nitrogen is a necessary component of life as plants and animals
need it to grow and to create DNA.
 The speed of decomposition is the key to keeping the nitrogen
cycle moving as the majority of fixated nitrogen comes from
bacteria breaking down dead matter and feces.
 The warmer an area is the faster decomposition will occur.
Processes in the Nitrogen Cycle
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Fixation - Fixation is the first step in the process of making
nitrogen usable by plants. Here bacteria change nitrogen into
ammonium.
Name:_________________________Period:_________
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Nitrification - this is the process by which ammonium gets
changed into nitrates by bacteria. Nitrates are what the plants
can then absorb.
Assimilation - This is how plants get nitrogen. They absorb
nitrates from the soil into their roots. Then the nitrogen gets
used in amino acids, nucleic acids, and chlorophyll.
Ammonification - This is part of the decaying process. When a
plant or animal dies, decomposers like fungi and bacteria turn the
nitrogen back in ammonium so it can reenter the nitrogen cycle.
Denitrification - Extra nitrogen in the soil gets put back out into
the air. There are special bacteria that perform this task as well.
Name:_________________________Period:_________
Nitrogen Worksheet
Questions:
1. Explain why bacteria are the most important part of the nitrogen cycle.
BACTERIA ARE ESSENTIAL TO “FIXING” THE NITROGEN SO IT CAN BE USED
BY PLANTS.
2. If nearly 78% of the atmosphere is made of nitrogen, how could there be a
shortage of nitrogen in soil?
IF NITROGEN DOES NOT GET “FIXED” BY BACTERIA THEN IT WILL NOT BE
IN A USEFUL FORM IN THE SOIL. STRAIGHT NITROGEN GAS CANNOT BE
USED BY PLANTS.
3. How do animals obtain usable nitrogen? Why is it important?
ANIMALS GET THEIR NITROGEN BY EATING PLANTS AND OTHER ANIMALS
4. Give the two ways nitrogen can be fixated so plants can use it to grow.
FIXATED BY BACTERIA
FIXATED BY LIGHTENING
5. Explain the problem if too much nitrogen enters an aquatic ecosystem.
TOO MUCH NITROGEN IN AN AQUATIC ECOSYSTEM WILL CAUSE THE
ALGAE AND OTHER PLANTS TO GROW OUT OF CONTROL. THIS DAMAGES
THE BALANCE OF THE AQUATIC ECOSYSTEM.
6. Explain the statement “Nutrients do not flow in one direction in the
ecosystem, they recycle through the ecosystem.”
NON-LIVING NUTRIENTS, SUCH AS WATER, CARBON & NITROGEN, CYCLE
THROUGH THE ENVIRONMENT. IF THE NUTRIENTS FLOWED IN ONLY ONE
DIRECTION THEY COULD NOT CYCLE AND BE REUSED.
7. What do plants and animals need nitrogen for?
NITROGEN IS USED TO BUILD PROTEINS, DNA AND GROWTH IN BOTH
ANIMALS AND PLANTS.
NITROGEN IS USED FOR CLOROPHYLL IN PLANTS.