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Name:_________________________________________________ date:___________ Per:________ #:_______
Nitrogen Cycle Web Quest
Pre-Activity Questions:
1. Why is nitrogen such an important element to understand?
Possible answers include: Organisms need nutrients in order to survive; Nitrogen is needed to build nucleic
acids and proteins, we make fertilizer to add nutrients like Nitrogen back in to the soil.
2. List the parts of the nitrogen cycle you can remember off the top of your head:
Answers will vary. Checking this answer as they work on it will give you a good idea for where the students
are in their understanding of the nitrogen cycle
Part I: Nitrogen Cycle Animation: Go to the following website.
http://www.classzone.com/books/ml_science_share/vis_sim/em05_pg20_nitrogen/em05_pg20_nitrogen.swf
1. What is the formula for nitrogen gas in the atmosphere? ____ N2_____________
2. What happens to nitrogen in the atmosphere when it is hit by lightening?
Lightening fixes the Nitrogen by combining N with oxygen to form NO33. Do the plants use nitrogen in the form of N2 gas? ___No________
4. Besides lightening, how is nitrogen gas (N2) turned in to a form that plants can use?
Bacteria in the root nodules of some plants are able to fix the N2 gas in the soil in to a form that plants can
use. Students who are very thorough and use their notes will write specifically that it is turned to NH 4 and
then in to nitrite and nitrate.
5. How do animals obtain nitrogen?
By eating/consuming food
6. What happens to the nitrogen inside of an organism when it dies?
It decomposes and nitrogen containing compounds enter the soil.
7. How does nitrogen gas get back in to the air, completing the cycle?
Other bacteria in the soil break apart nitrogen compounds, and form N2, which can then return to the air.
Again, a student who is trying to push themselves will use their note to name this as Denitrification.
Part 2: Global Nitrogen Cycle: Go to the following website:
http://bcs.whfreeman.com/thelifewire/content/chp58/5802004.html
Read the intro, view the animation, then read the conclusion and take the quiz at the end. You will need to
answer the questions as you go. When viewing the animation choose “step through” and move on to the next
slide when you have studied the picture and read the information at the bottom. Some of the questions in this
section ask you to form an opinion – the answers to those questions must be determined using common sense
and logic – they are not necessarily answered by the text on the page.
8. Why do organisms need Nitrogen?
To produce proteins, DNA, and RNA
9. There are different compounds formed during the nitrogen cycle. Make a flow chart showing how nitrogen
compounds are rearranged in to forms that plants can use.
N2  NH4  NO2 NO3
10. Notice how the arrows showing the amounts of nitrogen moving between the different reservoirs. How do
you think the difference in Nitrogen levels in the ocean impacts the productivity of open ocean
photosynthesizers compared to those on land?
With less nitrogen available, there productivity will be lower because they will have a difficult time making
the proteins and nucleic acids needed for reproduction.
11. Humans use industrial processes to turn nitrogen gas (N2) in to fertilizer. How is that fertilizer able to enter
the nitrogen cycle in the ocean?
Nitrogen compounds run off in to waterways which lead to the ocean.
12. Again look at the numbers on the animation – how does the amount of fixation carried out by humans
compare to the amount of fixation that naturally occurs in the ocean?
Humans fix 5 times as much nitrogen in to fertilizer using industrial processes, than all of the bacteria in the
ocean. (Humans – 30 x 109 kg, Ocean – 6 x 109 kg)
13. What do you think happens to the oceanic ecosystems, or other ecosystems naturally limited by nutrients,
when too many nutrients are introduced?
Answers will vary, but a student who understands should discuss that photosynthesizers, or algae, increase
reproduction or population size.
14. What is the process called that puts nitrogen back in to the atmosphere? ____denitrification_____________
15. What happens to the nitrogen contained in the large organic molecules of living organisms when they die?
(Be specific!)
It is released. Some will be converted in to NO2, NO3, or NH4,and will continue to cycle through the soil and
organisms, but some will be converted in to N2 by bacteria and released back in to the atmosphere.
16. How have humans impacted the nitrogen cycle?
Through the creation of nitrogen fertilizers we have greatly increased the amount of nitrogen in the
environment, causing it to become a pollutant. The growth of algae has been favored over other organisms and
ecosystems have been damaged.
17. Take the quiz and initial here: __________________________ Your Score:__________________
Post Activity Question:
18. Based on what we’ve learned the last 2 days, what might you say to someone who believes that most bacteria
are bad? Use specific examples from the Nitrogen cycle in your answer.
Answers will vary but a quality answer will discuss bacteria’s unique ability to break apart N 2 and should
name specific processes such as Nitrogen fixation, nitrification, ammonification, and decomposition.
Without bacteria life on Earth would cease to exist as we would not have the nitrogen needed to make
proteins and nucleic acids.