Lundkvist
Science 10
Name: ______________________
Date:_______________Block:__
The Nitrogen Cycle
Read pages 78-83 and answer the following questions on a separate sheet of paper in complete sentences. Fill in the tables directly on this sheet.
1. What is nitrogen an important component of?
2. How is nitrogen important to
a. animals?
b. plants?
3. Complete the table below:
Form of nitrogen store
The largest store of nitrogen as nitrogen gas (N2)
Location
Other major stores of nitrogen
a.
b.
Much smaller amounts of nitrogen are also stored in
a.
b.
c.
d.
4. In the circle on the right, as a circle graph fill in the approximate amount of nitrogen that is part of the Earth’s
atmosphere.
Also write the percent in the area.
5. What is the problem with the nitrogen gas in the atmosphere?
6. What is nitrogen fixation?
7. Write the formulas for the element/compounds in the table:
Element/compound
Nitrogen gas
Nitrate
Ammonium
Formula
Did you remember to put in the subscripts and superscripts? They are important!
8. How does atmospheric fixation occur?
9. How does nitrogen fixation in the soil occur and what are bacteria called that fix nitrogen?
I think I feel worse about nitrogen than I feel about carbon dioxide.
Lundkvist
Science 10
Name: ______________________
Date:_______________Block:__
10. What is Rhizobium?
11. What are legumes? Do you eat legumes?
12. Plants and bacteria have what kind of symbiotic relationship?
13. What is the form of nitrogen that the bacteria provide for the plants?
14. Why is it good to have clover in your lawn?
15. How do cyanobacteria contribute to the nitrogen cycle?
16. What does the process of nitrification do and what are the bacteria called that do nitrification?
17. What are the two stages of nitrification?
18. How does nitrogen “travel” from the nitrifying bacteria to animals?
19. From where do decomposer bacteria and fungi get their ammonia (NH4+)?
20. What is the name of the process that returns nitrogen to the atmosphere and what do you call bacteria that
perform denitrification?
21. What do these bacteria actually do?
22. What happens to excess nitrate and ammonium that are not taken up by plants?
23. There are a lot of bacteria involved in the nitrogen cycle. Fill in the table below to show you know what they do:
Process
Take nitrogen trapped in proteins and DNA of dead
organisms
Convert NO3- into nitrogen gas
In the first step of a process, they convert NH4+ into NO2In association with legumes these ‘bugs’ convert nitrogen gas
I think I feel worse about nitrogen than I feel about carbon dioxide.
Bacteria Responsible
Lundkvist
Science 10
Name: ______________________
Date:_______________Block:__
into NH4+
In the second step of a process, they convert NO2- into NO324. Now take a good look at Figure 2.37. It will appear on your exam. Answer the questions in the table below:
Questions
What are the nitrogen stores?
Answers
In what forms is nitrogen stored in the atmosphere?
List the human activities that contribute to the nitrogen
cycle.
Nitrifying bacteria are responsible for what conversions?
How is N2 converted to NH4+ by living things?
25. What have humans done to the biosphere in the past 50 years?
26. Millions of tonnes of nitrogen are added to the atmosphere in the form of?
27. Complete the following sentences about human release of nitrogen.
a. Nitrogen is released during the burning of fossil fuels in _________________________________________________
b. Clearing forests and grasslands by burning also releases _________________________________________________
c. These compounds return to terrestrial and aquatic ecosystems as __________________________________________
d. Chemical fertilizers are made through industrial processes that ____________________________________________
e. Crops cannot assimilate all of the fertilizer they receive. As a result ________________________________________
f.
g.
h.
i.
j.
k.
l.
Ground water run-off containing these compounds enter ___________________________________________________
This increased amount of dissolved nitrogen causes _______________________________________________________
Eutrophication is the process by which excess nutrients _____________________________________________________
Run-off from acid precipitation also ________________________________________________________________________
In nitrogen-rich environments algae ________________________________________________________________________
Excessive algae growth deprives other ________________________________________________________________________
When the algae die, the oxygen used in __________________________ also deprives aquatic animals of oxygen
and can lead to _____________________________________________________________________________________________
28. Some algal blooms produce _________________________________________________________________________________
I think I feel worse about nitrogen than I feel about carbon dioxide.