1. The Nitrogen Cycle

2. Nitrogen Cycle
1. Our atmosphere contains about 20% oxygen, _____% nitrogen, and 1% other gases. 78

3. Nitrogen Cycle
2. The process in which soil bacteria (like Rhizobium) converts atmospheric nitrogen (N2) into ammonia (NH3) is called
a. Assimilation
b. Nitrification
c. Nitrogen fixation
Rhizobium
d. De-nitrification

4. Nitrogen Cycle
3. Plants called legumes have nodules on their roots that host nitrogen-fixing bacteria. What are some examples of legumes?
nodules
Peanuts
Peas
Alfalfa

5. Nitrogen Cycle
4. When plants and animals die their remains are decomposed by soil bacteria (like Bacillus) to yield ammonia (NH3) and ammonium (NH4+). This process is called
a. Assimilation
b. Ammonification
c. Nitrogen fixation
d. De-nitrification
Detritus

6. Nitrogen Cycle
5. Herbivore waste products like __________ and _________ are high in nitrogen content.
urine
manure

7. Nitrogen Cycle
6. In ammonification, ammonia (NH3) is stored in the soil in the form of ___________________
ammonium ions (NH4+)

8. Nitrogen Cycle
7. Soil bacteria (like Nitrobacter) change ammonium (NH4+) into nitrates (NO3-) in a process called
a. Nitrification
b. Ammonification
c. Nitrogen fixation
d. De-nitrification

9. Nitrogen Cycle
8. Plants take up ammonium (NH4+) and nitrates (NO3-) through their root hairs in a process called
a. Assimilation
b. Ammonification
c. Nitrogen fixation
d. De-nitrification

10. Nitrogen Cycle
9. During denitrification, bacteria (like Clostridium) convert nitrate (NO3-) back into _______________ gas, which is then released into the atmosphere.
Nitrogen (N2)

11. Nitrogen Cycle Complete the diagram. 10. 17. 16. 11. 14. 13. 15. 11.
Processes:
Ammonification
Assimilation by Plants
Denitrification
Nitrification
Nitrogen fixation
Compounds:
Atmospheric Nitrogen (N2)
Ammonium (NH4+)
Nitrate (NO3-)
Nitrogen Cycle
Complete the diagram.
10.
17.
16.
11.
14.
13.
15.
11.
12.

12. Atmospheric nitrogen (N2)
Processes:
Ammonification
Assimilation by Plants
Denitrification
Nitrification
Nitrogen fixation
Compounds:
Atmospheric Nitrogen (N2)
Ammonium (NH4+)
Nitrate (NO3-)
Nitrogen Cycle
Complete the diagram.
Atmospheric nitrogen (N2)
17.
16.
11.
14.
13.
15.
11.
12.

13. Atmospheric nitrogen (N2)
Processes:
Ammonification
Assimilation by Plants
Denitrification
Nitrification
Nitrogen fixation
Compounds:
Atmospheric Nitrogen (N2)
Ammonium (NH4+)
Nitrate (NO3-)
Nitrogen Cycle
Complete the diagram.
Atmospheric nitrogen (N2)
17.
16.
Nitrogen Fixation
14.
13.
15.
Nitrogen Fixation
12.

14. Atmospheric nitrogen (N2)
Processes:
Ammonification
Assimilation by Plants
Denitrification
Nitrification
Nitrogen fixation
Compounds:
Atmospheric Nitrogen (N2)
Ammonium (NH4+)
Nitrate (NO3-)
Nitrogen Cycle
Complete the diagram.
Atmospheric nitrogen (N2)
17.
16.
Nitrogen Fixation
14.
13.
15.
Nitrogen Fixation
Ammoniuim (NH4+)

15. Atmospheric nitrogen (N2)
Processes:
Ammonification
Assimilation by Plants
Denitrification
Nitrification
Nitrogen fixation
Compounds:
Atmospheric Nitrogen (N2)
Ammonium (NH4+)
Nitrate (NO3-)
Nitrogen Cycle
Complete the diagram.
Atmospheric nitrogen (N2)
17.
16.
Nitrogen Fixation
14.
Ammonification
15.
Nitrogen Fixation
Ammoniuim (NH4+)

16. Atmospheric nitrogen (N2)
Processes:
Ammonification
Assimilation by Plants
Denitrification
Nitrification
Nitrogen fixation
Compounds:
Atmospheric Nitrogen (N2)
Ammonium (NH4+)
Nitrate (NO3-)
Nitrogen Cycle
Complete the diagram.
Atmospheric nitrogen (N2)
17.
16.
Nitrogen Fixation
Nitrate (NO3-)
Ammonification
15.
Nitrogen Fixation
Ammoniuim (NH4+)

17. Atmospheric nitrogen (N2)
Processes:
Ammonification
Assimilation by Plants
Denitrification
Nitrification
Nitrogen fixation
Compounds:
Atmospheric Nitrogen (N2)
Ammonium (NH4+)
Nitrate (NO3-)
Nitrogen Cycle
Complete the diagram.
Atmospheric nitrogen (N2)
17.
16.
Nitrogen Fixation
Nitrate (NO3-)
Ammonification
Nitrification
Nitrogen Fixation
Ammoniuim (NH4+)

18. Atmospheric nitrogen (N2) Assimilation by plants
Processes:
Ammonification
Assimilation by Plants
Denitrification
Nitrification
Nitrogen fixation
Compounds:
Atmospheric Nitrogen (N2)
Ammonium (NH4+)
Nitrate (NO3-)
Nitrogen Cycle
Complete the diagram.
Atmospheric nitrogen (N2)
17.
Assimilation by plants
Nitrogen Fixation
Nitrate (NO3-)
Ammonification
Nitrification
Nitrogen Fixation
Ammoniuim (NH4+)

19. Atmospheric nitrogen (N2) Assimilation by plants
Processes:
Ammonification
Assimilation by Plants
Denitrification
Nitrification
Nitrogen fixation
Compounds:
Atmospheric Nitrogen (N2)
Ammonium (NH4+)
Nitrate (NO3-)
Nitrogen Cycle
Complete the diagram.
Atmospheric nitrogen (N2)
Denitrification
Assimilation by plants
Nitrogen Fixation
Nitrate (NO3-)
Ammonification
Nitrification
Nitrogen Fixation
Ammoniuim (NH4+)

20. Nitrogen Cycle Nitrogen (N2)
During __________________, nitrogen gas (N2) from the ________________ is converted by soil microbes into ammonia (NH3). Other soil bacteria convert ammonia (NH3) and ammonium (NH4+) into nitrates (NO3-) using a process called ________________. Completing the cycle, soil bacteria use the process of _________________ to convert ________________ back into nitrogen gas (N2). 18 19 20 21 22

21. Nitrogen Cycle Nitrogen (N2)
During __________________, nitrogen gas (N2) from the ________________ is converted by soil microbes into ammonia (NH3). Other soil bacteria convert ammonia (NH3) and ammonium (NH4+) into nitrates (NO3-) using a process called ________________. Completing the cycle, soil bacteria use the process of _________________ to convert ________________ back into nitrogen gas (N2).
nitrogen fixation 19 20 21 22

22. Nitrogen Cycle Nitrogen (N2)
During __________________, nitrogen gas (N2) from the ________________ is converted by soil microbes into ammonia (NH3). Other soil bacteria convert ammonia (NH3) and ammonium (NH4+) into nitrates (NO3-) using a process called ________________. Completing the cycle, soil bacteria use the process of _________________ to convert ________________ back into nitrogen gas (N2).
nitrogen fixation
atmosphere 20 21 22

23. Nitrogen Cycle Nitrogen (N2)
During __________________, nitrogen gas (N2) from the ________________ is converted by soil microbes into ammonia (NH3). Other soil bacteria convert ammonia (NH3) and ammonium (NH4+) into nitrates (NO3-) using a process called ________________. Completing the cycle, soil bacteria use the process of _________________ to convert ________________ back into nitrogen gas (N2).
nitrogen fixation
atmosphere
nitrification 21 22

24. Nitrogen Cycle Nitrogen (N2)
During __________________, nitrogen gas (N2) from the ________________ is converted by soil microbes into ammonia (NH3). Other soil bacteria convert ammonia (NH3) and ammonium (NH4+) into nitrates (NO3-) using a process called ________________. Completing the cycle, soil bacteria use the process of _________________ to convert ________________ back into nitrogen gas (N2).
nitrogen fixation
atmosphere
nitrification
denitrification 22

25. Nitrogen Cycle Nitrogen (N2)
During __________________, nitrogen gas (N2) from the ________________ is converted by soil microbes into ammonia (NH3). Other soil bacteria convert ammonia (NH3) and ammonium (NH4+) into nitrates (NO3-) using a process called ________________. Completing the cycle, soil bacteria use the process of _________________ to convert ________________ back into nitrogen gas (N2).
nitrogen fixation
atmosphere
nitrification
denitrification
Nitrates (NO3-)

26. Nitrogen Cycle
23. The burning of fossil fuels releases acidic gases like sulfur dioxide (SO2) and nitrogen oxides (NOx). When these acidic gases dissolve in rainwater, __________________ forms, which kills plant life, pollutes rivers and streams, and erodes stonework.
acid rain

27. Nitrogen Cycle
24. When nitrates (NO3-) and other nutrients leach into ponds and lakes, excessive plant growth like algal blooms may result, resulting in fish kills. This condition is called
a. Eutrophication
b. Ammonification
c. Nitrogen fixation
d. De-nitrification