Cycles - WEB Practice
Multiple Choice
Identify the choice that best completes the statement or answers the question.
____
____
____
1. Which process describes nitrogen fixation?
a. animals eat plants containing nitrogen and return it to the soil through urination
b. bacteria take nitrogen from the air and convert it to a form usable by plants
c. organisms die and are decomposed into ammonia in the soil
d. plants take nitrogen from the air and store it in their roots
2. Which cycle is least dependent on biotic processes?
a. carbon
c. phosphorus
b. nitrogen
d. water
3. One of the nutrient cycles moves from an atmospheric gaseous form to the soil through both abiotic and
biotic processes, moves through the food web, then is returned to the soil or to the atmosphere. Which
cycle fits this description?
a. carbon
c. phosphorus
b. nitrogen
d. water
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4. Which of the following is the process by which gaseous water becomes liquid water?
a. transpiration
c. evaporation
b. respiration
d. condensation
Completion
Complete each statement.
5. Burning fossil fuels has rapidly released long-term reserves of the ____________________ cycle.
6. A nitrogen molecule has just been “fixed” by a nitrogen-fixing bacterium. The next organism to use the
nitrogen molecule is probably a(n) __________________.
7. Plants return liquid water to the atmosphere through a process called ____________________.
8. How does carbon get back into the carbon cycle from the food that we eat?
9. From what molecule do trees get their carbon?
10. Besides nitrogen fixing bacteria, what else can break the strong triple bond between the two
nitrogen atoms in nitrogen gas?
Short Answer
11. Compare and contrast the ways carbon and water cycle through the biosphere.
Figure 3–3
12. Explain how seepage and transpiration in Figure 3-3 are related.
Essay
13. Describe the roles of bacteria in the nitrogen cycle.
14. If nitrogen makes up over 70% of the atmosphere in which we live, why is nitrogen a limiting
factor for plants?
15. Compare and contrast nitrifying bacteria and denitrifying bacteria.
Cycles - WEB Practice
Answer Section
MULTIPLE CHOICE
1. ANS: B
Nitrogen fixation is performed by specialized bacteria that convert nitrogen gas into ammonia.
Feedback
A
B
C
D
This happens during the nitrogen cycle, but it is not called fixation.
That's correct!
Check page 48.
You're on the right track.
PTS: 1
NAT: LS_4a
2. ANS: D
DIF: Bloom's Level B
STA: III.5.5
TOP: 2-7
REF: 48
The water cycle is largely dependent on abiotic processes such as evaporation.
Feedback
A
B
C
D
A key component of the carbon cycle is the release of carbon dioxide during cellular
respiration.
Check the definition of nitrogen fixation.
Decomposers are important in the phosphorus cycle.
That's correct!
PTS: 1
NAT: LS_4a
3. ANS: B
DIF: Bloom's Level D
STA: III.5.5
TOP: 2-9
REF: 46–49
Nitrogen is the only nutrient that goes into the soil through both biotic (nitrogen-fixing bacteria) and abiotic
(lightning) processes.
Feedback
A
B
C
D
Carbon dioxide is taken up by plants directly from the atmosphere.
That's correct!
Review the phosphorus cycle on page 49.
How does water get out of the atmosphere?
PTS: 1
NAT: LS_4a
4. ANS: D
COMPLETION
5. ANS:
carbon
DIF: Bloom's Level D
STA: III.5.5
TOP: 2-9
PTS: 1
REF: 45–49
Petroleum and coal are long-term storage reserves of carbon that are being released rapidly by burning
them.
PTS: 1
DIF:
NAT: LS_4a | LS_4e
6. ANS:
Bloom's Level C
STA: III.5.5
REF: 47
TOP: 2-7
plant
Nitrogen-fixing bacteria often live in close association with plants, who benefit from the usable nitrogenous
compounds the bacteria produce.
PTS: 1
NAT: LS_4a
7. ANS:
DIF: Bloom's Level C
STA: III.5.5
TOP: 2-7
REF: 48
transpiration
Plants draw water from the ground through their roots and release it through their stomata as water vapor.
PTS: 1
DIF: Bloom's Level B
NAT: LS_4a
STA: III.5.5
TOP: 2-7
8. ANS: Breathing - more spefically it is cellular respiration.
REF: 46
PTS: 1
9. ANS: Carbon dioxide
PTS: 1
10. ANS: LIGHTNING!!!!!
PTS:
1
SHORT ANSWER
11. ANS:
Answers will vary but should include that both carbon and water are found together in the biotic parts of the
biosphere. The major reservoir for carbon is the atmosphere and oceans, while the major reservoir for water
is the oceans. Students may describe or draw the water and carbon cycles.
PTS: 1
NAT: LS_4a
12. ANS:
DIF: Bloom's Level B
STA: III.5.5
TOP: 2-9
REF: 45–47
Water seeps through soil and into the ground water. Roots of trees and plants take the water up through
their roots. Plants release the water through the process of transpiration. Both seepage and transpiration are
parts of the water cycle.
PTS:
ESSAY
1
REF: p. 75
13. ANS:
Certain types of bacteria are able to use nitrogen gas directly. These bacteria, which live in the soil and on
the roots of legumes, convert nitrogen gas to ammonia during the process of nitrogen fixation. Other
bacteria in the soil convert ammonia into nitrates and nitrites, which are also taken up directly by producers.
Still other soil bacteria convert nitrates into nitrogen gas during the process of denitrification, returning the
nitrogen to the atmosphere.
PTS: 1
REF: p. 78
14. ANS:
The nitrogen in the air is not in a usable form for most plants. The specialized bacteria have the
ability to break apart the nitrogen gas and put it in a usable form for plants.
PTS: 1
15. ANS:
Both nitrifying bacteria and denitrifying bacteria are found in the soil and also are both changing
the form in which the nitrogen exists. The nitrogen fixing bacteria, however, changes nitrogen gas
into a usable form (NH3). While denitrifying bacteria change a usable form of nitrogen (NO3) into
nitrogen gas (N2).
PTS:
1