7
Moving Through the Carbon Cycle
C
arbon is essential for life on Earth. As you saw in Activity 6, ”Energy
Flow through an Ecosystem,” carbon-containing molecules such as
sugars and proteins are passed from one organism to the next in a food web.
On Earth, carbon can be found in many places, including in organisms,
the atmosphere, oceans and water, rocks and soil on Earth’s crust, and fossil
fuels under Earth’s surface. Each of these locations serves as a reservoir.
Think of a reservoir as a container that holds carbon-containing molecules
in one of many forms. As organisms interact in ecosystems and as geological
processes occur, carbon flows from one reservoir to the next.
In this activity you will model the pathways that the carbon takes as it flows
from one reservoir to another. You will consider how human events can
impact the carbon cycle.
CHALLENGE
How does human activity effect the movement of carbon through the
carbon cycle?
MATERIALS
For each student
1
model carbon atom
1
Student Sheet 7.1, “Moving Carbon Through the
Carbon Cycle”
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Activity 7 • Moving Through the Carbon Cycle
PROCEDURE
1. With your partner discuss your ideas about where on Earth carbon is
present and how it flows in the carbon cycle. Share your ideas with the
class.
2. On Earth, carbon can be found in several different carbon-containing
compounds. With the class make a list of molecules that contain
carbon, such as carbon dioxide (CO2).
3. The class will model the flow of carbon atoms between reservoirs on
Earth. Your teacher will assign you a role and a starting reservoir. Listen
as your teacher explains how the walking model will run.
4. When your teacher tells you to begin, move to your starting reservoir.
When it is your turn to move:
a. Select a card from the deck. The card will provide directions
describing what will happen to the carbon.
b. On Student Sheet 7.1, record the amount of carbon you will move.
c. Return the card to the bottom of the deck.
d. Take the indicated number of carbon molecules and move as
directed by the card.
e. Repeat steps a–d until your teacher directs you to stop.
5. Your teacher will give you Student Sheet 7.2, “Carbon Cycle Diagram.”
On Student Sheet 7.2, each reservoir is noted with an “X.” With the
class, locate and label each reservoir shown in the list below.
Note: You may use the labels more than once.
Carbon Reservoirs on Earth
Atmosphere
Organisms (humans, plants, animals)
Rocks and soil
Water (lakes, oceans, rivers)
Fossil fuels
6. Record the pathways you used to move carbon on Student Sheet 7.2,
“Carbon Cycle Diagram,” using the information you recorded on
Student Sheet 7.1. To do this, draw an arrow from one reservoir to the
next to show where you moved carbon.
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Moving Through the Carbon Cycle • Activity 7
7. Compare your carbon pathway on Student Sheet 7.2 to those of your
group. In what ways are they similar? In what ways are they different?
Record this at the bottom of Student sheet 7.2.
8. In your science notebook construct a table as shown below.
Human Impacts on the Carbon Cycle
Description of
Human Event
Short Term Impacts
on Carbon Flow
Long Term Impacts
on Carbon Flow
9. Your teacher will provide your group with a set of Human Impact
Cards. With your group select and read a card. Discuss the short-term
and long-term impacts the event might have on the carbon cycle.
Record these in your table. Be sure to describe how specific reservoirs
may be affected.
10. Repeat Procedure Step 8 for the remaining Human Impact Cards.
ANALYSIS
1. Based on the information on Transparency 7.2, what can you say
about the total amount of carbon in the carbon cycle?
2. Describe how the carbon contained in a catfish can end up in a blade
of grass.
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Activity 7 • Moving Through the Carbon Cycle
3. Below is a diagram of the nitrogen cycle. Use the diagram to help you
answer the following questions:
THE NITROGEN CYCLE
emissions from industrial sources
and engine combustion
Nitrogen in atmosphere (N2)
nitrogenfixation
denitrification
animals eat
plant proteins
excretion
fertilizer used in
farms and gardens
dead animals and plants
nitrifying algae
decomposers
on and in soil
blue green algae
eaten by fish
nitrogen-fixing
bacteria in roots
bacteria
nitrogen-fixing
bacteria in soil
ammonification
Nitrogen in soil
ammonium (NH4+)
nitrates (N03-)
nitrites (N02-)
ammonia (NH3)
2900 SEPUP SGI Field Test SE
Figure: SGI SE 07.01
LegacySansMedium 10/11.5
fungi
denitrifying
bacteria in soil
decaying
organic matter
decomposers in water and
soil (bacteria and fungi)
a. What forms of nitrogen do you see in the diagram?
b. Which organisms take in nitrogen-containing compounds?
c. Which organisms give off nitrogen-containing compounds?
d. Compare and contrast the carbon and nitrogen cycles.
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Moving Through the Carbon Cycle • Activity 7
4. How can human activity affect the flow of carbon through the carbon
cycle? Include an example from this activity to support your answer.
5. How has human use of fossil fuels impacted the global carbon cycle?
6. An algal bloom is an event in a marine ecosystem that can occur when
the level of nutrients in an ocean ecosystem rises. The increase in nutrient levels increases the carrying capacity of the ecosystem for algae and
the algae population increases dramatically. Describe how a change
in the algae population might impact the local carbon cycle in that
ecosystem.
7. Explain how a person’s carbon footprint relates to the carbon cycle.
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