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The Carbon Cycle
Background:
Carbon is an extremely common element on earth and can be found in
all four major spheres of the planet: biosphere, atmosphere, hydrosphere, and
lithosphere. Carbon is part of both the living and non-living parts of the planet,
as a component in organisms, atmospheric gases, water, and rocks. The carbon
contained in any of the planet’s spheres does not remain there forever. Instead,
it moves from one sphere to another in an ongoing process known as the
carbon cycle. The carbon cycle is extremely important on earth as it influences
crucial life processes such as photosynthesis and respiration, contributes to fossil fuel formation, and impacts
the earth’s climate.
The amount of carbon on the planet is stable. But, the amount of carbon in any given sphere of the
planet can increase or decrease depending on the fluctuations of the carbon cycle. The cycle can be thought of
in terms of reservoirs (places where carbon is stored) and flows (the movement between reservoirs). The
atmosphere, the biosphere, the hydrosphere, and the lithosphere are the reservoirs and the processes by which
carbon moves from one reservoir to another are the flows. Pure carbon is not common. Rather, carbon is usually
bound to other elements in compounds. Thus, when carbon moves or cycles, it is usually doing so within
compounds, such as carbon dioxide and methane. There are natural fluctuations in the carbon cycle, but humans
have been changing the carbon flows on earth at an unnatural rate.
In this activity, students will:
1. learn that carbon is in all four of the earth’s major spheres: biosphere, hydrosphere, atmosphere, and
lithosphere.
2. understand that carbon moves/cycles from one sphere to another.
3. understand how humans influence the carbon cycle and contribute to global climate change.
Introduction questions:
1. Define biogeochemical cycle
2. For the following four words. A sphere refers to the parts of the plante. Look at each root word and use
outside knowledge to predict what area(s) of Earth is contained in each sphere.
Sphere
Prediction
Definition
Biosphere
Lithosphere
Hydrosphere
Atmosphere
3. Practice with the water cycle: The water cycle move H2O throughout all four spheres. Try to draw as
many arrows explaining how water may move from one sphere to another. One is completed for you.
ATMOSPHERE
HYDROSPHERE
BIOSPHERE
LITHOSPHERE
With your Group:
There are “sphere cards” that each represents a sphere on earth at your table. Arrange them in the order
shown in the question above. There are also 9 arrows at your table that show the major processes that move carbon
from one sphere to another during the carbon cycle.
Your goal:
1. With your group, start by predicting what each process might mean.
a. Respiration:
b. Photosynthesis:
c. Diffusion:
d. Burial and Sedimentation:
e. Weathering and Erosion:
f. Eruption of gasses:
2. Place the arrows between the appropriate sphere cards and facing the appropriate direction on your table.
3. When you think you have the correct definitions and arrow arrangement, have your teacher check you off.
4. Copy your diagram on your table onto the next page.
5. You teacher will give you set different ways humans can alter the carbon cycle. Define each below:
Deforestation in the
Burning fossil fuels in
Farming rice
Capture and store carbon
amazon
automobiles
in geological formations
Planting new trees
Framing cattle
Burning fossil fuels for
electricity
Increased cement
manufacturing for dams
6. Place each of these human impact arrows in a way you think they will move carbon throughout the cycle, check
with your teacher, and copy it onto your diagram.
7. Answer the analysis questions on your own and then move onto the next activity.
The Carbon Cycle
Read the following and answer the analysis questions.
Initial impacts of a human alteration to the carbon cycle might be a flux from one sphere to another sphere, but
that that initial flux might cause other movements in the cycle too. It is a carbon cycle after all and what moves
into one sphere will eventually move into other spheres. Parts of the cycle move at different speeds and that
some movements between spheres happen relatively quickly while others take a really long time.
Analysis:
1. What are the four spheres?
2. Circle which of the following add carbon to the atmosphere?
Human Impacts
Respiration
Photosynthesis
Diffusion
Burial and Sedimentation
Weathering and Erosion
Eruption of gasses
3. Which of the following remove carbon from the atmosphere?
Human impacts
Respiration
Photosynthesis
Diffusion
Burial and Sedimentation
Weathering and Erosion
Eruption of gasses
4. Why do we worry about carbon levels in the atmosphere?
5. Are humans adding more carbon to the carbon cycle?
6. What are humans doing to change the carbon cycle?
7. Which of these human alterations to the carbon cycle a problem? Why?
8. Which of these human alterations to the carbon cycle are good? Why?
9. What can humans do to decrease the amount of carbon being released into the atmosphere?