ZURICH INTERNATIONAL SCHOOL
Coordinated Science I
Name________________________________
Date____________
Review: Carbon Cycle
1. Carbon is one of the most important elements for living things.
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All living organisms are made of molecules that contain carbon (like proteins, carbohydrates, lipids, and
nucleic acids).
In a process that is critical to life on Earth, plants take in carbon dioxide in order to carry out photosynthesis:
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Additionally we all produce carbon dioxide (CO2) as waste from cellular respiration:
2. Why is carbon such an important element? Draw its Lewis dot structure. What do you notice about the number of
bonds that it is able to make?
3. The image below shows the carbon cycle. Based on what you see in the image, what does it mean for an element
to cycle through the environment?
a. Each organism in the cycle must have an "in" arrow as well as an "out" arrow. Why?
4. All of the arrows represent processes that lead to the movement of carbon. Match the following processes to their
definitions. Also, where space is provided record the balanced chemical equations for the reactions (you may have to
research some online).
Processes
_____ Photosynthesis
Chemical equation:
_____________________________________
Definitions
a. Reaction that happens in basically all cells on Earth. Breaks
up sugars and stores their energy in ATP, the molecule that all
cells use for energy.
_____ Consumption
b. The process of burning something. The rapid chemical
combination of a substance with oxygen, involving the rapid
release of energy from the substance.
_____ Cell respiration
Chemical equation:
____________________________________
_____ Death
c. To make a solution by mixing with a liquid.
d. When an organism cannot make its own sugars, it eats the
tissues of another living (or recently living) organism.
_____ Rock & fossil formation
_____ Combustion
Chemical equation:
CH4 + O2  ______________________
_____Dissolution of CO2 in water
Chemical equation:
____________________ H2CO3
e. When organism dies and is buried in the right conditions (not
much weathering, no decomposers), parts of the organism can
undergo a series of chemical reactions over loooong periods of
time. Ultimately the tissues are replaced by rock-like minerals.
f. The end of the life of an organism.
g. The process by which green plants and some other
organisms (like marine phytoplankton) use sunlight to make
sugars from carbon dioxide and water.
5. Intake versus release of CO2
a. Examine the carbon cycle diagram. List the processes
that lead to the release of CO2 into the atmosphere.
b. Examine the carbon cycle diagram. List the processes
that lead to the intake of CO2 from the atmosphere.
c. Which type of process is there less of: release or intake? __________________
d. On the carbon cycle diagram on the previous page, color all of your down arrows so that this point will be
obvious.
6. Based on the carbon cycle diagram, explain how the following human activities have affected the carbon cycle:
a. Combusting (burning) fossil fuels
b. Cutting down forests to use as firewood or to clear land for grazing animals
c. Planting trees