Name ______________________________________
Period ________
Carbon Cycle
Answer the questions as you go throughout the reading.
I. Industrial Revolution & Carbon
When the Industrial Revolution began around 1750, humans started to switch from farming
communities to urban cities using fossil fuel powered machinery and factories. The large scale
burning of fossil fuels released amounts of CO2 into the atmosphere that were unheard of at that
time period. Observe the graph below- notice the change in CO2 after the Industrial Revolution.
1. How did the Industrial Revolution affect the CO2 levels in the atmosphere? ____________
_______________________________________________________________________
2. Explain your answer to #1. __________________________________________________
II. Vocabulary
Carbon Sink
Anything that absorbs more CO2 than it releases into the atmosphere
Carbon Source
Anything that releases more CO2 into the atmosphere than it absorbs
Photosynthesis
Plants convert CO2, sunlight and water into sugars and Oxygen
Takes Carbon out of the atmosphere; stored in plant
Respiration
Animals break down stored Carbon based sugars and turn it into energy,
CO2 and water
Releases Carbon into the atmosphere
Name ______________________________________
Decomposition
Combustion of
fossil fuels
Volcanoes
Period ________
The decay of organisms takes Carbon out of the atmosphere and puts it
into the soil to eventually become rocks (carbonate) or fossil fuels
Burning fossil fuels releases large amounts of Carbon into the atmosphere
When they erupt, they release large amounts of Carbon into the
atmosphere
II. Carbon Sinks & Sources
Carbon can be found in atmosphere as Co2, in rocks or soil as carbonate, in fossil fuels or
living things, and dissolved in the ocean. Sources of carbon are anything that releases more
Carbon into the atmosphere than it absorbs. Carbon sources include the combustion of fossil fuels
in power plants & transportation, wildfires, deforestation, animal respiration and volcanoes- they all
release Carbon into the atmosphere. The ocean also releases some Carbon back into the
atmosphere.
Carbon sinks include anything that absorbs more Carbon than it releases. The three major
Carbon sinks include plants, the ocean and soil. Fossil fuels used to be a Carbon sink because the
Carbon stayed buried underground but once humans began mining for fossil fuels and burning
them, fossil fuels turned from a sink to a source.
A. Plants take in Carbon as CO2 from the atmosphere during photosynthesis and store it as
sugars in their cells. When the plants die, the Carbon is transferred to the soil.
B. Soil receives Carbon from the decomposition of organisms or plants. Additional Carbon
is stored in the rocks in the form of carbonate.
C. Oceans absorb CO2 from the atmosphere through the following processes:



Ocean plants like algae or small creatures called phytoplankton suck up CO2 from
the air to use in photosynthesis. When they die, the Carbon they stored in their
bodies sinks to the ocean floor.
Another option is through diffusion- the CO2 simply dissolves into the ocean. Cold
ocean water absorbs more CO2 than warm ocean water.
Finally, Carbon can be found in the ocean as Calcium Carbonate- the main
component in the hard shells of clams, oysters and coral reefs. When these
organisms die, they sink to the bottom of the ocean and create rich carbonate
deposits that eventually turn into limestone.
Name ______________________________________
Period ________
Carbon Cycle Questions:
3. Explain the difference between carbon sinks and sources. ___________________________
________________________________________________________________________
4. List 3 natural carbon sources which release Carbon into the atmosphere. _______________
________________________________________________________________________
5. List 3 anthropogenic carbon sources which release Carbon into the atmosphere. _________
_______________________________________________________________________
6. List 3 Carbon sinks which absorb Carbon. ______________________________________
7. What process do plants use to take in Carbon? ___________________________________
8. What process do animals use to release Carbon back into the atmosphere? _____________
9. What process returns Carbon from plants and animals back into the soil? _______________
10. Explain the 3 ways that the ocean absorbs Carbon.
a. _________________________________________________________
b. _________________________________________________________
c. _________________________________________________________
11. Label the diagram below using the following Word Bank.
Combustion of Fossil Fuels
Atmospheric CO2
Photosynthesis
Decomposition
Respiration