Carbon Cycle
• The carbon cycle is the biogeochemical cycle
by which carbon is exchanged between the
biosphere and living organisms.
• Carbon is an essential component of proteins,
fats and carbohydrates which make up all
LIVING ORGANISMS.
Carbon Cycle
Important Vocabulary
– Cellular Respiration
– Photosynthesis
– Decomposition
– Combustion
– Fossil Fuels
• Coal
• Oil
• Natural Gas
Carbon Cycle
• Carbon exists in the Earth's atmosphere primarily as
the gas carbon dioxide (CO2).
• Carbon is taken from the atmosphere and returned
to the Earth by the process of PHOTOSYNTHESIS.
• Carbon can be released back into the atmosphere in
many different ways, including:
– Cellular Respiration
– Decomposition
– Combustion
Photosynthesis
• Remember Photosynthesis?
– Plants take carbon dioxide from
the atmosphere, combine it with
light energy and water to
produce glucose and oxygen.
CO2 + H2O + light energy → C6H12O6 + O2
(carbon dioxide) + (water) + light energy → (glucose) + (oxygen)
Cellular Respiration
• Remember Cellular Respiration?
• Cellular Respiration, performed by BOTH plants and animals,
involves the breaking down of glucose into carbon dioxide and
water.
C6H12O6 + O2 → CO2 + H2O
(glucose) + (oxygen) → (carbon dioxide) + (water)
• The Carbon Dioxide is then released back into the
atmosphere.
Decomposition
• Carbon is returned to the earth and released
into the atmosphere through the decay of
plants and animals.
• Decomposers, such as fungi and bacteria,
break down the carbon compounds in dead
animals and plants and convert the carbon
into carbon dioxide in the presence of oxygen,
or methane if oxygen is not present.
Combustion
• Combustion is the burning of
fossil fuels such as coal, oil,
and natural gas. Combustion
releases carbon that has been
stored in the Earth’s crust for
millions of years into the
atmosphere as carbon
dioxide.
Interesting Scientific Fact:
• When some prehistoric plants and
animals died, they became buried
over time by layers of Earth.
During that time, they were
changed into fossil fuels such as
coal, oil, and natural gas. The
carbon contained in those once
living organisms is burned as a
fuel for cars. That same carbon is
then released into the
atmosphere.
Humans Affects
on the Carbon Cycle
• Combustion (burning fossil fuels)
– Driving their cars A LOT!
• Deforestation (destroying vegetation that
absorbs carbon dioxide)
REMEMBER THIS!!!
• Carbon enters the atmosphere through
cellular respiration, decomposition, and
combustion.
• Carbon is absorbed from the atmosphere
through photosynthesis.
• Humans have GREATLY impacted the carbon
cycle by putting more carbon dioxide into the
atmosphere through combustion than what
is removed by photosynthesis!
Carbon Cycle Summary
• Now you have learned
about the carbon cycle,
check out the:
Carbon Cycle Animation
Questions???
Question 4: How does carbon enter the atmosphere?
Question 5: How is carbon removed from the atmosphere?
Question 6: How does carbon enter living organisms?
Question 7: How are humans impacting the carbon cycle and what is one of
the results from human impact?