THE CARBON CYCLE
What Is Carbon?
 An element
 The basis of life of earth
 Found in rocks, oceans, atmosphere, and all living
organisms.
Carbon Cycle
 The same carbon atoms are used repeatedly on earth.
They cycle between the earth and the atmosphere.
Plants Use Carbon Dioxide
 Plants pull carbon dioxide (CO2) from the atmosphere.
 Using sunlight with the CO2 they make glucose.
 This process is photosynthesis.
 The carbon can be used by the plant (food) and used to
build the plant (cellulose).
 Also gives off CO2 from cellular respiration.
Animals Eat Plants
 When organisms eat plants, they take in the carbon
and some of it becomes part of their own bodies.
 They generate CO2 from cellular respiration(break
down of glucose) and exhale this CO2 into the
atmosphere.
Animals Eat Animals
 When organisms eat animals, they take in the carbon
and some of it becomes part of their own bodies.
 They generate CO2 from cellular respiration (break
down of glucose) and exhale this CO2 into the
atmosphere.
Plants and Animal Die
 When plants and animals die, most of their bodies are
decomposed and carbon atoms are returned to the
atmosphere.(CO2)
 Some are not decomposed fully and end up as
deposits underground (oil, coal, etc.= fossil
fuels=Carbon)
Carbon Slowly Returns to Atmosphere
 Carbon in rocks and underground deposits is released
very slowly into the atmosphere.
 This process takes many years.
Carbon in Oceans
 Additional carbon is stored in the ocean.
 CO2 passes into the water from the atmosphere.
 Plants & phytoplankton use for photosynthesis.
 Many animals pull carbon from water to use in shells,
etc.
 Animals die and carbon substances are deposited at
the bottom of the ocean.
 Oceans contain earth’s largest store of carbon.
Burning wood and Fossil
Fuels
 Releases carbon compounds in air, water, and soil
 * one gallon of gas burned in a car=19lbs of CO2 (Who
Killed the Electric Car, 2004)
Cycle – Repeats Over
and Over and Over and
Over …
Human Impact
 Fossil fuels release carbon stores very slowly
 Burning anything releases more carbon into
atmosphere — especially fossil fuels
 Increased carbon dioxide in atmosphere increases
global warming
 Fewer plants mean less CO2 removed from
atmosphere
What We Need to Do
 Burn less, especially fossil fuels
 Promote plant life, especially trees