THE CARBON CYCLE

What Is Carbon?

An element

The basis of life of earth

Found in rocks, oceans, atmosphere

Carbon Cycle

The same carbon atoms are used repeatedly on earth. They cycle between the earth and the atmosphere.

Inorganic Carbon

Carbon exists in the nonliving environment as:

Carbon dioxide (CO2) Carbonic acid ( HCO3

−)

Carbonate rocks (limestone and coral = CaCO3)

Deposits of Fossil fuels Dead organic matter

Organic Carbon

Hydrocarbons: CH4

Carbohydrate: CH2O

Carbon reservoirs

Carbon reservoirs

•The atmosphere. (CO2)

•The biosphere (include fresh water systems and non-living organic material, such as soil carbon)

•The oceans (including dissolved inorganic carbon and living and non-living marine biota)

•The lithosphere (sediments, Earth core including fossil fuels)

Carbon Cycle

Carbon is released into the atmosphere in several ways

• Respiration by plants and animals.

• Decay of animal and plant matter.

• Combustion of organic material

• Production of cement.

• The ocean releases CO2 into the atmosphere. • Volcanic eruptions and metamorphism

Carbon is taken from the atmosphere in several ways

Photosynthesis. The oceans when the seawater becomes

cooler, more CO2 dissolve and become carbonic acid.

In the upper ocean areas organisms convert reduced carbon to tissues, or carbonates.

Photosynthesis

CO2 + H2O + sunlight CH2O + O2

Plants Use Carbon Dioxide

Plants pull carbon dioxide from the atmosphere and use it to make sugars through photosynthesis.

The carbon becomes part of the plant (stored food).

Animals Eat Plants

When organisms eat plants, they take in the carbon and some of it becomes part of their own bodies.

Respiration

CH2O + O2 CO2 + H2O + energy

Done by plants and animals

Combustion or Oxidization of hydrocarbon

CH4 + 2 O2 CO2 + 2 H2O + energy

Plants and Animal Die

When plants and animals die, most of their bodies are decomposed and carbon atoms are returned to the atmosphere.

Some are not decomposed fully and end up in deposits underground (oil, coal, etc.).

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.

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.

Cycle – Repeats Over and Over and Over and Over …

Carbon Cycle Diagram

Carbon in Atmosphere

Plants use carbon to make food

Animals eat plants and

take in carbon

Plants and animals die

Decomposers break down dead things,

releasing carbon to

atmosphere andsoil

Bodies not decomposed —

after many years, become part of oil or coal deposits

Fossil fuels are burned; carbon is

returned to atmosphere

Carbon slowly released from

these substances returns to

atmosphere