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.

Plants Use Carbon Dioxide
Plants pull carbon dioxide from the
atmosphere and use it to make food –—
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.

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.

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 and
soil
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

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.

The Carbon Cycle

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

Carbon reservoirs

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

Respiration
CH2O + O2  CO2 + H2O + energy

Combustion or Oxidization of
hydrocarbon
CH4 + 2 O2  CO2 + 2 H2O + energy

Human Impacts on the Carbon
Cycle
Burning fossil fuels have serious impact
on the carbon cycle.

Fossil Fuel
86% of global primary energy
consumption is fossil fuels.

Fossil Fuels
• Petroleum
• Natural
Gas
• Coal

CO2
Concentration
Pre-Industrial value: 280 ppm (600 billion tons)
Current value: 380 ppm (800 billion tons)
Critical value: 560 ppm (1200 billion tons)

Organic Carbon
Hydrocarbons: CH4
Carbohydrate: CH2O

Inorganic carbon
Carbon Dioxide: CO2
Calcium Carbonate: CaCO3
Mandale Limestone Quarry

Carbon reservoirs
•The atmosphere.
•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
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