THE CARBON CYCLE CHAPTER 2.5

THE CARBON CYCLE Carbon is found in two kinds of substances: Organic Inorganic

ORGANIC SUBSTANCES Always contain atoms of carbon and hydrogen and often contain oxygen and nitrogen atoms. EXAMPLES: Proteins, sugars, and fats

INORGANIC SUBSTANCES Matter that doesn’t contain a combination of carbon and hydrogen atoms EXAMPLES: carbon dioxide (CO2), water (H2O), and ammonia (NH3)

CYCLING OF ORGANIC MATTER The materials used in building the bodies of living organisms are limited to the atoms and molecules that make up the planet. To maintain life on Earth, matter must be recycled. Every carbon atom is recycled time and time again into new life forms.

THE CARBON CYCLE Carbon is an element Carbon atoms are the basis for all living things (called organic matter) and for all matter that was once living (called detritus)

Carbon is stored in FOUR places: Living things The atmosphere The ocean The earth’s crust These storage places are called carbon sinks.

How does carbon cycle? Carbon is removed from the atmosphere by plants when they photosynthesize to make sugar. Photosynthesis Reactants Products 6CO2 + 6H2O + light → C6H12O6 +6O2 Carbon Dioxide + water + light → Sugar (Glucose) + oxygen Making Molasses

Please fill in chart on page 62. Carbon is returned to the atmosphere by plants and by animals when they exhale. Respiration Reactants Products C6H12O6 + O2 → CO2 + H2O Sugar + oxygen → carbon dioxide + water Please fill in chart on page 62.

Photosynthesis and cellular respiration are complementary processes. The carbon that they use is repeatedly cycled through both processes. This process is often called the CARBON CYCLE.

Decay or Fossil Fuels Most of the carbon that forms living organisms is released to the atmosphere or water as carbon dioxide from dead decaying organisms. Under certain conditions the decay process is delayed, and the organic matter may be converted into rock or fossil fuels such as coal, petroleum and natural gas.

This carbon is not released until the combustion process takes place through burning the fuels.

Reservoirs for Inorganic Carbon When not in organic form, carbon can be found in three main reservoirs (Reservoirs are storage areas): Atmosphere Oceans The Earth’s crust

The Ocean Carbon is found in sea shells and bones. When these fall to the bottom of the oceans and get covered with sediment, they decompose over millions of years to form oil (one of the fossil fuels).

(Millions of tonnes of soil) Shells and Bones Sink to the bottom of the ocean Covered by sediment (Millions of years) Form oil (example: Offshore drilling NFLD)

Reservoirs for Organic Carbon Organic carbon is also held in reservoirs – the bodies of living things. All living things die and decomposition eventually returns the carbon to the cycle in inorganic form.

One Important Exception Bogs – store huge quantities of carbon in organic form Bogs have very little oxygen, therefore decomposition is very slow Carbon atoms may remain locked away in dead plant matter (peat) for many years in a bog. When plants die in a bog, they form peat that can get trapped under sediments and potentially form coal (another form of fossil fuel) video

Bog Formation