The Carbon Cycle Molecules on the Move. The Carbon Atom All living organisms are based on the carbon atom. All living organisms are based on the carbon

The Carbon CycleThe Carbon Cycle

Molecules on the MoveMolecules on the Move

The Carbon AtomThe Carbon Atom

All living All living organisms are organisms are based on the based on the carbon atomcarbon atom. .

The Carbon AtomThe Carbon Atom

Carbon compounds can be solid, liquid, Carbon compounds can be solid, liquid, or gas under conditions commonly or gas under conditions commonly found on the earth's surface. found on the earth's surface.

Because of this, carbon can help form Because of this, carbon can help form solid minerals (such as limestone), solid minerals (such as limestone), 'squishy' organisms (such as plants and 'squishy' organisms (such as plants and animals), and can be dissolved in water animals), and can be dissolved in water or carried around the world through or carried around the world through the atmosphere as carbon dioxide gas. the atmosphere as carbon dioxide gas.

Carbon . . . On the move!Carbon . . . On the move!

Carbon atoms Carbon atoms continually move continually move through living through living organisms, the organisms, the oceans, the oceans, the atmosphere, and atmosphere, and the crust of the the crust of the planet. planet.


This movement is known as the This movement is known as the carbon cycle. The paths taken by carbon cycle. The paths taken by carbon atoms through this cycle are carbon atoms through this cycle are extremely complex, and may take extremely complex, and may take millions of years to come full circle. millions of years to come full circle.

Consider, for example, the journey of a "typical" Consider, for example, the journey of a "typical" carbon atom that existed in the atmosphere as carbon atom that existed in the atmosphere as part of a carbon dioxide molecule some 360 part of a carbon dioxide molecule some 360 million years ago, during the Carboniferous million years ago, during the Carboniferous Period. That molecule drifted into the leaf of a Period. That molecule drifted into the leaf of a large fern growing in the extensive tropical large fern growing in the extensive tropical swamp forests of that time. swamp forests of that time.

PhotosynthesisPhotosynthesis

Through Through photosynthesis, the photosynthesis, the oxygen from the oxygen from the molecule was molecule was released back into released back into the air and the the air and the carbon atom was carbon atom was removed from the removed from the molecule and used molecule and used to build a molecule to build a molecule of sugar.of sugar.

Carbon . . . Plant CellsCarbon . . . Plant Cells

The sugar could have The sugar could have been broken down by been broken down by the plant at a later the plant at a later time to release the time to release the energy stored inside, energy stored inside, but this particular but this particular sugar molecule was sugar molecule was transformed instead transformed instead into a long-lived into a long-lived structural part of one structural part of one of the plant cells. of the plant cells.

SwampSwamp Soon after, the fern Soon after, the fern

died and the remains died and the remains sank into the muck at sank into the muck at the bottom of the the bottom of the swamp. swamp.

Over thousands of Over thousands of years, more plants years, more plants grew in the swamp grew in the swamp and their remains also and their remains also sank into the swamp, sank into the swamp, forming a layer of forming a layer of dead plant material dead plant material many meters thick.many meters thick.

Swamp … to … RockSwamp … to … Rock

Gradually, the climate changed, Gradually, the climate changed, becoming drier and less tropical. becoming drier and less tropical.

Sand, dust, and other materials Sand, dust, and other materials slowly covered the ancient swamp slowly covered the ancient swamp and sealed the decaying vegetation and sealed the decaying vegetation under an ever-thickening layer of under an ever-thickening layer of sediment. sediment.

The sediment hardened, turning to The sediment hardened, turning to sedimentary rock. sedimentary rock.

Coal = Organic Coal = Organic Sedimentary RockSedimentary Rock

The carbon atom The carbon atom stayed trapped in stayed trapped in the remains of the the remains of the long-vanished long-vanished swamp while the swamp while the pressure of the pressure of the layers above slowly layers above slowly turned the turned the material into coals.material into coals.

Some 360 million years later, in the 1900s, Some 360 million years later, in the 1900s, the coal bed was mined by humans and the coal bed was mined by humans and burned to fuel industrial civilization. burned to fuel industrial civilization.

Release of EnergyRelease of Energy

The process of The process of burning released burning released the energy stored the energy stored in the carbon in the carbon compounds in the compounds in the coal and reunited coal and reunited the carbon atom the carbon atom with oxygen to with oxygen to form again form again

The Journey ContinuesThe Journey Continues

The carbon was released to the The carbon was released to the atmosphere through the smokestack atmosphere through the smokestack and the journey continues. and the journey continues.

Many other paths are possible, some Many other paths are possible, some taking only hours or days to trace, taking only hours or days to trace, others, like the one we just learned others, like the one we just learned about, many millions of years about, many millions of years


Carbon may be stored for extended Carbon may be stored for extended periods (the "sinks")periods (the "sinks")

There are various way it is likely to be There are various way it is likely to be released to the atmosphere (the released to the atmosphere (the "source")"source")

There are things that trigger these There are things that trigger these sources to release carbon (the "release sources to release carbon (the "release agents")agents")

Together they define Together they define the carbon cyclethe carbon cycle..

““The Sinks” = Where Carbon The Sinks” = Where Carbon is Storedis Stored

Carbon sinksCarbon sinks include long-lived trees include long-lived trees

““The Sinks”The Sinks”

All living All living and non-and non-living living organisorganismsms


Limestone (formed Limestone (formed from the carbon-from the carbon-containing shells of containing shells of small sea creatures small sea creatures that settle to the that settle to the ocean bottoms and ocean bottoms and build up into thick build up into thick deposits)deposits)


Plastic (a modern invention, but very Plastic (a modern invention, but very long-lived)long-lived)


And . . .And . . .

Burial of organic Burial of organic matter (such as matter (such as those that formed those that formed the fossil fuels we the fossil fuels we use today).use today).

““The Sources” = How The Sources” = How Carbon is Released into the Carbon is Released into the

AtmosphereAtmosphere Carbon sourcesCarbon sources include the burning of include the burning of

fossil fuels and other organic matterfossil fuels and other organic matter

““The Sources”The Sources”

Weathering of limestone rocksWeathering of limestone rocks


The breakdown of The breakdown of substances into simpler substances into simpler molecules is called molecules is called decompositiondecomposition..

Fungi and bacteria Fungi and bacteria decompose organic decompose organic matter.matter.

Carbon dioxide and Carbon dioxide and water are returned to water are returned to the environment.the environment.


And . . .And . . .

The respiration of The respiration of living organisms. living organisms.

(Cellular (Cellular Respiration)Respiration)

““Releasing Agents”Releasing Agents”

Release agentsRelease agents include volcanic activity, include volcanic activity, forest firesforest fires


CombustionCombustion is the is the process of burning process of burning a substance, such a substance, such as wood or fossil as wood or fossil fuels.fuels.

Because of Because of combustioncombustion, , carbon dioxide is carbon dioxide is released back into released back into the atmosphere.the atmosphere.


And . . .And . . .

Many human activities.Many human activities.

Wait!? There’s More!Wait!? There’s More!

Stay tuned for Stay tuned for more information more information about the Carbon about the Carbon Cycle!Cycle!

Please turn to page Please turn to page 509 of your 509 of your Science book.Science book.

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The Carbon Cycle Molecules on the Move. The Carbon Atom All living organisms are based on the carbon atom. All living organisms are based on the carbon