Carbon cycle





Carbon Cycle 2799
Photo by: Collpicto

The carbon cycle is the process in which carbon atoms are recycled over and over again on Earth. Carbon recycling takes place within Earth's biosphere and between living things and the nonliving environment. Since a continual supply of carbon is essential for all living organisms, the carbon cycle is the name given to the different processes that move carbon from one to another. The complete cycle is made up of "sources" that put carbon back into the environment and "sinks" that absorb and store carbon.

Recycling carbon

Earth's biosphere can be thought of as a sealed container into which nothing new is ever added except the energy from the Sun. Since new matter can never be created, it is essential that living things be able to reuse the existing matter again and again. For the world to work as it does, everything has to be constantly recycled. The carbon cycle is just one of several recycling processes, but it may be the most important process since carbon is known to be a basic building block of life. As the foundation atop which a huge family of chemical substances called organic substances are formed, carbon is the basis of carbohydrates, proteins, lipids, and nucleic acids—all of which form the basis of life on Earth.

Since all living things contain the element carbon, it is one of the most abundant elements on Earth. The total amount of carbon on Earth, whether we are able to measure it accurately or not, always remains the same, although the carbon regularly changes its form. A particular carbon atom located in someone's eyelash may have at one time been part of some now-extinct species, like a dinosaur. Since the dinosaur died and decomposed millions of years ago, its carbon atoms have seen many forms before ending up as part of a human being. It may have been part of several plants and trees, free-floating in the air as carbon dioxide, locked away in the shell of a sea creature and then buried at the ocean bottom, or even part of a volcanic eruption. Carbon is found in great quantities in Earth's crust, its surface waters, the atmosphere, and the mass of green plants. It is also found in many different chemical combinations, including carbon dioxide (CO 2 ) and calcium carbonate (CaCO 3 ), as well as in a huge variety of organic compounds such as hydrocarbons (like coal, petroleum, and natural gas).

Words to Know

Biosphere: The sum total of all life-forms on Earth and the interaction among those life-forms.

Decomposition: The breakdown of complex molecules—molecules of which dead organisms are composed—into simple nutrients that can be reutilized by living organisms.

Fossil fuel: A fuel such as coal, oil, or natural gas that is formed over millions of years from the remains of plants and animals.

Greenhouse effect: The warming of Earth's atmosphere due to water vapor, carbon dioxide, and other gases in the atmosphere that trap heat radiated from Earth's surface.

Hydrocarbons: Molecules composed solely of hydrogen and carbon atoms.

Photosynthesis: Chemical process by which plants containing chlorophyll use sunlight to manufacture their own food by converting carbon dioxide and water to carbohydrates, releasing oxygen as a by-product.

Respiration: The process in which oxygen is used to break down organic compounds into carbon dioxide and water.

Carbon cycle processes

If a diagram were drawn showing the different processes that move carbon from one form to another, its main processes would be photosynthesis, respiration, decomposition, natural weathering of rocks, and the combustion of fossil fuels.

Photosynthesis. Carbon exists in the atmosphere as the compound carbon dioxide. It first enters the ecological food web (the connected network of producers and consumers) when photosynthetic organisms, such as plants and certain algae, absorb carbon dioxide through tiny pores in their leaves. The plants then "fix" or capture the carbon dioxide and are able to convert it into simple sugars like glucose through the biochemical process known as photosynthesis. Plants store and use this sugar to grow and to reproduce. Thus, by their very nature as makers of their own food, plants remove carbon dioxide from the atmosphere. When plants are eaten by animals, their carbon is passed on to those animals. Since animals cannot

The carbon cycle. (Reproduced by permission of The Gale Group.)
The carbon cycle. (Reproduced by permission of
The Gale Group
.)

make their own food, they must get their carbon either directly by eating plants or indirectly by eating animals that have eaten plants.

Respiration. Respiration is the next step in the cycle, and unlike photosynthesis, it occurs in plants, animals, and even decomposers. Although we usually think only of breathing oxygen when we hear the word "respiration," it has a broader meaning that involves oxygen. To a biologist, respiration is the process in which oxygen is used to break down organic compounds into carbon dioxide (CO 2 ) and water (H 2 O). For an animal then, respiration is both taking in oxygen (and releasing carbon dioxide) and oxidizing its food (or burning it with oxygen) in order to release the energy the food contains. In both cases, carbon is returned to the atmosphere as carbon dioxide. Carbon atoms that started out as components of carbon dioxide molecules have passed through the body of living organisms and been returned to the atmosphere, ready to be recycled again.

Decomposition. Decomposition is the largest source through which carbon is returned to the atmosphere as carbon dioxide. Decomposers are microorganisms that live mostly in the soil but also in water, and which feed on the rotting remains of plants and animals. It is their job to consume both waste products and dead matter, during which they also return carbon dioxide to the atmosphere by respiration. Decomposers not only play a key role in the carbon cycle, but also break down, remove, and recycle what might be called nature's garbage.

Weathering of rocks. Not all carbon atoms are always moving somewhere in the carbon cycle. Often, many become trapped in limerock, a type of stone formed on the ocean floor by the shells of marine plankton. Sometimes after millions of years, the waters recede and the limerock is eventually exposed to the elements. When limerock is exposed to the natural process of weathering, it slowly releases the carbon atoms it contains, and they become an active part of the carbon cycle once again

Human-caused increase of carbon dioxide in the atmosphere. In recent history, humans have added to the carbon cycle by burning fossil fuels. Ever since the rapid growth of the Industrial Revolution in the nineteenth century when people first harnessed steam to power their engines, human beings have been burning carbon-containing fuels like coal and oil (called fossil fuels) for artificial power. This constant burning produces massive amounts of carbon dioxide, which are released into Earth's atmosphere. Over the last 150 years, the burning of coal, oil, and natural gas has released some 270 billion tons (245 billion metric tons) of carbon into the air in the form of carbon dioxide.

Luckily, more than half of the carbon dioxide emitted by the burning of fossil fuels is absorbed by the oceans, by plants, and by soils. Regardless, scientists feel fossil fuel consumption could be an example of a human activity that affects and possibly alters the natural processes (photosynthesis, respiration, decomposition) that nature had previously kept in balance. Many scientists believe that carbon dioxide is a "greenhouse gas." This means that it traps heat and prevents it from escaping from Earth. As a result, this trapped gas leads to a global temperature rise, a natural phenomenon known as the greenhouse effect, which can have disastrous effects on Earth's environment.

[ See also Greenhouse effect ]



User Contributions:

Sheena
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Mar 14, 2007 @ 9:21 pm
Thanks for the useful information.
send me some information about carbon cycle, carbon trading, Kyoto protocol and the greenhouse effect.
Ibrahim adam
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Apr 8, 2007 @ 1:13 pm
Thank u for the valuable information. Its a nice article. Can u send me diagrams of carboniferous rocks. I wil be hapy and will be very thankful
Ana
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May 14, 2007 @ 8:08 am
Just wanted to ley you know your diagram was easy to understant and great to study! thanks!
satish
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Aug 18, 2007 @ 2:02 am
Thanks for the info,can you provide me more info on how deforestation helps in carbon cycle. The image says a lot.
tony
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Sep 27, 2007 @ 5:17 pm
you diagram was really really easy to understand. thanks for the help. my biology teacher will be really happy!
Simon
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Sep 27, 2007 @ 7:19 pm
Your article is very understandable and the facts that it contains are well detailed. The diagram is a major help as well. Thanks alot! This will come in handy for my biology project!
emopunkgirl_cindy
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Oct 17, 2007 @ 7:19 pm
omg! thank you people this info really helped me!!!!....ahhh thanks millions! lol...i needed this for my biome powerpoint projekt!
thanks anyways!!!
awsome description and illustartion
O_o Cindy O_o //_^
joa
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Feb 7, 2008 @ 7:07 am
tnx! It really helps me on my report... The diagram is so nice that my classmates understand it easily...
Good work!
Jon
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May 7, 2008 @ 10:10 am
Thanks..very useful..needed to know the decomposers' role in the carbon cycle :)
sudheer
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Jul 5, 2008 @ 11:23 pm
Thank you very much, your information was helpful and very simple.
chels!!!!!!
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Oct 9, 2008 @ 4:04 am
great info!!!!!!!!!!! ............thanks xx. Great help with my project....... =)
ernesto
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Aug 14, 2009 @ 2:02 am
tnx.......... it wil help me 2 my project,i wish that it have also carbon dioxide to oxygen cycle.....
rebecca
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Aug 15, 2009 @ 12:00 am
what is fossilisation in the co2 cycle?
i have photosynthesis, consumption, combustion, respiration and dissolving but i dont know what process they all belong too.
just me :]
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Dec 17, 2009 @ 6:18 pm
Thank-you. Will help me with the project. You should get the carbon cycle too. lol. You guys clarify this very well. :P
ikedi kelvin ohaegbu
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Jan 20, 2010 @ 4:04 am
Thanks for your patronage and the help.Thanks alot
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Feb 22, 2010 @ 6:18 pm
You have a nice informational and thx you for provide us nice more knowledge.
Keep it up!!
Helpful
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May 8, 2010 @ 7:19 pm
Thank you so much i needed this to study for my test tomorrow, very helpful :)
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Jun 4, 2010 @ 11:23 pm
It is really a useful article and it demonstrates very clear.
Thanks.
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Nov 9, 2010 @ 9:21 pm
A+Mazing job. I didnt get it when my teacher taught us, but now pheff! i undertand its like abd's :D
shannen
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Nov 17, 2010 @ 7:07 am
i am very happy with this article as it has informed me of how little i know
jo
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Dec 19, 2010 @ 1:13 pm
you didnt answer my question why cant things be easy for once
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Dec 30, 2010 @ 12:00 am
Happy the information is very helpful to me. I have many question in mind that i should later it conclude.
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Aug 28, 2011 @ 1:01 am
i have a friend his uncle has been pass away since eight years but still the dead body remains intact with no sign of decomposition.can you please explain this to me .
thank you in advance
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Aug 31, 2011 @ 9:09 am
Thanks for the GREAT information. My presentation is going to be great because of this THANKS!!
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Sep 6, 2011 @ 5:05 am
thank you very much for the very useful information! It will contribute a lot in my report in biology :)
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Oct 12, 2011 @ 3:15 pm
thanks for the information..
its great and its well understood..
God bless you all.. ^^
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Oct 13, 2011 @ 8:08 am
this was wonderful, thanks for all the great information. :)
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Nov 26, 2011 @ 3:15 pm
This was VERY helpful and awesome information!!! Thnx!
Hero007
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Feb 7, 2012 @ 12:00 am
Nice info, thanks!
Although I do agree with Caitlyn, You really need a better background.
MENZI
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Mar 26, 2012 @ 1:01 am
what negative effects of enhancing greenhouse effect?
Hannah
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Dec 19, 2012 @ 10:10 am
This was very helpful infomation! thank you so much ! ! ! ! ! !
Shosho Millionaire
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Jan 4, 2013 @ 5:05 am
okay nice but i still didn't get what i want !!? >_<
edris
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Feb 24, 2013 @ 1:01 am
what is the process of carbon dioxide to water bodies
dacota schaad
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Apr 26, 2013 @ 11:11 am
well this diagram was really nice and helped me ge a %100 A+ on my exam. thank you so much. :)
abdulhamid
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Jun 2, 2013 @ 10:10 am
What other names can you call the Calvin cycle?
Also, what else can you call the TCA cycle?
Haley
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Nov 5, 2013 @ 6:18 pm
Omg thanks have such big test tomorrow so I should go now bye✏📃📓 ugh hate school
student
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Jan 4, 2014 @ 3:03 am
Thank you for the information. It helps much for my assignment.
N.Iitiwaoybity
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May 30, 2014 @ 9:21 pm
"Decomposition is the largest source through which carbon is returned to the atmosphere as carbon dioxide."
Thank you. Most helpful.
cody
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Oct 23, 2014 @ 7:19 pm
I just want to thank you for the info. You should earn a degree in biochemistry with the potential you have!
lol loll
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Dec 16, 2014 @ 8:20 pm
Thanks for the info! Had to do a booklet on every cycle at school. P.s it is hard to do this.

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