4.3 Carbon cycling

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4.3 Carbon cycling

4.3 Carbon cycling



Essential idea:


4.3.1  Continued availability of carbon in ecosystems depends on carbon cycling.


Nature of science:


4.3.2  Making accurate, quantitative measurements—it is important to obtain reliable data on the concentration of carbon dioxide and methane in the atmosphere. (3.1)




4.3.3  Autotrophs convert carbon dioxide into carbohydrates and other carbon



4.3.4   In aquatic ecosystems carbon is present as dissolved carbon dioxide and

hydrogen carbonate ions.


4.3.5   Carbon dioxide diffuses from the atmosphere or water into autotrophs.


4.3.6   Carbon dioxide is produced by respiration and diffuses out of organisms into water or the atmosphere.


4.3.7   Methane is produced from organic matter in anaerobic conditions by

methanogenic archaeans and some diffuses into the atmosphere or

accumulates in the ground.


4.3.8   Methane is oxidized to carbon dioxide and water in the atmosphere.


4.3.9   Peat forms when organic matter is not fully decomposed because of acidic

and/or anaerobic conditions in waterlogged soils.


4.3.10  Partially decomposed organic matter from past geological eras was

converted either into coal or into oil and gas that accumulate in porous rocks.


4.3.11  Carbon dioxide is produced by the combustion of biomass and fossilized

organic matter.


4.3.12  Animals such as reef-building corals and mollusca have hard parts that are composed of calcium carbonate and can become fossilized in limestone.





4.3.13  Application: Estimation of carbon fluxes due to processes in the carbon cycle.

4.3.14  Application: Analysis of data from air monitoring stations to explain annual fluctuations.




4.3.15  Skill: Construct a diagram of the carbon cycle.




4.3.16  Carbon fluxes should be measured in gigatonnes.





4.3.17 Syllabus and cross-curricular links:



Topic 8.1 Energy sources




Topic C.2 Fossil fuels

Topic C.5 Environmental impact—global warming




4.3.18  Aim 8: The ethical implications of diverting crops such as maize from a food to a fuel crop could be considered.

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