carbon cycle

what do cycles have evolved to ensure that the chemical components of life are continually cycled through ecosystems contain?

• a biotic phase, during which the inorganic ions are incorporated in the tissues of living things

• an abiotic phase, during which the inorganic ions are returned to the non-living part of the ecosystem

what is carbon cycle?

a series of reactions by which carbon is constantly recycled between living things and the environment

where is carbon found?

• Carbon is found in the biomass of living organisms e.g. in carbohydrates and proteins

• Carbon is transferred when one organism consumes and digests another

• Carbon is found in the atmosphere as carbon dioxide and in the oceans as e.g. hydrogen carbonate ions

events that occur during carbon cycle

• Carbon is present in the atmosphere in the form of carbon dioxide

• Carbon dioxide is removed from the atmosphere by producers during photosynthesis

  • Producers incorporate carbon into their biomass in the form of carbohydrates and other biological molecules

• Carbon is transferred to and between consumers as a result of feeding

• Carbon is transferred back into the atmosphere by both plants and animals as a result of respiration

• Carbon dioxide can also be removed from the atmosphere by dissolving in the oceans

• Dissolved carbon can be taken in by marine plants when they photosynthesise or by other marine organisms as they build calcium carbonate exoskeletons

• When living organisms die their tissues are broken down by decomposers such as bacteria and fungi

  • When these organisms respire, they too release carbon dioxide back into the atmosphere

• Any living tissue that is not fully decomposed can go towards the formation of peat or fossil fuels over millions of years; carbon can be stored in these sinks for long periods

• The combustion of peat and fossil fuels releases carbon dioxide back into the atmosphere

  • The combustion of biomass such as wood also returns carbon to the atmosphere

what are carbon sinks

a reservoir where carbon dioxide is removed from the atmosphere and locked into organic or inorganic compounds

biotic part of carbon cycle

Carbon is removed from the atmosphere by photosynthesis

and stored in the bodies of plants in the biotic part of the

carbon cycle. Soil contains large quantities of organic carbon

rich material in the form of humus.

abiotic form of carbon cycle/stores

Rocks, limestone and chalk and fossil fuels like coal, oil and

gas are massive stores of carbon. These are carbon stores in

the abiotic parts of the system.

ocean carbon sinks

Atlantic ocean is a carbon sink, absorbs up to 23% of carbon

produced by humans each year. Although Southern ocean is

larger in area it contains less carbon.

Due to different temperatures and ocean currents.

how is quantity of carbon stored measured

• Quantity of carbon stored in sinks is measured in petagrams.

1 petagram is 1015 grams and this is 1 billion tonnes.

• Photosynthesis removes 110 petagrams of carbon each year

from the atmosphere and this is transferred to the bodies of

living organisms.

how carbon cycle regulates itself?

• there is a balance between the amounts of carbon released in respiration and other natural processes and those absorbed in photosyntheis so that atmospheric carbon dioxide levels remain relatively steady

how humans have threatened balance of carbon cycle

• there has been an enormous increase in production of carbon dioxide by people since Industrial Revolution in the 18th and 19th centuries

• the industrially related output of carbon dioxide, combined with the development of the internal combustion engine for vehicles threatens balance of carbon cycle

why a good understanding of carbon cycle is important?

• It is possible to see the points at which carbon enters the atmosphere; reducing the carbon transfer at these points will prevent further increases in atmospheric carbon dioxide e.g.

  • Reducing the combustion of fossil fuels

  • Reducing the combustion of biomass

  • Reducing disturbance of carbon pools such as soils and peat bogs

• We can also see the points at which carbon is removed from the atmosphere; increasing the transfers here could help to reduce the greenhouse effect e.g.

  • Increasing rates of photosynthesis by planting trees