4.3 carbon cycling Flashcards
carbon cycle
is a biogeochemical cycle whereby carbon is exchanged between the different spheres of the Earth.
4 main carbon sinks
- atmosphere (air)
- lithosphere (ground)
- hydrosphere (water/oceans)
- biosphere (living things)
draw carbon cycle (7 things, 9 processes)
co2
things:
- vehicles combustion
- fuels
- animals
- plants
- fossils
- oceans
- CaCO3
processes:
- pollution
- respiration
- feeding
- decomposition
- fossilisation
- extraction
- sedimentation
- photosynthesis
- combustion
carbon is exchanged in the following forms:
- atmospheric gases - mainly co2 but also methane
- oceanic carbonates - incl bicarbonates dissolved in the water and calcium carbonate in corals and shells
- as organic materials - incl the carbohydrates, lipids, proteins found in all living things
- non-living remains - such as detritus and fossil fuels
the carbon dioxide levels within autotroph is
low as they use it for photosynthesis.
CO2 conc atmosphere > organism
concentration gradient ensures that carbon dioxide will passively diffuse into the autotrophic organism as required. in aquatic producers, CO2 can usually diffuse directly into the autotroph whereas in terrestrial plants, diffusion occurs at the stomate.
how are carbon compounds produced?
through photosynthesis, autotrophs govern inorganic carbon dioxide into organic compounds via photosynthesis.
cell respiration
- involves the breakdown of organic molecules (e.g. sugars) and produces carbon dioxide as a by-product.
- the build up co2 in respiring tissues creates a concentration gradient, allowing it to be removed by passive diffusion.
compensation point
in autotrophs where the uptake of co2 by photosynthesis is balanced by the production of co2 by respiration. net carbon assimilation is 0.
aquatic conversion of carbon dioxide in water
co2 form atmosphere ->ocean -> limestone +shells
- co2 in the atmosphere dissolves into water.
- part remains as a dissolved gas while the remainder combines w water to form carbonic acid.
- carbonic acid then dissociates to form hydrogen carbonate ions.
- conversion also releases hydrogen ions, causing the pH of water to rise consequently
- autotrophs absorb both dissolved carbon dioxide and hydrogen carbonate ions and use then to produce organic compounds.
- when hydrogen carbonate ions come into contact w the rocks and sediments on the ocean floor, they square metal ions.
- this results in the formation of calcium carbonate and the subsequent development of limestone. living
- living animals may also combine the hco3- ions w calcium to form calcium carbonate.
- this calcium carbonate forms the hardened exoskeleton of coral, as well as the main component of mollusca shells.
- when the organism dies and settles to the sea floor, these hard components may become fossilised in the limestone.
methanogens
are archaean microorganisms that produce methane (CH4) as a metabolic by-product in anaerobic conditions.
how to methanogens produce methane
from the by-products of anaerobic digestion, principally acetic acid(CH3COOH) and carbon dioxide.
acetic acid -> methane + co2
co2+h2 -> methane + water
how is methane produced?
- accumulated underground. when organic matter is buried in anoxic conditions (greatly deficient in oxygen/oxygenless) (e.g. sea beds), deposits of methane (natural gas) may form underground.
- by domesticated cattle farts - they got methanogens in their stomachs
- methanogens
why are methane levels in the atmosphere not very large even though significant quantities are being produced?
they will be naturally oxidised to form carbon dioxide and water.
partial decomposition producing fossil fuels
- waterlogged regions may lack oxygenated air spaced within soil and therefore possess anaerobic conditions.
- anaerobic conditions prompt anaerobic respiration by organisms within these regions which produce organic acids, resulting in acidic conditions.
- saprotrophic bacteria and fungi cannot function effectively in anaerobic/acidic conditions, preventing decomposition.
how is coal formed
- organic matter that is not fully decomposed in waterlogged soils, carbon-rich molecules remain in the soil and form peat.
- when deposits of peat are compressed under sediments, the heat and pressure force out impurities and remove moisture
- the remaining material has a high carbon concentration and undergoes a chemical transformation to produce coal.