Topic 4.3: Carbon cycling Flashcards
Definition of Carbon Cycle
Biogeochemical cycle whereby carbon is exchanged between the different spheres of the Earth
Spheres of the Earth and forms of carbon (4)
a) Hydrosphere (Water) = = HCO3- (aq) / CaCO3 in corals
b) Biosphere (Living things) = Carbohydrates / lipids / proteins
c) Lithosphere (Ground) = Detritus / Fossil fuels
d) Atmosphere (Air) = CO2 / CH4
Diagram of the carbon cycle
a) Sinks
b) Fluxes
Check notes
a) Carbon compounds in fossil fuels
b) Carbon compounds in producers
c) Carbon compounds in dead organic matter
d) Carbon compounds in consumers
e) CO2 in the atmosphere and hydorsphere
CO2 conversions in biosphere
a) Photosynthesis
b) Cell respiration
Autotrophs in CO2 conversion via cell respiration
a) Produce ATP to power metabolic processes
b) CO2 is produced as a byproduct, so it builds up in respiring tissues.
c) Concentration gradient ensures that CO2 can diffuse out.
Organisms in CO2 conversion via photosynthesis
a) Converts CO2 into organic compounds via photosynthesis
b) The CO2 level within an autotorph shoudl lower than the one of the surroundings.
c) This concentration gradient ensures that CO2 can diffuse from the water / air into the autotroph.
CO2 conversions in aquatic environments
a) Dissolution of CO2 in water
b) Calcification and formation of limestone
Dissolution of CO2 in water
a) CO2 dissolves in water to form carbonic acid
b) This increases acidity of water
c) Acidic water can dissolve organism shells and make them more prone to predation
Calcification and formation of limestone
a) Living animals can combine HCO3– with Ca to form CaCO3
b) CaCO3 forms the hardened exoskeleton of coral, as well as the main component of mollusca shells
c) When the organism dies and settles to the sea floor, these components may become fossilized in limestone
CH4 production
a) Organism
b) Condition
a) Bacteria / Methanogenic archaean
b) Anaerobic conditions
Process of CH4 production
a) Bacteria convert organic matter into a mixture of organic acids, alcohol, H2 and CO2
b) Bacteria use the organic acids and alcohol to produce acetate, CO2 and H2
c) CH4 is produced from the by-products of anaerobic digestion
CH4 oxidation
a) Accumulation under the ground
b) Diffusion into the atmosphere
c) CH4 naturally oxidizes to form H2O and CO2
Definition of Peat
Waterlogged soil that contains large amounts of partially decomposed organic matter
Formation of peat (4)
a) Waterlogged regions lack oxygenated air spaces wihtin the soil (Anaerobic condtions)
b) Saprotrophic organisms use anaerobic respiration to produce organic acids, resulting in acidic conditions.
c) These organisms cannot function in acidic / anaerobic conditions, preventing decomposition.
d) Large quantities of partially decomposed organic matter have accumulated and become compressed.
Formation of coal
a) Deposits of peat (from past geological eras) are compressed under sediments (⇑pressure / ⇑heat)
b) This compression of peat removes impurities and produces coal.
Formation of oil / natural gas
a) Sediments are deposited on top of organic matter, preventing decomposition due to anoxic conditions.
b) Compaction causes organic material to become heated, and hydrocarbons are produced.
c) Hydrocarbons form oil and gas, which are forced out the source rock and accumulate in porous rocks.
Description of combustion
a) Exothermic reaction that produces H2O + CO2
b) Organic compounds rich in hydrocarbons undergo combustion in the presence of heat and O2
Sources of hydrocarbons
a) Fossilized organic matter (e.g., coal, oil and gas)
b) Biomass (e.g., bioethanol and biofuels)
Purpose of carbon fluxes
Describe the rate of exchange of carbon between the various carbon sinks
Conversion processes of carbon (gigatons per year)
a) Photosynthesis
b) Respiration
c) Gaseous dissolution
d) Decomposition
e) Lithification
f) Combustion
Description of Photosynthesis
Fixation of CO2 from the atmosphere to autotrophs as organic compounds
Description of Respiration
Release of CO2 into the atmosphere when organic compounds are digested.
Description of Gaseous Dissolution
Exchange of carbon gases between the ocean and atmosphere
Description of Decomposition
Release of carbon products into sediment when organic matter is recycled after death of an organism
Description of Lithification
Compaction of carbon-containing sediments into fossils and rocks
Causes for flux change
a) Forest fires
b) Volcanic eruptions
c) Deforestation
d) Increase numbers of livestock
e) Burning of fossil fuels
Fluctuations in atmospheric CO2 concentrations
a) CO2 levels fluctuate annually. Lower in the summer months when long days and more light increase photosynthetic rate
b) CO2 trends conform to norhtern hemisphere patterns as it contains more of the planet’s land mass
