4.3 carbon cycling Flashcards

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1
Q

carbon cycle

A

is a biogeochemical cycle whereby carbon is exchanged between the different spheres of the Earth.

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2
Q

4 main carbon sinks

A
  1. atmosphere (air)
  2. lithosphere (ground)
  3. hydrosphere (water/oceans)
  4. biosphere (living things)
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3
Q

draw carbon cycle (7 things, 9 processes)

A

co2

things:
- vehicles combustion
- fuels
- animals
- plants
- fossils
- oceans
- CaCO3

processes:
- pollution
- respiration
- feeding
- decomposition
- fossilisation
- extraction
- sedimentation
- photosynthesis
- combustion

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4
Q

carbon is exchanged in the following forms:

A
  1. atmospheric gases - mainly co2 but also methane
  2. oceanic carbonates - incl bicarbonates dissolved in the water and calcium carbonate in corals and shells
  3. as organic materials - incl the carbohydrates, lipids, proteins found in all living things
  4. non-living remains - such as detritus and fossil fuels
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5
Q

the carbon dioxide levels within autotroph is

A

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.

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6
Q

how are carbon compounds produced?

A

through photosynthesis, autotrophs govern inorganic carbon dioxide into organic compounds via photosynthesis.

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7
Q

cell respiration

A
  • 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.
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8
Q

compensation point

A

in autotrophs where the uptake of co2 by photosynthesis is balanced by the production of co2 by respiration. net carbon assimilation is 0.

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9
Q

aquatic conversion of carbon dioxide in water

A

co2 form atmosphere ->ocean -> limestone +shells

  1. co2 in the atmosphere dissolves into water.
  2. part remains as a dissolved gas while the remainder combines w water to form carbonic acid.
  3. carbonic acid then dissociates to form hydrogen carbonate ions.
  4. conversion also releases hydrogen ions, causing the pH of water to rise consequently
  5. autotrophs absorb both dissolved carbon dioxide and hydrogen carbonate ions and use then to produce organic compounds.
  6. when hydrogen carbonate ions come into contact w the rocks and sediments on the ocean floor, they square metal ions.
  7. this results in the formation of calcium carbonate and the subsequent development of limestone. living
  8. living animals may also combine the hco3- ions w calcium to form calcium carbonate.
  9. this calcium carbonate forms the hardened exoskeleton of coral, as well as the main component of mollusca shells.
  10. when the organism dies and settles to the sea floor, these hard components may become fossilised in the limestone.
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10
Q

methanogens

A

are archaean microorganisms that produce methane (CH4) as a metabolic by-product in anaerobic conditions.

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11
Q

how to methanogens produce methane

A

from the by-products of anaerobic digestion, principally acetic acid(CH3COOH) and carbon dioxide.

acetic acid -> methane + co2
co2+h2 -> methane + water

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12
Q

how is methane produced?

A
  1. 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.
  2. by domesticated cattle farts - they got methanogens in their stomachs
  3. methanogens
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13
Q

why are methane levels in the atmosphere not very large even though significant quantities are being produced?

A

they will be naturally oxidised to form carbon dioxide and water.

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14
Q

partial decomposition producing fossil fuels

A
  1. waterlogged regions may lack oxygenated air spaced within soil and therefore possess anaerobic conditions.
  2. anaerobic conditions prompt anaerobic respiration by organisms within these regions which produce organic acids, resulting in acidic conditions.
  3. saprotrophic bacteria and fungi cannot function effectively in anaerobic/acidic conditions, preventing decomposition.
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15
Q

how is coal formed

A
  1. organic matter that is not fully decomposed in waterlogged soils, carbon-rich molecules remain in the soil and form peat.
  2. when deposits of peat are compressed under sediments, the heat and pressure force out impurities and remove moisture
  3. the remaining material has a high carbon concentration and undergoes a chemical transformation to produce coal.
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16
Q

how is oil/natural gas formed

A
  1. Oil (i.e. petroleum) and natural gas form as the result of the decay of marine organisms on the ocean floor
  2. Sediments (e.g. clay and mud) are deposited on top of the organic matter, creating anoxic conditions that prevent decomposition
  3. As a result of the burial and compaction, the organic material becomes heated and hydrocarbons are formed
  4. The hydrocarbons form oil and gas, which are forced out of the source rock and accumulate in porous rocks (e.g. sandstone)
  5. The formation of fossil fuels (coal, oil and gas) takes place over millions of years, making them a non-renewable energy source
17
Q

sources of combustion

A
  1. fossil fuels
  2. biomass
18
Q

carbon fluxes

A

describe the rate of exchange of carbon between the various carbon sinks / reservoirs

19
Q

The rate at which carbon is exchanged between these reservoirs depends on the conversion processes involved:

A
  1. Photosynthesis – removes carbon dioxide from the atmosphere and fixes it in producers as organic compounds
  2. Respiration – releases carbon dioxide into the atmosphere when organic compounds are digested in living organisms
  3. Decomposition – releases carbon products into the air or sediment when organic matter is recycled after death of an organism
  4. Gaseous dissolution – the exchange of carbon gases between the ocean and atmosphere
  5. Lithification – the compaction of carbon-containing sediments into fossils and rocks within the Earth’s crust (e.g. limestone)
  6. Combustion – releases carbon gases when organic hydrocarbons (coal, oil and gas) are burned as a fuel source
20
Q

factors that affect the exchange of carbon between different sinks

A
  1. climate conditions: rate of photosynthesis is likely to be higher in summer seasons as more direct sunlight and longer days. oceanic temperatures also determine how much carbon is stored as dissolved CO2 or as dissolved hydrogen bicarbonate ions. climate events like el nino(warming) and la nina(cooling) will change the rate of carbon flux between ocean and atmosphere. melting of polar ice caps will result in the decomposition of frozen detritus.
  2. natural events: forest fires can release high levels of carbon dioxide when plants burn (loss of trees also reduces photosynthetic carbon uptake). volcano eruptions can release carbon compounds from the Earth’s crust into the atmosphere.
  3. human activities: cleaning of trees for agriculture purposes (deforestation) will reduce the removal of atmospheric CO2 via photosynthesis. increased numbers of ruminant livestock while produce higher levels of methane. the burnin of fossil fuels release co2
21
Q

atmospheric CO2 as measured by charles keeling reason of fluctuation pattern

A
  1. CO2 levels fluctuate annually (lower in the summer months when long days and more light increase photosynthetic rates)
  2. Global CO2 trends will conform to northern hemisphere patterns as it contains more of the planet’s land mass (i.e. more trees)
  3. CO2 levels are steadily increasing year on year since the industrial revolution (due to increased burning of fossil fuels)
  4. Atmospheric CO2 levels are currently at the highest levels recorded since measurements began