Topic 4.3

Question 1

Carbon dioxide and water equation
(Carbon dioxide combined with water)

Note: some will dissolve, but most will combine

Answer 1

CO2 + H2O —> H2CO3 (carbonic acid) —> H(+) + HCO3(-)

H+ ions lowers pH of water

Dissolved CO2 and H2CO3 are absorbed by aquatic plants and other autotrophs in water

Question 2

Autotrophs role in CO2 cycle

Answer 2

Absorb CO2 from environment and convert it into organic compounds
- reduces concentration of CO2 in atmosphere by approx. 0.039% or 390 micromoles/mole

Question 3

What keeps the concentration of CO2 inside the leaf of an autotroph low?

Answer 3

Photosynthesis

Question 4

CO2 in autotrophs

Answer 4

1. Photosynthesis maintains concentration gradient of CO2
2. CO2 from outside the leaf diffuses into the leaf
3. CO2 moves through stomatal pores in leaves of land plants - in many aquatic plants diffusion occurs directly through surface tissues

Question 5

CO2 in aerobic respiration

Answer 5

CO2 is a waste product of aerobic respiration

• co2 diffuses out of cells into the atmosphere or surrounding water

Includes
Autotroph (plants)
Heterotrophs (animals)
Saprotrophs and decomposers (fungi and bacteria)

Question 6

What are Methanogens?

Answer 6

Archean microorganisms that produce methane as a metabolic byproduct in anaerobic respiration

methane produced from carbon dioxide

Question 7

Where are methanogens found

Answer 7

• Wetlands (paddies, swamps, mangroves)
• digestive tracts of animals (cows, humans, termites)
• Marine and freshwater sediments (mud in lakebeds)
• landfill sites (in which organic matter has been buried)

Question 8

How long does methane persist in the atmosphere?

Answer 8

12 years, naturally oxidized in the stratosphere

Question 9

Methane oxidization by hydroxyl radicals

Answer 9

Methane + hydroxyl radical —> carbon dioxide + water

Question 10

What is peat?

(+ conditions)

Answer 10

Partially decomposed brown soil-like organic matter that is compressed

Not fully decomposed because of acidic and/or anaerobic conditions in waterlogged soils

• carbon sink
• can be used as fuel

Question 11

How is coal formed?

Answer 11

1. Deposits of peat are buried under other sediments
2. Peat is compressed and heated over millions of years, eventually becoming coal

• the cycle of sea-level changes that happened during the Carboniferous period caused coastal swamps to be buried promoting the formation of coal

Question 12

How is oil and natural gas formed?

Answer 12

1. Oil and natural gas are formed in the mud and at the bottom of seas and lakes
2. Anaerobic conditions mean decomposition is incomplete
3. Mud and sediment are deposited and partially decomposed organic matter is compressed and heated
4. Chemical changes produce mixtures of liquid carbon compounds or gases
5. Deposits are mostly found in porous rocks

Question 13

Carbon dioxide produced by the combustions of biomass and fossilized organic matter
(+ equation)

Answer 13

Combustion: heated dried biomass or fossilized fuels will burn in the presence of oxygen.
Fossil fuels/biomass + O2 —> CO2 + H2O

• Natural forest/grass fires occur in some regions
• human-caused fires for clearing areas (agriculture or harvesting)

Question 14

Animals that are composed of calcium carbonate

Answer 14

• Mollusc shells
• exoskeleton of hard corals

Question 15

How do animals contribute to deposits on the ocean floor?

Answer 15

When mollusc shells and exoskeletons of hard corals die, their soft body parts decompose but the CaCO3 remain (CaCO2 dissolves in acidic conditions)

• deposits are buried and eventually form limestone rock
• imprints of hard body parts remain in rock as fossils
• limestone is a huge carbon sink

Question 16

Pool

Answer 16

Reserve of C

Question 17

Flux

Answer 17

Transfer of C from one pool to another