Component 1.5 - Carbon Cycle

Question 1

How is carbon returned to the atmosphere in the carbon cycle?

Answer 1

1) Burning of fossil fuels and trees
2) Respiration of producers, consumers and decomposers
3) Decay of organisms

Question 2

How is carbon dioxide removed from the atmosphere?

Answer 2

Photosynthesis of producers

Question 3

How is carbon passed on in the rest of the carbon cycle?

Answer 3

Carbon in producers is assimilated into consumers and when they both die there is carbon remaining in their tissues

Question 4

Under what conditions do dead organisms become fossil fuels?

Answer 4

When decay is prevented by anaerobic or acidic conditions the organisms may become fossilised into coal, oil or natural gas

Question 5

How is the carbon cycle similar/different in aquatic habitats?

Answer 5

• In aquatic ecosystems carbon dioxide as HCO3- ions undergoes the same process
• In addition carbon in consumers is incorporated into magnesium and calcium carbonate in mollusc shells and exoskeletons which sink after the organisms death and become components of chalk and limestone
• If chalk or limestone are exposed to the atmosphere they are eroded and release CO2

Question 6

How does deforestation impact the carbon cycle?

Answer 6

• The rate at which photosynthesis removes CO2 from the atmosphere is reduced by cutting down forests
• When trees are cut down they may be burned or left where they are to decay which both release CO2 back into the atmosphere

Question 7

Describe the greenhouse effect

Answer 7

1) Short wavelength solar radiation can pass through the atmosphere to the earths surface
2) Much energy is absorbed by the earth, which warms up and releases longer wavelength IR
3) This IR is absorbed and trapped by the greenhouse gases in the atmosphere
4) These tases re-radiate energy in all directions including back to the earths surface which again warms up

Question 8

Describe sources of the greenhouse gas, methane

Answer 8

1) A methane burp happens when methane clathrates on the ocean floor warm as sea temperatures rise
2) Melting arctic permafrost will also increase atmospheric methane

Question 9

Describe some consequences of global warming (weather and extreme events) - 4

Answer 9

1) Melting of polar ice caps resulting in flooding in coastal areas
2) Increased frequency of extreme weather e.g droughts, hurricanes and cyclones
3) Increased frequency of forest fires
4) Decreased availability of water leads to formation and expansion of deserts

Question 10

What are the consequences of global warming on animals and plants? - 3

Answer 10

1) Evolutionary adaption is slow so as climate changes animals must move to find a more suitable environment - cannot move fast enough
2) Plants can only move as fast as they are dispersed (slow) so they may become extinct
3) Animals dependent on the plants may then become extinct and an ecosystem could collapse

Question 11

What are the consequences of climate change on food production?

Answer 11

1) May be increased crop yields as higher temperatures means more photosynthesis
2) Pest populations may increase
3) World food production may decrease due to drought

Question 12

How to tackle

1) Decomposition of organic matter producing CO2
2) Decomposition in wet souls producing methane
3) Raised sea levels causing farming areas to be inundated by salt water
4) Low rainfall and high temperatures

Answer 12

1) Crop rotation (reduces pest numbers and mineral depletion) and conservation tilage leaving crop residue on top of soil to reduce erosion and add organic matter to soil
2) Use rice varieties that grow in drier conditions
3) Salt-tolerant crops
4) Drought-tolerant crops e.g those used in Kenya

Question 13

What is carbon footprint?

Answer 13

The equivalent amount of carbon dioxide generated by an individual, a product or service in a year