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DP IB Biology: HL

Topic Questions

Home / IB / Biology: HL / DP / Topic Questions / 4. Ecology / 4.2 Carbon Cycling & Climate Change / Structured Questions: Paper 2


4.2 Carbon Cycling & Climate Change

Question 1a

Marks: 2
a)

Tundra soils are mainly composed of peat that forms in the extreme cold conditions found within this ecosystem. Peat contains large amounts of carbon which is released when the tundra soils thaw during warmer seasons. Scientists investigated the amount of carbon released from tundra soils at one location, that were thawed to different extents over the course of three years. The results from this investigation can be seen in the graph below.

2QmV30Gw_h-1a

Explain why tundra soils act as a carbon store.

[2 marks]

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    Key Concepts
    Formation of Peat

    Question 1b

    Marks: 2
    b)

    Calculate the difference in the mean carbon loss that occurred in tundra soils that were thawed considerably and those that were thawed slightly. Show your working.

    [2 marks]

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      Question 1c

      Marks: 2
      c)

      Compare the rate of carbon release in moderately thawed soils with those in soils that were considerably thawed.

      [2 marks]

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        Question 1d

        Marks: 2
        d)

        Scientists concluded that the carbon released from the considerable thawing of tundra soils will lead to a further increase in global temperatures.

        Evaluate this statement based on the investigation that was done.

        [2 marks]

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          Question 2a

          Marks: 3
          a)

          The following data show fluxes in carbon between different storage reserves in an ecosystem, measured in gigatonnes per year (GT yr-1). A gigatonne equals 1 billion tonnes.

          Process of carbon transfer Flux / GT yr-1
          Release from the oceans 101
          Ocean dissolving 104
          Release from soil 62
          Incomplete decomposition 52
          Respiration of terrestrial organisms 53
          Photosynthesis 117
          Deforestation 2.0
          Combustion of fossil fuels 4.9

          i)

          Calculate the net flux of carbon. Show your working.

          [2 marks]

          ii)

          State the direction of this movement with regards to the atmosphere.

          [1 mark]

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            Question 2b

            Marks: 2
            b)

            Explain how the combustion of fossil fuels can affect the carbon balance in the atmosphere.

            [2 marks]

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              Question 2c

              Marks: 2
              c)

              Estimating global carbon fluxes are of great interest to scientists, even though it may be challenging to make accurate measurements.

              Discuss the scientific importance of estimating carbon fluxes.

              [2 marks]

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                Question 3a

                Marks: 2
                a)

                Methane is an example of a greenhouse gas that commonly occurs in the atmosphere. The graph below shows the main sources of methane as well as the percentage contribution of the different components of each source. A teragram (Tg) equals 1012 grams and is equivalent to one megatonne (1 million tonnes).

                ~3Atp1Rj_h-3a-1

                Calculate the amount of methane, in Tg year-1, that is released from wetlands. Show your working.

                [2 marks]

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                  Key Concepts
                  Methanogenesis

                  Question 3b

                  Marks: 2
                  b)

                  Suggest a reason why wetlands would be the largest contributor of atmospheric methane, as shown in the graph above.

                  [2 marks]

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                    Key Concepts
                    Methanogenesis

                    Question 3c

                    Marks: 2
                    c)

                    Recent studies predict a decrease in levels of hydroxyl radicals in the atmosphere of between 10% and 16%. Hydroxyl radicals are often called the 'detergent of the atmosphere' and plays an important part in regulating atmospheric levels of gases such as methane.

                    i)

                    Predict the possible long-term effect these decreased levels of hydroxyl radicals could have on atmospheric concentrations of methane.

                    [1 mark]

                    ii)

                    Explain your answer to part c) i).

                    [1 mark]

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                      Key Concepts
                      Oxidation of Methane

                      Question 4a

                      Marks: 3
                      a)

                      Carbon dioxide is one of the main greenhouse gases in the atmosphere. The graph below shows the changes of carbon dioxide levels in the atmosphere, as well as the change in global temperatures over a period of time.yGzx-90Q_h-4a

                      Describe the general trends in the data.

                      [3 marks]

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                        Question 4b

                        Marks: 2
                        b)

                        Suggest possible causes of the trends in the data presented in part (a).

                        [2 marks]

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                          Key Concepts
                          Greenhouse Effect

                          Question 4c

                          Marks: 2
                          c)

                          Discuss the importance of greenhouse gases, such as carbon dioxide, in the atmosphere.

                          [2 marks]

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                            Key Concepts
                            Greenhouse Effect

                            Question 5a

                            Marks: 5

                            One mark is available for clarity of communication throughout this question.

                            a)

                            Coal, oil and natural gas are all examples of fossil fuels that can be utilised as an energy source.

                            Compare and contrast the formation of coal with that of oil and natural gas.

                            [5 marks]

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                              Key Concepts
                              Fossilisation

                              Question 5b

                              Marks: 6
                              b)

                              The amount of carbon in the atmosphere is constantly changing over time. Carbon dioxide and methane gases contribute to carbon levels in the atmosphere and have important impacts on the planet.

                              Discuss the importance of obtaining reliable data on the atmospheric concentration of these gases over time.

                              [6 marks]

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                                Question 5c

                                Marks: 3
                                c)

                                Suggest the possible impact that an increase in global temperatures would have on the polar regions, as well as the global consequences of this impact.

                                [3 marks]

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