plumiDecomposition and the carbon cycle: Edexcel International A Level Biology questions
Edexcel International A Level Biology past-paper questions on 6.5.1 Decomposition and the carbon cycle, 2019–2025, with mark schemes and examiner’s reports where available.
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Q5(b)(i)
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All 21 questions on Decomposition and the carbon cycle, as a list
- January 2025, Unit 4, Q5(b)(i) (1 mark): Which is the difference between the maximum and minimum temperatures in May? (1) A 5°C B 8°C C 10°C D 16°C
- January 2025, Unit 4, Q5(b)(ii) (5 marks): Explain how the conditions in the peat bog preserved the body of this man. Use the information in the question and your own knowledge to support your answer. (5
- June 2024, Unit 4, Q4(b)(i) (1 mark): Decomposition was measured as a decrease in dry mass of the leaves. Suggest why dry mass was measured and not wet mass. (1)
- June 2024, Unit 4, Q4(b)(ii) (2 marks): Calculate the rate of decrease in percentage dry mass between 30 days and 120 days for the sugar maple leaves. Give your answer to two significant figures. (2)
- June 2024, Unit 4, Q4(b)(iii) (2 marks): Describe two conclusions that can be made about the decomposition of sugar maple leaves compared with the white oak leaves. (2)
- June 2024, Unit 4, Q4(c)(i) (1 mark): Calculate how many times greater the biomass of bacteria on the sugar maple leaves is after 30 days compared with the biomass of bacteria at 0 days. (1) Answer
- June 2024, Unit 4, Q4(c)(ii) (2 marks): Suggest why the increase in biomass of bacteria after 30 days is greater on the sugar maple leaves than it is on the white oak leaves. Give a reason for your an
- June 2024, Unit 4, Q4(c)(iii) (2 marks): Suggest why the biomass of bacteria on the white oak leaves decreased after 90 days. Give a reason for your answer. (2)
- October 2023, Unit 4, Q8(a)(iii) (3 marks): Explain the importance of enzymes produced by microorganisms in decomposition. (3)
- January 2023, Unit 4, Q3(b)(ii) (2 marks): Scientists are developing methods that use microorganisms to break down plastics. Some of the products produced are being used for other purposes, such as vanil
- January 2023, Unit 4, Q3(b)(iii) (3 marks): One type of bacteria, Pseudomonas, uses half of the plastic it breaks down to produce its own biomass, with the rest released as carbon dioxide. Explain how the
- June 2022, Unit 4, Q5(a)(v) (3 marks): Describe the role of microorganisms in recycling carbon present in this food chain. (3)
- January 2022, Unit 4, Q8(b)(iii) (4 marks): Explain the changes in mass of this mammal during decomposition. (4)
- October 2021, Unit 4, Q7(a)(i) (1 mark): The teabags had to be dried before weighing to remove water. One teabag contained 28 g of tea when it was buried. When it was dug up it had a wet mass of 42 g.
- October 2021, Unit 4, Q7(a)(ii) (2 marks): Calculate the rate at which the relative mass of the green tea decreases in the teabags buried at 15 °C at day 30. (2) Answer
- October 2021, Unit 4, Q7(a)(iii) (4 marks): Explain the difference in the decrease in relative mass of green tea in teabags buried at 15 °C and 25 °C. Use the information in the graph to support your answ
- October 2021, Unit 4, Q7(a)(iv) (2 marks): Suggest why the rate of decomposition of green tea was different from that of rooibos tea. (2)
- October 2021, Unit 4, Q7(b)(ii) (3 marks): Explain which ecosystems should be conserved to have the greatest impact on climate change. Use the information in the graph to support your answer. (3)
- June 2021, Unit 4, Q6(b)(iii) (3 marks): Describe how the carbon present in sugars in the plants is returned to the atmosphere in the carbon cycle. (3)
- January 2021, Unit 4, Q8(b)(iii) (6 marks): Explain the role of decomposition in returning the carbon present in the carbohydrates in the quince fruit back into the atmosphere. Use the information given i
- January 2020, Unit 4, Q2(a)(i) (2 marks): Explain why scientists think that plastics could be broken down by microorganisms. (2)
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