Edexcel IGCSEBiologyGeneral Applications6 Marks
Microorganisms play essential roles in the carbon cycle.
- (a)Name the process by which microorganisms return carbon dioxide to the atmosphere.[1]
- (b)Describe the role of decomposers in the carbon cycle.[3]
- (c)Explain how deforestation can contribute to an increase in atmospheric carbon dioxide.[2]
Mark scheme
Marking points from the official mark scheme. The mark or mark type is shown in brackets.
- 17(a) B1: respiration / decomposition (1)
- 17(b) M1: decomposers (bacteria/fungi) break down dead organic matter / waste products (1)
- M1: release carbon compounds / CO2 (1)
- A1: by respiration / extracellular digestion (1)
- 17(c) M1: fewer trees means less photosynthesis (1)
- A1: so less carbon dioxide is removed from atmosphere (1)
- M1: burning trees releases carbon dioxide (1)
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