Home / IB DP Biology- D4.2 Stability and change – IB Style Questions For SL Paper 2

IB DP Biology- D4.2 Stability and change - IB Style Questions For SL Paper 2 - FA 2025

IBDP Biology Paper 2 - All Chapters

Question

Gersmehl diagrams for two ecosystems are shown.

a. Identify the processes represented by the arrows labelled A and B in both diagrams. [2]

b. Deduce, with a reason, which ecosystem is representative of a tropical rainforest. [2]

▶️ Answer/Explanation

a.

  • A: Decomposition– the process by which litter is broken down and nutrients are transferred to the soil.
  • B: Leaching– the process by which nutrients are lost from the soil, often due to water movement.

b.

  • Ecosystem I is the tropical rainforest.
  • This is because it shows:
    • Low litter levels due to rapid decomposition (thicker arrow from litter to soil).
    • High biomass, consistent with high productivity typical of rainforests.
    • High leaching from soil (thick arrow B), which is due to heavy rainfall in tropical regions.

Markscheme

a.
a. Process A: decomposition/decay
b. Process B: leaching/erosion/run-off/weathering

b.
a. Ecosystem I
b. Low levels of litter due to high rates of decomposition
OR
High amounts of biomass related to high rates of productivity
OR
Weathering/leaching due to high rates of precipitation

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