DP Biology (first assessment 2025)

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Question 23M.2.SL.TZ2.17b

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Date May 2023 Marks available [Maximum mark: 2] Reference code 23M.2.SL.TZ2.17b
Level SL Paper 2 Time zone TZ2
Command term Describe Question number b Adapted from N/A
b.
[Maximum mark: 2]
23M.2.SL.TZ2.17b

The diagram represents primary succession that occurs in an Arctic ecosystem, on a river floodplain in Alaska, USA. Permafrost is permanently frozen subsoil found in Arctic regions.

[Source: Bonanza Creek LTER.]

(b)

Describe two limiting factors on this ecosystem.

[2]

Markscheme
  1. light limits photosynthesis
    OR
    daylength limits growth season;
  2. (low) temperature limits growth/slows metabolism
    OR
    (low) temperature slows activity of decomposers;
  3. (lack of) water due to frozen water/permafrost
    OR
    (lack of) water/rain limits photosynthesis/productivity;
  4. nutrients (in permafrost)/quality/depth of soil limit production of organic molecules / OWTTE
    OR
    insufficient soil / permafrost for tree growth;

Award marks only for factors accompanied by a description.

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