O-LevelBiologyEcology & Environment5090/11 · Oct/Nov 2025 · Q391 Mark

Trees in a forest need a constant supply of nitrates to continue growing. The diagram shows some of the stages of the nitrogen cycle that provide the necessary nitrates. [Figure 39.1] Which stage in this cycle is not brought about by living bacteria?

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Alightning

Buptake of nitrates by plants

Cdecomposition of animal excreta

Dnitrification

✓ Correct answer

B: uptake of nitrates by plants

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Topic: Ecology & Environment, O-Level Biology (syllabus 5090). Multiple choice, 1 mark.
Source: O-Level Biology, Oct/Nov 2025 Paper 1 Variant 1, question 39.

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