Long answer·Hard exam skill (4/5)·No calculator
Difficulty guide
The label describes the problem, not your ability.
1/5 - Foundational
Warm-up setup; checks one basic idea.
2/5 - Routine exam skill
Normal syllabus skill; usually one main rule or interpretation.
3/5 - Standard multi-step
Exam-style problem with multiple steps or a common trap.
4/5 - Hard exam skill
High-end exam problem; combines methods carefully.
5/5 - Challenge
Stretch problem beyond normal exam pressure.
Question
A town uses a persistent pesticide near a lake to control insects. After months, tests show pesticide traces in plankton, fish and fish-eating birds.
Total: 6 marks
(a) Explain how the pesticide can reach fish-eating birds. (2 marks)
(b) Why may birds show a greater effect than plankton? (2 marks)
(c) Suggest two changes in pest-control practice that reduce this risk. (2 marks)
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