A farmer uses pesticides on crops over many years. A hawk that hunts small mammals in those fields is found to have pesticide concentrations thousands of times higher than the soil. Explain, step by step, the process responsible for this, and predict whether a human who regularly eats those hawks would have even higher concentrations.
Generated by claude-sonnet-4-6 · 2026-06-26 00:58 · grounding rag
Model Answer
Biological Magnification:
Pesticides sprayed on crops are absorbed by plants (1st trophic level). Small mammals eat large amounts of these plants, so pesticides accumulate in their bodies (2nd trophic level). The hawk eats many such mammals, concentrating the chemical further (3rd trophic level). Since pesticides are non-biodegradable, they are not broken down and keep accumulating — a process called biological magnification.
A human regularly eating those hawks (4th/higher trophic level) would have even higher pesticide concentrations, because humans occupy the top trophic level where maximum accumulation occurs.
Source: Chapter 13, Section 13.1.1 (Biological Magnification)
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Explanation
- Examiners expect the term biological magnification to be used and defined/implied.
- Key idea: non-biodegradable chemicals increase in concentration at each successive trophic level.
- The three steps to mention: absorption by plants → accumulation in herbivores/small animals → further concentration in carnivores.
- For the prediction part, simply state yes, higher concentration, because humans are at the top trophic level — this fetches the final mark.
- Don't write a long essay; the 3-mark limit means roughly 3 clear points.