Explain how the use of pesticides in farming can have harmful effects on organisms that are not the target pest.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Farmers use chemical pesticides to kill insects and other organisms that damage their crops. However, conservation groups have raised concerns about the wider effects of pesticides on ecosystems.
Model answer (5 marks)
Pesticides can persist in the environment after application, remaining in soil, water and on plant surfaces.
Non‑target organisms such as bees, birds and other insects can then consume or absorb the pesticide.
The chemical may accumulate in the tissues of these organisms – a process called bioaccumulation.
At higher trophic levels the concentration of pesticide increases, a phenomenon known as biomagnification.
When the concentration becomes too high, it can harm or kill non‑target organisms, which in turn disrupts food chains and ecological balance.
Non‑target organisms such as bees, birds and other insects can then consume or absorb the pesticide.
The chemical may accumulate in the tissues of these organisms – a process called bioaccumulation.
At higher trophic levels the concentration of pesticide increases, a phenomenon known as biomagnification.
When the concentration becomes too high, it can harm or kill non‑target organisms, which in turn disrupts food chains and ecological balance.
Examiner tips
- Use the exact terms ‘bioaccumulation’ and ‘biomagnification’
- Show the sequence from persistence to harm
- Include at least one non‑target group (bees, birds, insects)
Common mistakes
- Confusing bioaccumulation with biomagnification
- Omitting the step that pesticides remain in the environment
- Failing to mention the disruption of food webs
Mark scheme (5 marks)
- Pesticides can remain in/on the environment (soil, water, plants) after application
- Non-target organisms (e.g. bees / birds / other insects) consume/absorb the pesticide
- Pesticides accumulate/build up in the tissues of organisms (bioaccumulation)
- Concentration of pesticide increases at higher trophic levels / in predators (biomagnification)
- High concentrations of pesticide harm or kill non-target organisms, disrupting food chains/webs
Key terms in this question
Related
- All Eduqas A-Level Biology revision notes →
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- Decode the mark scheme abbreviations →
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