Biological control is one method used to help feed the growing human population. Explain how biological control works and outline one advantage and one disadvantage of using biological control instead of pesticides.

OCR GCSE Biology A: Gateway Science (J247) — B6.2 Feeding the human race · Explain · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Farmers are under pressure to increase crop yields to feed the growing human population. One approach that avoids the use of chemical pesticides is biological control, which involves introducing a natural predator or pathogen to reduce pest numbers.

Model answer (4 marks)

Biological control works by introducing a natural predator, parasite or pathogen that attacks the pest population. The predator feeds on the pest or the pathogen infects and kills it, which reduces the number of pests that damage crops and therefore increases crop yield.

Advantage: it avoids the use of chemical pesticides, so there is no chemical pollution of the environment, water supply or soil.

Disadvantage: the introduced organism can become a pest itself, may harm non‑target species or reduce biodiversity.

Examiner tips

  • Use the word ‘introducing’ and ‘predator/parasite/pathogen’ to show understanding of the method.
  • Mention the effect on crop yield explicitly.
  • Give one clear advantage and one clear disadvantage, using the terms ‘chemical pollution’ and ‘non‑target species’ or ‘biodiversity’.

Common mistakes

  • Mixing up the roles of predator and pest, e.g. saying the pest eats the crop instead of the predator eating the pest.
  • Failing to mention the impact on crop yield or the environmental benefit of avoiding chemicals.
  • Giving a disadvantage that is not specific to biological control, such as general pesticide side effects.

Mark scheme (4 marks)

  1. Biological control involves introducing a natural predator (or pathogen/parasite) to reduce the number of pests
  2. The predator eats (or the pathogen infects) the pest, reducing damage to crops and increasing yield
  3. One advantage: biological control does not involve chemicals / pesticides, so there is no chemical pollution of the environment / water supply / soil
  4. One disadvantage: the introduced organism may itself become a pest / harm non-target species / reduce biodiversity

Key terms in this question

biological control · pest · pesticides

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