Describe how biological control can be used to reduce pest numbers on a crop, and explain one advantage and one disadvantage of using biological control instead of pesticides.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Farmers can reduce pest damage to crops either by applying pesticides or by using biological control methods that introduce another species to kill the pest.
Model answer (4 marks)
Biological control uses a natural predator or parasite that is released into the crop to feed on or kill the pest, thereby reducing its numbers.
Advantage: it avoids the use of chemical pesticides, so there is no chemical pollution of soil, water or the wider environment and it is more sustainable.
Disadvantage: the introduced species can become a pest itself or may affect other species in the ecosystem, and it can be difficult to control once released.
Advantage: it avoids the use of chemical pesticides, so there is no chemical pollution of soil, water or the wider environment and it is more sustainable.
Disadvantage: the introduced species can become a pest itself or may affect other species in the ecosystem, and it can be difficult to control once released.
Examiner tips
- Use the word ‘predator’ or ‘parasite’ to show you know the mechanism.
- Mention that it reduces chemical pollution to gain the advantage mark.
- State a specific ecological risk for the disadvantage to show depth.
Common mistakes
- Confusing biological control with crop rotation or mechanical methods.
- Failing to mention the environmental benefit or the risk of the introduced species becoming a pest.
Mark scheme (4 marks)
- Biological control involves introducing/using another species (natural predator/parasite) to kill or reduce the numbers of the pest
- The introduced species feeds on / kills / reduces the population of the pest
- One advantage: biological control does not involve chemicals / pesticides, so there is no chemical pollution of the environment / soil / water / does not harm non-target organisms / is more sustainable
- One disadvantage: the introduced species may become a pest itself / may affect other species in the ecosystem / may be difficult to control once released / biological control acts more slowly than pesticides
Key terms in this question
biological control · pesticides
Related
- All Pearson Edexcel International GCSE Biology (4BI1) revision notes →
- How to answer a "Describe" question →
- Decode the mark scheme abbreviations →