Selective breeding is used by farmers to improve crop plants. Explain how a farmer could use selective breeding to produce a wheat crop that consistently gives a high yield over several generations.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Farmers have been using selective breeding for thousands of years to improve the characteristics of crop plants. A farmer wants to develop a variety of wheat that reliably produces a high yield of grain each harvest.
Model answer (5 marks)
Identify wheat plants that give a high yield in the current crop.
Select only those high‑yield plants to breed (allow them to cross‑pollinate).
Harvest the seeds from these plants and grow the next generation.
From the new crop, again choose the plants that give the highest yield.
Repeat this selection and breeding over many generations.
After several generations the high‑yield trait becomes common, so the wheat consistently produces a high yield.
Select only those high‑yield plants to breed (allow them to cross‑pollinate).
Harvest the seeds from these plants and grow the next generation.
From the new crop, again choose the plants that give the highest yield.
Repeat this selection and breeding over many generations.
After several generations the high‑yield trait becomes common, so the wheat consistently produces a high yield.
Examiner tips
- Use the word ‘select’ and ‘breed’ to show the process. Show the cycle of selection → breeding → new generation. Mention that the trait becomes more common over time.
- Include the key phrase ‘high yield’ as the desired characteristic.
Common mistakes
- Not specifying that only high‑yield plants are chosen for breeding. Failing to mention that the process is repeated over many generations. Using vague terms like ‘improve’ without describing the selection steps.
Mark scheme (5 marks)
- Identify plants from the existing population that show the desired characteristic (high yield)
- Allow only these selected plants to breed together / cross-pollinate
- Select offspring that show the highest yield from the next generation
- Repeat the process over many generations
- Over time the desired characteristic (high yield) becomes more common / the plants consistently produce a high yield because the alleles for high yield are passed on to offspring
Key terms in this question
selective breeding · generation
Related
- All Pearson Edexcel A-Level Biology A (9BI0) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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