Describe the process of selective breeding that a farmer could use to produce a herd of cattle with a higher milk yield.

Pearson Edexcel International GCSE Biology (4BI1) — 5.2 Selective breeding · Describe · 4 marks · View as Markdown

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

A farmer has a herd of cattle that produce varying amounts of milk. The farmer wants to use selective breeding to increase the milk yield of the herd over several generations.

Model answer (4 marks)

1. Identify the cows that give the highest milk yield in the herd.
2. Allow only those high‑yielding cows to breed with each other.
3. From the next generation, select the offspring that also give the highest milk yield.
4. Repeat steps 2–3 over several generations.
5. After many generations, the herd will show a higher average milk yield.

Examiner tips

Use the word ‘identify’ for the first step, ‘breed’ for the second, and ‘select’ for the third.
Show the cycle of selection and breeding clearly – a short list is fine.
Mention that the process is repeated over several generations to achieve the result.
Use UK spelling (e.g., ‘breed’ not ‘breeding’).

Common mistakes

Writing ‘breed all cows’ instead of only the high‑yielding ones.
Forgetting to state that the process is repeated over several generations.
Using vague terms like ‘improve’ without describing the selection steps.

Mark scheme (4 marks)

Identify and select cattle with the highest milk yield / desirable characteristic from the existing herd
Breed the selected cattle with each other / allow the selected individuals to reproduce together
Select offspring with the highest milk yield from the next generation and breed them again / repeat the selection and breeding process over several generations
Over time / after many generations, offspring will show the desirable phenotype / higher milk yield

Key terms in this question

selective breeding