Humans use selective breeding to improve the features of crop plants and domestic animals.

Mark scheme

Marking points from the official mark scheme (May/June 2021). The mark or mark type is shown in brackets.

1. [1] artificial selection;
2. [1] (humans) choose / cross / breed from, females / cows / cattle, with, good / high, milk yield;
3. [1] (humans) choose / cross / breed from, males / bulls, with, mother / sisters / daughters, with, good / high, milk yield ;
4. [1] (humans) choose / cross / breed from, desirable offspring;
5. [1] continue / repeat, for (several) generations ;
6. [1] allele(s) for, high milk yield / desired trait, passed on;
7. [1] increase in frequency of, good / best / high yield, allele(s);
8. [1] artificial insemination / A.I. ;
9. [1] AVP;
10. [1] mean/mode/ median / average / intermediate, selected against / not favoured / less fit / die ;
11. [1] (both) extremes, selected for / favoured / more fit / survive / reproduce;
12. [1] bimodal distribution;
13. [1] diversifying selection ;
14. [1] causes / maintains, polymorphism / genetic diversity ;