A breeder produced sunflowers with a high oil yield by selecting a small number of plants and breeding their offspring together for 12 generations.
Scientists compared the selectively bred line with an unselected population. Both populations were exposed to a new disease.
| Population | Total number of different alleles detected at 12 genes | Plants that survived the disease in % |
|---|---|---|
| Unselected population | 41 | 84 |
| Selectively bred line | 17 | 27 |
Which statement best explains both results for the selectively bred line?
Selective breeding reduced the range of alleles, so fewer plants were likely to have an allele for resistance.
The bred plants changed their own alleles to make more oil, so fewer plants kept alleles for resistance.
Breeding for high oil yield left each plant with fewer genes, so fewer plants had a gene for resistance.
Breeding for high oil yield caused mutations that removed alleles, so fewer plants could resist the disease.
80 exam-style questions on AQA GCSE Biology 6.2 Variation and evolution, covering 6.2.1 Variation, 6.2.2 Evolution, 6.2.3 Selective breeding, 6.2.4 Genetic engineering, and 6.2.5 Cloning. Each one has a worked solution and a mark scheme showing where the marks go.