A-LevelBiologySelection and evolution9700/42 · Oct/Nov 2024 · Q29 Marks
2 Several different processes can affect allele frequencies in populations.
- (a)Outline the processes that may affect allele frequencies in wildlife populations.[6]
- (b)The process of selective breeding changes allele frequencies in a population. Plant breeders use selective breeding to improve crop plants such as maize. Explain how selective breeding can be used to obtain a variety of maize where the plants are vigorous and of uniform height.[3]
Mark scheme
Marking points from the official mark scheme (Oct/Nov 2024). The mark or mark type is shown in brackets.
- any six from:
- 1 mutation / described ;
- 2 genetic drift / described ;
- 3 founder effect / group separated from main population to found a new population ;
- 4 bottleneck effect / large fall in population ;
- 5 natural / directional / disruptive, selection ; Ignore artificial / stabilising selection
- 6 migration / gene flow / interbreeding between populations ;
- 7 genetic recombination / linkage groups broken / crossing over ;
- 8 AVP ; e.g. effect larger in small populations
- any three from:
- 1 inbreeding / described ;
- 2 produces homozygous plants / increases homozygosity ;
- 3 outbreeding / described ;
- 4 hybridisation / producing a hybrid ;
- 5 hybrids / offspring / F1, are (all) heterozygotes / have increased heterozygosity ;
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