Variation exists in populations of a species and this may provide the opportunity for evolution to occur.

Mark scheme

Marking points from the official mark scheme (May/June 2024). The mark or mark type is shown in brackets.

1. [3] (a) 1 genetic / genotype / alleles or example ; mutation / crossing over / independent assortment / random fertilisation / random mating ;
2. [3] (a) 2 environmental or example ; climate / disease / food availability / soil pH / selection pressure ;
3. [3] (a) 3 combination / interaction, of genes and environment or example ; gene (expression) is modified by environment ;
4. [3] (b)(i) any three from:
5. [3] (b)(i) 1 formation of new species from, pre-existing species / common ancestor ;
6. [3] (b)(i) 2 change in, characteristics / phenotypes ;
7. [3] (b)(i) 3 over, time / generations ;
8. [3] (b)(i) 4 natural selection ;
9. [3] (b)(i) 5 changes in, gene pools / allele frequencies or genetic drift ;
10. [3] (b)(ii) any three from:
11. [3] (b)(ii) 1 compare sequences (of DNA) ;
12. [3] (b)(ii) 2 the more similar the sequences the more, closely related the species / recent the common ancestor ; ora
13. [3] (b)(ii) 3 over time mutations accumulate or less time fewer mutations occurred ;
14. [3] (b)(ii) 4 ref. to bioinformatics / software / database ;
15. [3] (b)(ii) 5 AVP; e.g. molecular clock / constant rate of mutation e.g. mtDNA has no crossing over e.g. the percentage similarity can be used to build a phylogenetic tree