Explain how speciation can occur due to geographical separation.

Mark scheme

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

1. [1] named geographical barrier; e.g. river / mountain / sea / lake
2. [1] population, separated / divided (into two);
3. [1] no, mating/breeding / gene flow, between, populations / groups;
4. [1] different (named), selection pressures / environments / conditions ;
5. [1] different mutations;
6. [1] individuals with beneficial alleles, are selected for / survive / reproduce / have a selective advantage;
7. [1] genetic drift / founder effect;
8. [1] change in, allele frequency / gene pool;
9. [1] over a long time / many generations ;
10. [1] can no longer (successfully), interbreed / reproduce / produce fertile offspring, with, old / original / other, population / species;
11. [1] allopatric (speciation);
12. [1] environment changes;
13. [1] species cannot adapt (fast enough);
14. [1] climate / temperature / sea level, change;
15. [1] extinct species / species at risk;
16. [1] competition / predation / disease, from, new / introduced / alien / invasive, species ;
17. [1] extinct species / species at risk ;
18. [1] (named) habitat, degradation / loss;
19. [1] extinct species / species at risk ;
20. [1] hunting by humans / poaching / (over)fishing ;
21. [1] extinct species / species at risk ;
22. [1] AVP;
23. [1] extinct species / species at risk ;