The graph shows two simulations starting at allele frequency 0.5 in small populations. The two outcomes (one fixed, one lost) are examples of
- Acheck_circle
Genetic drift — random sampling can fix or lose alleles especially in small populations
- B
Migration — gene flow between populations rapidly fixes or removes alleles by chance
- C
Mutation — new variants arise randomly and either reach fixation or disappear from the gene pool
- D
Natural selection — fitness differences consistently favor one allele over the other
Explanation
With no selection, drift can drive alleles to fixation or extinction by chance. The smaller the population, the larger the fluctuations.