Within a population there is genetic variation between individuals. For example, individuals have different combinations of different alleles, which may or may not be passed onto their offspring. Genetic drift is a change in the frequency of different alleles within the population as a result of chance. Genetic drift is more important in small populations because the chances of an allele being lost or fixed in the population are much higher, this is because each individual in a small population represents a larger proportion of the entire population (than in a large population).For example; in a population of 20 individuals (n=20), 10% of the population carry allele A. Therefore, 2 individuals carry A (20/10 = 2), thus only 2 individuals need to die, not reproduce, or not pass on allele A to their offspring for it to be lost from the population. Meanwhile in a population of 2000 individuals (n = 2000), if 10% carry allele A, that's 200 individuals (2000/10 = 200) that have to unsuccessfully pass on A for it to be lost from the population. So, the chances of A being lost via genetic drift, is much more likely in the small population (n=20).
Explain why genetic drift is more powerful in small populations.
Genetic drift is a mechanism of evolution in which allele frequencies of a population change over generations due to chance (sampling error). Genetic drift occurs in all populations of non-infinite size, but its effects are strongest in small populations.
why does genetic drift affect smaller populations more than larger populations? smaller populations are more affected by any change in allele frequency as they will be a greater proportion of the population. they have lower genetic diversity as there are fewer alleles so change will have a greater influence.