Mitosis to produce a larger population
Meiosis is the process of dividing a diploid cell into haploid cells. The main results of meiosis are four haploid cells. Genetically, these cells differ from the diploid cell and from each other.
A natural disaster can reduce the population size of a species, leading to a random fluctuation in allele frequencies due to chance rather than natural selection. This can cause some alleles to be lost and others to become more common, leading to genetic drift. Over time, this can result in changes to the genetic diversity of the population.