∞ generated and posted on 2016.09.05 ∞
Changes in allele frequencies that occur within populations due to sampling error.
Genetic drift represents literally random changes frequencies of existing alleles found within populations over time. Generally, the fewer individuals that are found within populations then the greater the impact of genetic drift on allele frequency as measured over time.
The following video truly was the best that I was able to find on the subject of genetic drift. That's not knocking it, but instead is knocking many of the rest (yeech). Enjoy!
The impact of genetic drift tends to be non-adaptive, which is to say that genetic drift can genetically modify populations in ways that run counter to the impact of natural selection, with increases in frequencies of maladaptive alleles rather than of adaptive alleles.
Two scenarios in which genetic drift occurs are genetic bottlenecking and founder effect. Both involve the transmission of relatively few individuals within a population from generation to generation, though under different circumstances.
Video (This video presents drift, of a line! Clearly some silliness in there but makes its point nonetheless; kind of like playing 'telephone', but visual)