Genetic Drift

Genetic drift is the process of change in genetic information in a population. It is caused by random chance or events. These random events result in changes in allele frequencies within the population.  Genetic drift is not natural selection (http://www.biology-online.org/dictionary/Genetic_drift).   Genetic drift does not allow for adaptation.  Natural selection is the force behind adaptation.  Genetic drift along with natural selection, mutation, and migration can lead to evolutionary change (http://evolution.berkeley.edu/evosite/evo101/IIIDGeneticdrift.shtml).  Genetic drift is seen more in smaller population sizes than in larger population sizes.  There are two types of genetic drift.  There is the founder effect and the bottleneck effect.  The founder effect is when a few individuals move to a new area.  This may cause there to be less genetic variation within the population being founded.  The bottleneck effect is when the population is decreases by a certain event.  For example, the events may include anything from natural occurrences, such as hurricanes, tornadoes, floods, ect., to human inflected causes, such as hunting or land/habitat destruction(http://evolution.berkeley.edu/evosite/evo101/IIID3Bottlenecks.shtml).  This website also gives a couple of examples of each type of genetic drift.  Genetic drift also may cause alleles to become fixed.  It is where only one allele is present in the population due to lack of genetic flow.  There are a few ways to keep the population from getting to the point of allele fixation or to reverse allele fixation.  People can work on rebuilding the habitat that the populations once had.  This will allow them to be better suited for their environment and allow for the population to grow in size.   After the habitat is established, new members of the species can be brought in from other areas to supply genetic variation.  If there is a barrier between two populations, a channel or pathway can be formed to allow the two populations to migrate to the other areas to allow gene flow to occur.