Evolution can be defined as the process by which the characteristics of a species undergo changes over a number of generations through the process of natural selection. There are several mechanisms that try to explain the process of evolution and these are mutation, migration, genetic drift and natural selection. However, for natural selection and genetic drift to occur, some type of genetic variation must exist. To begin with, natural selection can be defined as the process by which organisms that are best adapted to a given environment survive and produce fertile offspring. Organisms that do not appear to adapt to that particular environment are excluded. For natural selection to occur there must be a series of processes that particular organisms must exhibit and this is in accordance with Darwin's idea of ​​evolution. For starters there is trait variation. This can be seen by the fact that some organisms within a species are different from others in terms of color, size and other factors. Variations in the genes of these species determine these differences. These variations are caused by mutations that lead to the development of new alleles in a given population of a particular species. After the variation of traits there is differential reproduction. Due to the fact that the offspring produced tends to be greater than the number that can be supported by that ecological niche, the struggle for shelter, mates and food develops so that the fittest organisms are able to survive and reach maturity . After reaching maturity they can now reproduce fertile offspring who have the genetic complement of their parents. Offspring tend to inherit the traits laid down by their parents and therefore are… in the middle of the paper… if these random drifts include the bottleneck and founder effect (Coyne, 2009). Bottlenecks are known to occur when a population experiences a sharp decline due to environmentally driven factors, examples of these factors include; earthquakes, tsunamis and other natural disasters that can cause population decline. These events can lead to a situation where genetic diversity exists, thus causing the surviving population to vary widely from the original population. On the other hand, the founder effect can be defined as the loss of genetic variation due to the appearance of a new population consisting of a small number of individuals that have spread from a larger population. This leads to the prevalence of certain genetic traits since there is no genetic diversity and this can lead to the spread of genetic diseases in that particular group of individuals.