What is the difference between genetic dift and natural selection?

Genetic drift and natural selection are similar in that they are both related to the process of Evolution, however they are fundamental different. Genetic drift occurs when the allelic frequencies of a population randomly change due to probability or chance. This occurs more often in small populations. As a metaphor, think about when you flip a coin. The probability of getting ?heads? when you flip a coin is 0.50. However, if you flip the coin three times, you may see ?heads? three times, which would result in the observed probability 1. The more times you flip the coin, the closer your observed probability will get to 0.50. Similarly, the larger the population you have in an area, the closer your allelic frequency would be to the ?true? allelic frequency.

Natural selection, on the other hand, is a non-random evolutionary process. It occurs when a phenotype becomes more common in a population because a trait gives an organism an advantage over another organism. For example, say you have a population of bunnies in a given area, some are fast, some are slow. In this area, there are predators who prey on the bunnies. The faster bunnies who out run the predators, are more likely to survive to reproductive age and pass on their genes.