Natural selection: where the pressures of environmental selection confer a selective advantage on a specific phenotype to enhance its viability and fecundity.
Ummm, thanks QCAA.
Simpler translation: Certain characteristics you already have may become advantageous if the environment changes, leading to your survival and ability to reproduce.
Linking Genetic Drift and Natural Selection
Natural selection is like genetic drift but with one major difference—it’s not random.
Unlike genetic drift which can be helpful, detrimental, or have no effect, natural selection represents only positive change/adaptation. Out of all the mechanisms of evolution, it’s the only one that can consistently make populations adapted, or better-suited for their environment, over time. Natural selection is influenced by changes in environmental conditions while genetic drift is random and based on luck.
Natural selection acts on an organism’s phenotype which is a product of genotype. When a phenotype produced by certain alleles helps organisms survive and reproduce better than their peers, natural selection can increase the frequency of the helpful alleles from one generation to the next – that is, it can cause microevolution (small-scale variation of allele frequencies within a species or population, in which the descendant is of the same taxonomic group as the ancestor).