Chance events can affect the subsequent evolutionary history of populations. Ex: When a storm blows insects or birds hundreds ofkm oveer an ocean to an island, the wind doesn't necessiarly transport those individuals that are best suited to the new environment. Thus, not all alleles present in the founding population's gene pool are better suited to the new environment than the alleles that are "left behind." In addition, the environment at a particular location may change unpredictably from year to year, again limiting the extent to which adaptive evoltuion results in a close match between the organism and current environmental conditions.
chance, natural selection, and the enviironment interact