Evolution and Adaptation to the EnvironmentVariation allows some individuals within a population to adapt to the changingenvironment. Because natural selection acts directly only on phenotypes, more geneticvariation within a population usually enables more phenotypic variation. Some new allelesincrease an organism’s ability to survive and reproduce, which then ensures the survivalof the allele in the population. Other new alleles may be immediately detrimental (such asa malformed oxygen-carrying protein) and organisms carrying these new mutations willdie out. Neutral alleles are neither selected for nor against and usually remain in thepopulation. Genetic variation is advantageous because it enables some individuals and,therefore, a population, to survive despite a changing environment.Genetic variation in the shells of Donax variabilis: An enormous amount of phenotypicvariation exiss in the shells of Donax varabilis, otherwise known as the coquina mollusc.
