Directional Selection - Biology, Esquemas y mapas conceptuales de Biología

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Directional

selection

Sofía Beltrán, Romina Espinoza, Anahí Mancheno,

Luisa Montiel, Diego Obando y Valeria Sánchez.

INTRODUCTION Charles Darwin was the first to describe directional selection as a form of natural selection in his foundational 1859 work On the Origin of Species. The directional selection theory says that an extreme phenotype is favored over other phenotypes and this causes the allele frequency to shift over time in favor of the extreme phenotype. In other words, if a particular trait is favorable, it will be expressed at the most beneficial frequency in the population.

EFFECTS ON THE ENVIRONMENT Directional selection is the process that comes most easily to mind when thinking about natural selection, and it is the form of selection that has taken place in the best-known examples of evolution. However, directional selection does not always result in evolution, because it can be constrained in many ways. Directional selection does the “heavy lifting” of evolution by tending to move the trait mean toward the optimum for the environment. It results in increased adaptedness of organisms. It is the principle process that Charles Darwin himself envisaged as driving adaptive evolution.

If directional selection acts in different directions in different populations or species then it is described as divergent. This results in populations becoming different, and it can contribute to speciation. It can also be artificially imposed, and it has commonly been used by animal and plant breeders to improve traits in domesticated organisms, as well as to better understand evolution. This bibliography first deals with natural directional selection, and then moves on to address artificial selection.