Natural Selection

Natural Selection

In order to examine the mechanism of evolution, one must first investigate four main causes to microevolution; Genetic drift, Gene flow, Mutation, and Selection. Evolution is a change in a population's frequencies of alleles from generation to generation. Alleles are an alternative form a gene. Genetic drift occurs when chance events and accidents such as earthquakes, floods and fires remove alleles from a larger population, and leaving a much small population. This reduction in size is generally called the bottleneck effect, which reduces the overall genetic variability in a population. Gene flow, formerly known as migration, can bring new alleles into a population through immigrating organisms. A population may gain or lose alleles when individual move from one community to the next. Gene flow has become an important representative in evolution.

Mutations are changes made in an organisms DNA. Mutation allows for new alleles to be created from old ones. This gene duplication event provides the opportunity for genes to be repurposed. Mutation in itself serves a useful purpose and is essential to evolution because it is the original source of genetic variation for Natural Selection.

. Natural selection is the key mechanism of evolution. It is believed that Alleles provide their owners with traits that increase or decrease fitness (the contribution an individual makes to the gene pool or the next generation, relative to contributions of other individuals), which causes an increase or decrease in the population. (p.263) Natural selection promotes adaptation, and such adaptation is the blend of chance and sorting in random generation of genetic variability. (p.264)

Reference

Campbell, Reece & Simon. (2007) Essence of Biology with Physiology. San Francisco: Pearson/Benjamin Cummings. Retrieved information of September 9, 2009

O'Neil D (1998) Early Theories of Evolution: Dawin and Natural Selection. Retrieved on September 10, 2009 from http://anthro.palomar.edu/evolve/evolve_2.htm