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Natural Selection

Natural selection is one of the basic mechanisms of evolution, along with mutation, migration, and genetic drift (Berkeley) It is a process in nature in which organisms possessing certain genotypic characteristics that make them better adjusted to an environment tend to survive, reproduce, increase in number or frequency, and therefore, are able to transmit and perpetuate their essential genotypic qualities to succeeding generations. This theory was put forward by Charles Darwin, trying to explain how evolution of species occurs.

Look at an example to help make the concept natural selection clearer: 

Industrial melanism is a phenomenon that affected over 70 species of moths in England. It has been best studied in the peppered moth, Biston betularia. Prior to 1800, the typical moth of the species had a light pattern. Dark colored or melanic moths were rare and were therefore collectors' items.During the Industrial Revolution, soot and other industrial wastes darkened tree trunks and killed off lichens. The light-colored morph of the moth became rare and the dark morph became abundant. In 1819, the first melanic morph was seen; by 1886, it was far more common -- illustrating rapid evolutionary change. Eventually light morphs were common in only a few locales, far from industrial areas. The cause of this change was thought to be selective predation by birds, which favored camouflage coloration in the moth.

The following is a quote from Charles Darwin :
"Variation is a feature of natural populations and every population produces more progeny than its environment can manage. The consequences of this overproduction is that those individuals with the best genetic fitness for the environment will produce offspring that can more successfully compete in that environment. Thus the subsequent generation will have a higher representation of these offspring and the population will have evolved."



From:http://image.slidesharecdn.com/topic4-130917213109-phpapp01/95/summary-of-topic-41-biodiversity-in-ecosystems-15-638.jpg?cb=1379967830
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