Retelling Experiments H,B,D, Kettlewell's Studies of Industrial Melanism in Peppered Moths - Essay Example

Hagen reports further that Kettlewell himself added to the controversies through his defense to these criticisms, sidelining his own singular achievements in these first attempts at understanding survival patterns in the peppered moths. This summary endorses his views tentatively and sets out to describe Kettlewell's experiments in the most likely manner. The papered moth (Biston betularia) is almost a mythical creature in evolutionary biology today because it helped practitioners solve an important mystery in evolution.

The moth, an endemic species to Great Britain and other parts of Europe, is known to have existed in three broad phenotypes. Before the industrial revolution of the 19th century the moth, popularly ascribed later as the typical phenotype, had grayish white wings flecked with small dark spots (Hagen, 1999, p. 144). Later on, with the growth of industry and increasing pollution, especially the aerial variety from coal dust in flues, in the surrounding areas this light-winged typical variety became less and less evident and moths with darker wing colors became more manifest.

The more frequent appearance of this dark phenotype (Biston carbonaria), especially in wooded regions near industrial areas, raised questions among biologists who sought to explain their strange manifestation. It is significant to note here that the carbonaria has thoroughly dark wings while intermediate varieties with varying degrees of darkness in the wing colors, Biston insularia, have been increasingly observed since the time of Kettlewell's first experiments in an wooded area near the industrial town of Birmingham (Cook and Grant, 2000).

The carbonari and insularia phenotypes are popularly known as melanics, because of their darker wings, and they evolve from activation of separate alleles available at the same locus as the typical phenotype gene, construed to be the original one (Cook and Grant, 2000).Kettlewell's Experiment:Before setting out on his first observational experiments in the woods near Birmingham, Kettlewell had already settled upon a theory in explanation of the strange higher incidence of the melanic varieties over the typical ones in that experiment area (Hagen, 1999, p.146). The first experiment here lasted for 11 days.

The environment was mixed with birch and oak trees. While the birches had relatively lighter trunk colors the oak trees tended to have trunk colors darkened with soot from the neighboring industrial regions (Hagen, 1999, p. 146). Kettlewell reported all three phenotypes of the moths existing at the site. The typical ones tended to merge with the lighter colored birches while the melanics tended to do so on the darker oak trunks. For Kettlewell, the selection hypothesis suggested that the numbers of melanics would be