Chelsea Borek
Kerr
EN101-5
10-27-10
Peppered Moth Evolution
As humans have evolved, they have often impacted the environment of other organisms. The peppered moths have proven to be an excellent subject for this observation because scientists have noticed an adaptation resulting from a change in their environment created by human activity. The moth gets its name from the scattered dark markings on its wings and body. The scientific name for the peppered moth is Biston Betularia. This moth is nocturnal and rests on tree trunks that are encrusted with white lichens during the day (“Biston Betularia”). Their markings make them almost invisible against the tree trunks. Occasionally, a moth would be born with a darker colorization. This type of moth was so visible when it landed on the trees they were readily caught and eaten by birds. This prevented the darker colored moth from reproducing and reduced the dark color in the gene pool. The camouflage of the peppered moth population changed in the nineteenth century due to the industrial revolution, natural selection, and evolution.
After the Industrial Revolution there was a noticeable decrease in light colored moths and an increase in dark ones. The Industrial Revolution started in England in the eighteenth century and is defined as the era of the replacement of manual labor by machines. Around this time, there was an increase in the human population and an increase in inventions to make their work easier and more efficient (“Industrial Revolution”). As new inventions were being created, there was a subsequent increase in factories. The factories at this time used coal as the main source of energy, and when coal is burned, carbon particles are released into the atmosphere (Smith, Harry). The result of the burgeoning number of factories was that they created layers of soot that covered the light colored trees and tuned them dark grey, altering the external environment of the peppered moths.
With the change in environment, the light colored moths were more visible to the predators and the dark moths were camouflaged. Since the dark moths were now effectively hidden from the birds, they survived long enough to reproduce and pass on the dark color genes to their offspring. This change in camouflage is a classic example of adaptation through natural selection. Natural selection occurs when a population has varying genotypes, or genetic DNA combinations. Some of these variations are inherited by offspring and show in the phenotype, or the offspring’s appearance. The offspring with the best camouflage in its environment is most likely to survive and reproduce, thus passing on their genes to another generation (Kimball). The light colored moths were being eaten more because their camouflage was no longer effective in the new darker environment. Because of the pollution created during the Industrial Revolution, the darker moths had better camouflage against the soot covered trees. These darker moths were able to reproduce and pass on their fit genes to their offspring and effectively increase the dark colored genes in the gene pool (“IV”).
The increased number of genes coding for dark color in the peppered moth led to a natural selection of the dark color over the lighter color. Over time, natural selection results in an evolutionary change in a species. An evolution is a process that results in genetic changes in a population seen throughout generations. The evolution of the peppered moths resulted in a decrease in the population of the light colored moths, and an increase in the population of the darker moths. This evolution of change occurred over a span of many generations and created a new camouflage for the peppered moths. According to Douglas Futuyma, "… evolution is merely change… Biological evolution ... is change in the properties of populations of organisms that transcend the lifetime of a single individual. The ontogeny of an individual is not considered evolution; individual organisms do not evolve. The changes in populations that are considered evolutionary are those that are inheritable via the genetic material from one generation to the next. Biological evolution may be slight or substantial; it embraces everything from slight changes in the proportion of different alleles within a population…” (Morgan, Laurence).
Evolution is a process that occurs both naturally and accidentally. In the case of the peppered moth, the evolution was accidental due to human activity during the Industrial Revolution. The Industrial Revolution caused a change in the moth’s environment, resulting in a natural process referred to as natural selection. The effect of this was an evolution of color change in the moth from light to dark. Evolution is an ongoing process. Since pollution abatement programs were put in place after World War II, the light form of the peppered moth has been making a comeback (“A History”). With these programs, humans are causing yet another change in the habitat of the peppered moths that may lead to another evolutionary change.
Works Cited
"Biston Betularia - Definition." Dictionary, Encyclopedia and Thesaurus - WordIQ Dictionary. Web. 18 Oct. 2010. <http://www.wordiq.com/definition/Biston_betularia>.
"A History of the Architecture of the USDA Forest Service (Chapter 1)." The Forest History Society. 8 June 2008. Web. 24 Oct. 2010. <http://www.foresthistory.org/ASPNET/Publications/architecture/chap1d.htm>.
"Industrial Revolution: Information Page." Oracle ThinkQuest Library. Web. 19 Oct. 2010. <http://library.thinkquest.org/4132/info.htm>.
"IV. Natural Selection; or the Survival of the Fittest. Illustrations of the Action of Natural Selection, or the Survival of the Fittest. Darwin, Charles Robert. 1909-14. Origin of Species. The Harvard Classics." Bartleby.com: Great Books Online -- Quotes, Poems, Novels, Classics and Hundreds More. Web. 21 Oct. 2010. <http://www.bartleby.com/11/4003.html>.
Kimball, J. "Evolution and Adaptation." Kimball's Biology Pages. Harvard University, 25 Aug. 2010. Web. 18 Oct. 2010. <http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/E/Evolution.html>.
Morgan, Laurence. "What Is Evolution?" The Talk Origins Archive. 22 Jan. 1993. Web. 20 Oct. 2010. <http://www.talkorigins.org/faqs/evolution-definition.html>.
Smith, Harry L. "The Environment Since the Industrial Revolution." Welcome to The Future of Freedom Foundation. 1993. Web. 19 Oct. 2010. <http://www.fff.org/freedom/0993d.asp>.
