Biston Betularia

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Industrial Melanism of Biston Betularia or the Peppered Moth in England has been a textbook example of natural selection since it was first noticed. Before the industrial revolution the peppered moth was most commonly found in the light colored Typica variety. During the industrial revolution there was a significant rise in the dark Carbonaria form and a slight rise in the intermediate Insularia form. Beginning in 1970 the Typica variety has been rising in frequency again. Carbonaria went from an estimated 95% of the population down to 5%.(Cook et al 1986) This change has been assumed to be caused by increased predation on moths that did not blend into the bark of trees (Cook et al 2012). Before the industrial revolution the trees were light …show more content…
Over six years, four thousand eight hundred sixty-four moths were released onto locations that Majerus had proven to be normal resting places. An average of less than ten moths were released a night. Any moth missing from its resting point four hours after sunrise were considered to be eaten since peppered moths do not frequently fly during the day. He found that the ratio of varieties eaten per year were relatively the same across the experiment. There was great selection in his experiment against Carbonaria with a p value of 0.003. He found a selection pressure against Carbonaria of one tenth to two tenths per generation. Since the average life span is only a few days this would make for a rapid change in populations. Majerus directly observed that one quarter of the disappearances were bird predation. He did not witness the other disappearances but was able to conclude that other factors on survival were negligible. (Cook et al 2012) Majerus’ results make it difficult to disbelieve the industrial melanism in Biston Betularia is due to anything but natural selection. He successfully showed that many of the criticisms of Kettlewells’s work were answered. He also found some new and accurate data with his very carefully collected data. Both Kettlewell and Majerus found that the Carbonaria had a higher survival rate in polluted forests and Typica had I higher rate of …show more content…
This is not only because of the theoretical importance which can be taught by many other examples that have less debate over the cause, but because of how easy the example is to teach natural selection. The example is relatively simple and easy to visualize. It is easy to see that the difference in the forms which is caused by a Single Mendilian inheritance, bird predation, and the effects of pollution on the trees. Because the example is clear and easy for people with little to no science training to understand, Industrial melanization will remain a steady teaching tool for a long time to come. (Rudge

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