Response posts:
- The response to a fellow student should be a substantive evaluation of how they can improve their process of inquiry. For example, in the chapter 2 exercise, students will develop a reasoned judgment in step five. Students can help each other refine their judgments by providing suggestions for improvement or simply a different way of looking at the process.
- The response posts should be about 250 words and include: a clear description of the improvement, an example demonstrating the improvement, and a brief justification as to why it is an improvement.
Rebecca Snead
22 hours ago, at 6:24 PM
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Bernard Kettlewells peppered moth experiment is one of the most well-known examples used to explain natural selection. In the 1950s, Kettlewell studied the peppered moth in England. Before the Industrial Revolution, most peppered moths were light-colored with speckles, which helped them blend into lichen-covered trees. However, during the Industrial Revolution, pollution darkened tree bark by killing lichens and covering trees in soot. Around this time, a darker form of the moth became more common. Kettlewell wanted to test whether natural selection explained this shift in color.
Kettlewell conducted experiments where he released both light and dark moths into polluted and unpolluted forests. He then observed which moths were eaten more often by birds. In polluted forests with darker trees, light moths were more visible and were eaten more frequently. In cleaner forests, dark moths were more visible and eaten more often. Based on this, Kettlewell concluded that bird predation was the main cause of the color change in the moth population. He believed this demonstrated natural selection in action because the moths that were better camouflaged were more likely to survive and reproduce (Majerus 2009).
However, later scientists questioned some parts of Kettlewells experiment. One major critic was Theodore David Sargent, and later Judith Hooper discussed these criticisms in her book Of Moths and Men. Critics argued that Kettlewell may have placed moths on tree trunks in unnatural positions and that moths do not normally rest in such exposed spots. They suggested that his methods may have influenced the results. Some also questioned whether bird predation alone was enough to explain the rapid shift in moth color (Hooper 2002). These critiques raised concerns about whether the original conclusion was fully supported by the data.
Despite the criticisms, more recent research has strengthened Kettlewells original idea. Michael Majerus conducted a long-term study observing moth behavior in more natural conditions. His findings supported the idea that bird predation played a significant role in the color change (Majerus 2009). When thinking about the characteristics of scientific inquiry, Kettlewells hypothesis was clearly testable because it made a specific prediction: more visible moths would be eaten more often. It also offered a causal explanation by connecting environmental change (pollution) to survival differences caused by predation. Even though his methods were criticized, the fact that other scientists re-tested the idea shows the importance of peer review and replication in science. Science is not about being perfect the first time; it is about being open to correction and further testing.
In my opinion, Kettlewells conclusion is still the best explanation for the color change in peppered moths. The explanation is causal because it connects environmental pollution, camouflage, predation, and survival in a logical chain. It is also fruitful because it led to further studies that expanded our understanding of natural selection. Even the critiques helped strengthen the theory by encouraging better-designed experiments. For example, Majerus improved on earlier methods and confirmed that natural selection was occurring. That process reflects how scientific knowledge develops over time.
Overall, the peppered moth case is a strong example of how scientific inquiry works. A hypothesis is proposed, tested, criticized, and tested again. Even when flaws are found, the process of peer review and replication helps refine conclusions. While Kettlewells methods were not perfect, the overall evidence supports his main conclusion that natural selection driven by bird predation explains the color change in the moths.
Works Cited
Hooper, Judith. Of Moths and Men: Intrigue, Tragedy, and the Peppered Moth. W.W. Norton, 2002.
Majerus, Michael E. N. Industrial Melanism in the Peppered Moth, Biston betularia: An Excellent Teaching Example of Darwinian Evolution in Action. Evolution: Education and Outreach, vol. 2, no. 1, 2009, pp. 6374.
Sargent, Theodore D., et al. Evolution of Melanism: A Critique of the Classic Experiment. Biology and Philosophy, vol. 13, 1998, pp. 2954.
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