The Moth Essay

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• The change in colour of the peppered moth after the Industrial Revolution is a classic example of evolution in action.
• When newly industrialised parts of Britain became polluted in the nineteenth century, smoke killed lichens growing on trees and blackened their bark. Pale coloured moths which had been well camouflaged before when they rested on tree trunks became very conspicuous and were eaten by birds. Rare dark moths, which had been conspicuous before, were now well camouflaged in the black background. As birds switched from eating mainly dark moths to mainly pale moths, the most common moth colour changed from pale to dark. Natural selection had caused a change in the British moth population. The moths had evolved.

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Answer 1

• the most common variety of the peppered moth in england was a mottled gray color. During the day, as moths rested on lichen-covered tree trunks, their coloration provided camouflage. There was also a dark gray variety of the same species, but because the dark moths were not as well camouflaged, they were more frequently eaten by birds and so they were less common. (in this example the birds are the selective agent, and they apply selective pressures on the moths).

yet by the end of the nineteenth century, the darker form had almost completely replaced the common gray one. The cause of this change was the changing enviroment of industrialized nineteenth century england. coal dust from the factories and fireplace settled on the trees, turning them dark gray and killing the lichen.

The moths continued to rest on the trees, but the light gray ones became more conspicuous as the trees became darker and they were increasingly targeted by birds. Fewer of the light gray moths were living long enough to reproduce, so they contributed fewer genes to the next generation than the darker moths did, and the proportion of lighter moths decreased while the dark moths became more common. The kind of evolutionary shift in response to enviromental change is called adaptation

Selective pressures- Forces in the enviroment that influence reproductive success in individuals

adaptation- An anatomical, physiological, or behavioural response of organisms or populations to the enviroment. Adaptations result from evolutionary change (specifically, as a result of natural selection).