The Peppered Moth

Natural Selection

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All About The Peppered Moth or Darwin's Moth

Peppered Moths are normally white with black speckles across the wings, giving it its name. This pattern makes it well camouflaged against lichen-covered tree trunks when it rests on them during the day. There is also a naturally occurring genetic MUTATION which causes some moths to have almost black wings. These black forms are not as well camouflaged on the lichen as normal 'peppered' forms and so they are more likely to be eaten by birds and other predators. This means that fewer black forms survive to breed and so they are less common in the population than the paler peppered forms.

Natural Selection

Natural selection is one of the basic mechanisms of evolution, which Darwin proposed as a simple but often misunderstood idea. For natural selection to occur there needs to be:

  1. variation within a population. (Industrial revolution- changes tree colour)
  2. organisms compete for limited resources. (Black peppered moths vs. white peppered moths)
  3. more offspring than can be supported. (More black trees= too many white moths)
  4. organisms with favourable characteristics survive to reproduce. (More black trees=more black moths)
  5. traits are passed on from one generation to the next as genetic information. (More and more black peppered moths breed, white are dying from natural selection)

As a result, over successive generations, the black moths came to outnumber the pale forms in towns and cities. Since moths are short-lived, this evolution by natural selection happened quite quickly. For example, the first black Peppered Moth was recorded in Manchester in 1848 and by 1895 98% of Peppered Moths in the city were black.

Natural Selection - Peppered Moth
Natural Selection Game of The Peppered Moth

This game is what was in the video above. It shows what happens to peppered moths from natural selection.

Charles Darwin

Charles Robert Darwin, born 12 February 1809 – 19 April 1882, was an English naturalist and geologist was best known for his contributions to evolutionary theory. He established that species came from common ancestors. Darwin used finches on the Galapagos Islands to help prove his theory of natural selection. By looking at all the different types of finches he came to the conclusion of them coming from a common ancestor.

Dr Bernard Kettlewell

Doctor Bernard Kettlewell, born 24 February 1907- 11 May 1979, was a British Genetiicist, lepidopterist, and medical doctor. He performed research on the influence of industrial melanism on the peppered moth colour change. His experimentations proved a classic example of natural selection.