Peppered Moth Lab

Lab Objectives:

  • Describe the importance of coloration in avoiding predation
  • Relate environmental change to changes in organisms
  • Explain how natural selection causes populations to change

Background:

Industrial Melanism is a term used to describe the adaptation of a population in response to pollution. One example of rapid industrial melanism occurred in populations of peppered moths in the area of Manchester, England from 1845 to 1890. Before the industrial revolution, the trunks of the trees in the forest around Manchester were light grayish-green due to the presence of lichens. Most of the peppered moths in the area were light colored with dark spots. As the industrial revolution progressed, the tree trunks became covered with soot (chimney smoke) and turned dark. Over a period of 45 years, the

dark variety of the peppered moth became more common.

Materials

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  • Sheet of white paper
  • Newspaper
  • Forceps
  • Colored Pencils
  • Clock with Second Hand
  • 30 newspaper cutouts
  • 30 white paper cutouts

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Purpose:

______

Hypothesis:

______

Procedure

  1. You will work in a team of two. One person will be the ‘predator’ and the other person will arrange the ‘prey’ (the cutouts).
  2. Place a sheet of white paper on the table and have one person spread 30 white cutouts and 30 newspaper cutouts over the surface while the ‘predator’ isn't looking.
  3. The "predator" will then use forceps to pick up as many of the cutouts as she/he can in 30 seconds. Imagine yourself as a ‘predator’ in the wild. Repeat the trial 2 more times.
  4. Partners will then switch places so that each partner has the opportunity to be the “predator” for 3 trials total.
  5. Next use newspaper and white cutouts on a newspaper background.
  6. Similar to the steps above, each partner will now do 3 trials arranging the prey and being the “predator” on the newspaper background.

Data Table:

Starting Population / Number Remaining
Background / Newspaper / White / White / Newspaper
Trial 1 / Trial 2 / Trial 3 / Trial 1 / Trial 2 / Trial 3
Partner 1 / White / 30 / 30
Partner 2 / White / 30 / 30
Partner 1 / Newspaper / 30 / 30
Partner 2 / Newspaper / 30 / 30

Analysis: Using complete sentences, answer the following questions.

  1. What did the experiment show about how prey is selected by predators?

How did your data support this answer?

2. If the cutouts represented moths, what moth coloration is best adapted for a dark (newspaper) background?

How do you know?

3. After just one generation following the start of the industrial revolution, what would you expect the moths to look like?

  1. After 3 generations following the start of the industrial revolution, what would you expect the moths to look like?
  1. Did the experiment work in the way it was supposed to? Why/why not?
  1. Are the light and dark colored moths different species? How can you tell?

Conclusion:

Use the space below to write a minimum of a 5 sentence summary using complete sentences:

  1. What the experiment tested and showed?
  2. How the experiment relates to natural selection?
  3. How the experiment is an example of evolution (gradual change)?

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  1. Examine the table and construct a graph. Plot the years of the study on the X-axis, and the number of moths captured on the Y-axis. You should have 2 lines on your graph - one for light moths, and one for dark moths.
  1. Explain in your own words what the graph shows.

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  1. Describe how the change in moth population from dark to light could occur. What in the environment might have changed AND why?

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