Natural Selection- A Case StudyName: ______________________________ Date: ________________ Hour: ____

Four main principles are involved in the basis of the theory of natural selection. What are they?

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Case Study: The Peppered Moth ! Peppered moths, a species of moth which lives predominantly in England, have undergone visible natural selection since the late 1700s. Up until the late 1700s, the moths were primarily speckled white in color with some moths having a darker pattern. As more moths were born each year, light-speckled moths became more common in the population, because they were better able to blend into the tree trunks where they rested. This prevented them from being eaten by birds that preyed on them in the woods. However, the mid-1700s marked the beginning of the Industrial Revolution in England. As machinery began to be used regularly near the mothsʼ habitat, the trees became darker with soot. As the mothsʼ environment changed, the alleles that were common in their population began to change! Complete the activity below to view a demonstration of how the effects that followed occurred.

Materials:! -White hole punches (1 bag per group)" -Newspaper hole punches (1 bag per group)" -One sheet of paper (handed out by the instructor)" -1 Pair of Tweezers

Instructions:1. Place your sheet of paper on the table, and have one person spread 20 white hole punches and

20 newspaper hole punches over the surface while the other person isnʼt looking. 2. The other person (the “predator” or bird) will then turn around and pick up the first hole punch

that they see. They have “killed” this moth, and will remove the hole punch from the rest of its population (set it aside)

3. Record the number of hole punches of each type in the table below before continuing!4. Once the final population is recorded, double the number that remain to represent the fact that

because those individuals survived, they can reproduce. Follow the math in the table, which is bolded and in italics.

5. Continue this process for 4 generations, recording the number of individuals left after each round of selection and reproduction. Repeat this process on a sheet of newspaper and see how your results change!

6. Be sure to fill out which paper you used (white or newspaper) in the space above your table.

**____________** Paper:Generation Starting PopulationStarting Population Number CapturedNumber Captured Final PopulationFinal PopulationGeneration

Newspaper White Newspaper White Newspaper White

1 A. 20 B. 20 C. D. A-C=E.

B-D=F.

2 Ex2=G.

Fx2=H.

I. J. G-I=K.

H-J=L.

3 Kx2=M.

Lx2=N.

O. P. M-O=Q.

N-P=R.

4 Qx2=S.

Rx2=T.

U. V. W. X.

7. Meet with a member of a group that used the opposite type of paper background that you did. Use the space below to write out (in your own words) the trends that they saw in their final populations.

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Questions for Thought: 1. Describe how the population of moths changed between generations 1 and 4 for the moths in

the newspaper environment. ________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

2. Describe how the population of moths changed between generations 1 and 4 for the moths in the white paper environment.

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3. Different species have traits that make them well suited to certain environments. Some examples of adaptations are giraffesʼ long necks, for eating out of tall trees, and batsʼ ability to navigate in the dark by making noises and listening to how the sound waves echo off of other objects. Biologists call these advantageous traits “adaptations.” How do scientists explain how adaptations occur? (HINT: Look back at your four main principles! How does variation enter a population?)

________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________4. What moth coloration is the best adaptation for the dark (newspaper) background? Give data

from your table or your observations in #7 that supports your answer.________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

4. How does this simulation model natural selection? Describe where the four principles of natural selection can be found in this model.

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5. Examine the table below and construct a graph of it at right. Plot the years of the study on the x-axis and 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. (Make sure to label your axes and give the graph a title and axis units!)

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Explain, in your own words, what the graph shows. What type of environment do you think these moths live in? Why?__________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

Year # of light moths captured

# of dark moths captured

1 540 110

2 480 200

3 390 210

4 250 280

5 220 340

6 190 410

7 150 500

8 90 550