Name: _______________________________
Date: ________________
How is the peppered moth evidence of natural selection over a short period of time?
Lab # ______
Step 1- Background information:
Charles Darwin collected a large amount of facts to create the theory of evolution by natural selection. Darwin described
natural selection as the “process by which the organisms that are best adapted to a specific environment survive and produce
more offspring than organisms that are not as well adapted”. One of his difficulties in proving the theory, however, was the lack
of an example of evolution over a short period of time, which could be observed during ones lifetime. Although Darwin was unaware
of it, remarkable examples of evolution, which might have helped to persuade people of his theory, were in the countryside of his
native England. One such example is the evolution of the peppered moth, Biston betularia.
1)
Describe Darwin’s theory of natural selection in your own words.
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2)
What was one difficulty Darwin had supporting his theory, even though he had tremendous (large) amounts of evidence?
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3)
Why was his theory so difficult to prove?
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4)
What species was evolving rapidly in England that could support his theory of evolution by natural selection?
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Step 2- Read the following captions and carefully make observations about the pictures to help you
answer the accompanying questions.
Before the year 1845, in the city of Manchester, England a population of light gray colored moths known as Peppered moths
lived in the surrounding forests. They would cling to the trunks of trees that were covered with a light gray colored bark, like them.
1. Light gray peppered moth
*See COLORED pictures
2. Light gray colored bark
3. Light gray peppered moth
on the light gray colored tree
5)
What color are the peppered moths on the previous page? _____________________________________________________
6)
7)
What color are the trees that the peppered moths often cling to? ________________________________________________
Why do you believe the peppered moths often cling to the trees in this area?
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8)
If the color of the tree were to change, would this affect survival rate of the peppered moth? Why or why not?
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Step 3- Read the following captions and carefully make observations about the pictures to help you
answer the accompanying questions.
As a result of random mutation, populations of black peppered moths began to
appear. The black moth populations remained very low and were often never seen. The
picture on the right shows a black peppered moth on the same type of trees that the light
peppered moths often cling to.
4. Black peppered moths
Mutation: any change in an organism’s DNA
9)
Using the information, and the picture above, why do you think the population
sizes of the black peppered moths are much smaller than the light gray
peppered moths?
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Step 4- Read the following captions and carefully make observations about the pictures to help you
answer the accompanying questions.
Around 1845 the city started becoming more industrialized with factories pouring black coal smoke into the air. This pollution fell
into the surrounding forests. The pictures below show the factories and their effect on the appearance of the trees during this
period.
5. Factories polluting the air
10)
11)
6. The black and light gray peppered
moth on the polluted trees.
During industrialization, what color did the light grey barks of the trees turn? (Compare pictures 5 & 6)
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Which color peppered moth will be more likely to survive during the industrial time period? Why?
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Step 5- Read the directions below to complete a simulation of what really occurred in
England during industrialization.
Directions:
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Pick up one computer for you and your partner.
Go to http://www.techapps.net/interactives/pepperMoths.swf
Click the first circle on the right (Birds Eye View)
Read through the directions. (Partner # 2)
Before clicking on the “light forest”, complete the hypothesis below: (both partners 1 and 2)
Hypothesis: If the forests are light colored then the _________________________ colored moths will
be more likely to be eaten.
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Click on the “light forest” and partner # 1 will complete the activity.
Partner # 2; Record the percentage of light and dark moths that survived in the data table below.
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Click on the yellow circle on the bottom of the page.
Read through the directions. (Partner # 1)
Before clicking on the “dark forest”, complete the hypothesis below: (both partners 1 and 2)
Hypothesis: If the forests are dark colored then the _________________________ colored moths will
be more likely to be eaten.
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Click on the “dark forest” and partner # 2 will complete the activity.
Partner # 1; Record the percentage of light and dark moths that survived in the data table below.
Type of Forest
12)
Percent Dark Moths Survived
Percent Light Moths Survived
Light Forest
(Normal)
%
%
Dark Forest
(During and After
Industrialization)
%
%
On your own, describe your results found in the data table above and explain why these results
make sense.
The results in the data table above illustrate that in the light forest, ____________ % of dark moths and _________ % of
light moths survived. This makes sense becasuse … _______________________________________________________
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The results in the data table above illustrate that in the dark forest, ____________ % of dark moths and _________ % of
light moths survived. This makes sense becasuse …________________________________________________________
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13) Complete the Exit Slip on the back and hand in your lab when you are finished.
Name: _________________________________________
Date: ________
Exit Slip
Exit Slip: Using the results from the graph below, describe how the peppered moth is evidence of natural
selection over a short period of time? (Refer to the definition of natural selection on the first page of your packet)
Peppered moths are evidence of natural selection over a short period of time because the light-colored moths
increase/decrease (circle one) when … _____________________________________________________________________
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The dark colored moths are evidence of natural selection because their population ___________________
when … __________________________________________________________________________________________________
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