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Leah Crenshaw
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Peppered Moth Simulation
Objective: Using paper cutouts of moths from black paper and newspaper, we will
simulate the affect of pollution on the environment of the peppered moth of Manchester,
England.
Hypothesis: When the background is newspaper, the moth cutouts that are black will be
more targeted by “predators.” When the background is black paper, the moth cutouts that
are newspaper will be more targeted by predators.
Materials:

Stopwatch

30 Moth Cutouts (Newspaper)

30 Moth Cutouts (Black Paper)

Large Sheet of Newspaper

Large Sheet of Black Paper
Procedure:
1. Lay out a sheet of newspaper. This represents an unpolluted tree.
2. Lay out all 60 paper cutouts on the newspaper.
3. Have on group member start a stopwatch.
4. Have another group member use their non-dominant hand to pick up as
many moth cutouts as possible (regardless of color) using only the thumb
and first (pointer) finger. Raise hand over head before setting down each
individual moth.
5. Continue number 4 for thirty seconds.
6. Record the number of newspaper moths and black moths that are left on
the paper. These are the “survivors”
7. Leave all of the moths that were removed off the paper and mentally
double the number of survivors. This is the number of the 2nd generation.
Record this number.
8. Repeat steps 3 through 5.
9. Record the number of “survivors” again. Make sure the number is double.
Then, double the number of survivors again. This is the third generation.
10. Repeat steps 1 through 9 using the black paper instead of newspaper to
represent polluted trees.
Data:
Results for Newspaper Background:
Moth Color
Gen. 1
Survivors
Gen. 2
Survivors
Gen. 3
Light
30
30
60
52
104
Dark
30
22
44
34
68
Results for Black Background
Moth Color
Gen. 1
Survivors
Gen. 2
Survivors
Gen. 3
Light
30
16
32
26
52
Dark
30
30
60
44
88
Results in Bar Graph Format for Newspaper Background:
Note: Grey color represents Newspaper Moth; Black color represents Dark Moths.
Simulated Population of Moths
120
Number of Moths
100
80
60
40
20
0
1
2
3
4
5
Gen 1, Survivors, Gen 2, Survivors, Gen 3
Results in Bar Graph Format for Black Background:
Note: Grey color represents Newspaper Moth; Black color represents Dark Moths.
Simulated Population of Moths
100
90
Number of Moths
80
70
60
50
40
30
20
10
0
1
2
3
4
5
Gen 1, Survivors, Gen 2, Survivors, Gen 3
Discussion Questions:
1. Which colored moths are most fit for an unpolluted environment? Use you results
to support your answer.
The peppered moths were more fit for the unpolluted environment as shown
by the evidence in that 30 Generation 1 peppered moths survived, while
only 22 black moths survived with the newspaper (unpolluted)
background.
2. Which color moths are most fit for a polluted environment? Use you results to
support your answer.
The black moths were more fit for the polluted environment, as shown by the
evidence in that 30 Generation 1 black moths survived, while only 16
Generation 1 peppered moths survived with the black (polluted)
background.
3. What variations existed in the moth population?
The moths were either black or peppered.
4. Was there differential reproductive success in the moth population? Explain.
There was different reproductive success in the two simulations. For example,
with the newspaper background, the peppered moths had more
reproductive success, while with the dark background, the dark moths had
more success.
5. Were successful traits passed on to the next generation?
The more successful moths would pass on the successful traits to their
offspring, such as with the newspaper background, the peppered body
gene was passed on and likewise with the black moths and black
background.
6. Did the population change over several generations?
The population became more weighted in the successful moth's favor over
several generations. With the peppered background, the population was
more heavily peppered. With the dark background, the population was
more heavily dark.
7. What process plays out in this simulation?
This simulation is a good example of Darwin's “Natural Selection”, which
states the best organisms for an environment survive and pass on gene,
while the ones that are not well-suited to the environment will die and not
pass on their genes.
Conclusion:
The hypothesis stated: “When the background is newspaper, the moth cutouts that
are black will be more targeted by predators. When the background is black paper, the
moth cutouts that are newspaper will be more targeted by predators.” This hypothesis was
strongly supported by the data. The first part of the hypothesis, “When the background is
newspaper, the moth cutouts that are black will be more targeted by predators.” was
supported by the data of the first part of the simulation with the newspaper background in
which the peppered moths had a much higher survival rate than the black moths. The
second part of the hypothesis, “When the background is black paper, the moth cutouts
that are newspaper will be more targeted by predators.” was supported by the second part
of the simulation in which the black moths had a much higher survival rate than the
peppered moths.
There were some questionable parts of the simulation, however. As always,
human error is a part of any experiment. This can be remedied will multiple trials with
different test groups. There was also the minor problem of using a black tabletop instead
of the same black paper the moths were cut out of. This caused a distinct difference in the
shades of black and slightly skewed the results of the black background simulation. More
trials would be necessary with shades of black that matched more closely.
This experiment was a good example of Natural Selection. Natural Selection is a
key mechanism to evolution. It is the idea that when an organism in a species has a trait
that makes it more likely to survive in its environment, it will be more likely to have
offspring than an organism of the same species without the trait. This applies well to the
peppered moth population of Manchester, England in the mid-1800's. The moths had
evolved to have salt and pepper coloration that was nearly inscrutable from the lichen on
the bark of the trees the rested on. However, with the Industrial Revolution, pollution
caused the lichens on the trees to die off and the trunks of the trees were strained black
with soot. The peppered moths were no longer able to blend in with their new
environment and, as shown by the simulation, and they died off due to predation. The
peppered moth population was gradually replaced with darker moths that could blend in
on the blackened trees. This is a perfect example of Natural Selection.