Peppered Moth Simulation
Purpose:
Explain how an organism’s phenotype will affect its survivability within its environment.
Background Information: (summarize the information into 3 sentences)
Natural selection, the reproductive success of organisms best suited to their environment, is a driving
force in evolution. Natural selection occurs within populations, which are interbreeding groups of
individuals of the same species. Genetic variation, the alternative types of genes for inherited traits, is
one factor in the reproductive success of certain members of a population. The result of natural
selection is adaptation, the changing of a population so that it is better suited to its environment.
Industrial melanism is the term used to describe the adaptation of a population by the darkening of
its individuals in response to industrial pollution. One example of rapid industrial melanism occurred in
populations of peppered moths, Biston betularia, in the area of Manchester, England, from 1845 to
1890. Before the Industrial Revolution, the trunks of 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 lightcolored with dark spots. As the Industrial Revolution progressed, the tree trunks became covered
with soot and turned dark. Over a period of 45 years, a dark variety of the peppered moth became
more common.
Hypothesis: (copy down and fill in)
If the color of the prey matches the background, then ____________________________________________
_________________________________________________________________________________________________.
Pre-lab Questions:
A. The table below contains data from a 10-year study of 2 varieties of the same species of
peppered moth. The numbers represent moths captured in each of 10 consecutive years.
The traps were located in the same area each year.
Year
1
2
3
4
5
6
7
8
9
10
Number of Light
Moths Captured
551
537
484
392
246
225
193
147
84
56
Number of Dark
Moths Captured
85
112
198
210
281
357
412
503
594
638
1. Using the data provided in the table construct a graph. Label the axes with the years of the
study x-axis (horizontal axis) and the number of moths captured y-axis (vertical axis). Use
different colored pencils (or a solid line and a dotted line) to indicate each of the 2 color
variations of the moth. Be sure to include a legend at the right top corner of the graph and a
title at the top of your graph.
Peppered Moth Simulation
2. Using the graph you made describe what happened in the population of peppered moths in
the sample area.
3. What is the relationship between the environment and the color of the peppered moth?
4. Explain why an increase in the number of dark-colored peppered moths occurred during the
Industrial Revolution.
5. What effect do you think the modern use of cleaner-burning fuels has on the environment and
the peppered moths near Manchester, England today?
Materials for lab activity:
-Sheet of white paper
-Sheet of newspaper
-forceps
-white paper disks (60)
-newspaper disks (60)
-timer
Procedure:
1. Work with a partner, and decide which of you will be the “predator” and which will be the
timekeeper.
2. Place a sheet of white paper on your lab table. If you are the timekeeper, scatter 30 whitepaper disks and 30 newspaper disks on the white paper while your partner looks away. The
disks represent a bird’s prey. If you are the predator, use forceps to pick up as many disks as
possible in 30 seconds while your lab partner watches the time. The forceps simulate a bird’s
beak.
3. Count the number of each type of disk picked up in 30 seconds. Record these numbers in
data table I below.
4. Replace the white paper with a sheet of newspaper. If you are the timekeeper, scatter 30
white paper disks and 30 newspaper disks on the newspaper. If you are the predator, repeat
the hunting procedure while your partner watches the time. Again record the numbers in the
data table.
5. Change roles, and repeat steps 2-4.
6. Use data table 2 to calculate the percent of available prey recovered for each trial.
Data Table 1
Trial
Back-ground
1
2
3
4
White paper
Newspaper
White paper
Newspaper
Newspaper
disks
scattered
White disks
scattered
Disks picked
up contrasting
background
Disks picked up
matching
background
Data Table 2
Trial
1
2
3
4
% of available prey eaten
contrasting
% of available prey eaten matching
Peppered Moth Simulation
Analysis:
1. What do the two different backgrounds represent?
2. What did he experiment show about how prey are selected by predators? Did your
experiment support your hypothesis?
3. If the cutouts represented moths, what moth coloration is best adapted for a dark
(newspaper) background? How do you know? What data from your experiment can you use
to support your answer?
4. Are the light and dark colored moths different species? How can you tell? (think about the
definition of a species)
5. How might the gene for dark coloration in the peppered moth have originated?
6. How does the percent of prey-recovered compare between the two different backgrounds?
7. How does the data you collected in the experiment compare to the data from the 10-year
study?
Conclusion:
Write a 5 sentence summary that includes the following items; a) what the experiment tested
and showed, b) how the experiment relates to natural selection, and c) how the experiment
is an example of evolution.