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Name _______________________
Peppered Moth survey
Introduction:
Industrial melanism is a term used to describe the adaptation of an
organism in response to industrial pollution. One example of rapid industrial
melanism occurred in the peppered moth, Biston betularia, in the area of
Manchester, England from 1845 to 1890.
Before the Industrial Revolution, the trees in the forest around Manchester
were light grayish color due to the presence of lichens on their trunks. Peppered
moths, which lived in the area, were mainly light with dark spots, however,
variations in their phenotypes existed. When mutations in the DNA occurred,
moths would be darker in color. However, the color of the lighter moths served
as camouflage against feathered predators. The darker moths were not often
able to reproduce because they did not blend into their habitat. As the industrial
revolution progressed, the trees became covered with sulfur dioxide, turning the
tree trunks dark. Over a period of 45 years, the population of peppered moths
changed from the lighter color, to the predominantly dark species with only a few
light colored individuals remaining. Darwin would call this occurrence natural
selection, because over time the phenotype of the organism changed due to
changes in nature
In this investigation, you will observe the effects of natural selection on the
peppered moth population over the course of several years.
Materials
Graph paper
pencils, colored (2)
Procedure
1. Table A represents data from a 10 year study of two varieties of the same
species of peppered moth. The numbers represent moths captured in
traps for 10 consecutive years. The traps were located in the same area
each year.
Table A
Year
1
2
3
4
5
6
7
8
9
10
Numbers of light moths
captured
556
537
484
392
246
225
193
147
84
56
Numbers of dark moths
captured
64
112
198
210
281
357
412
503
594
638
2. Using the data provided, construct a line graph comparing the numbers of
each variety of peppered moths. Label the x-axis with the “Year of
Capture” and label the y-axis with the “number of moths captured”. Title
your graph. Use a different colored pencil for light and dark moths.
3. Answer the following questions on the back of your graph:
A. What preys on the peppered moth?
B. If the bark of the trees is dark and the moths that rest there are light
what will happen to the moths?
C. What is a mutation?
D. What could have caused the first moth to change from a light variety to
a dark variety?
E. What event caused the tree trunks of many trees in England to turn
from light to dark?
F. Which variety of moth increased over the 10-year period?
G. What is the name of this type of evolutionary change?
Analysis and conclusion: Answer on the back of your graph
1. Using the data on the graph, draw a conclusion concerning the population
of peppered moths in the sampled area of England.
2. Explain the reason for the increase in the number of dark-colored moths.
3. What means could be used to return the environment of the peppered
moth to its original state?
4. What effect would cleaning up the environment have on the moths?
The peppered moth
Many biology and life science text books use industrial melanism as an
example of natural selection, displaying an illustration of the peppered moth
undergoing evolution. Unfortunately, many of the textbook photographs of
the moths consist of preserved specimens stuck to tree bark (if your textbook
contains these photos, note that the wings of the moths may be in unnatural
positions.). This “faking” of moth distribution was used to test the likely-hood
of predation based on visibility of prey. However, this has also been set on by
anti-evolutionists as proof that evolution never happened. Industrial
melanism is a genuine phenomena and the case of the peppered moth holds
up well to scientific scrutiny. The population of dark moths did rise and fall in
response to industrial pollution, and this was most striking in regions of the
countryside with high rates of pollution.
http://evolution.berkeley.edu/evosite/footshooting/IVthe_times.shtml
http://www.millerandlevine.com/km/evol/Moths/moths.html
pics from site above