Name
Modeling Camouflage
and Natural Selection
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As part of his theory of evolution by natural selection, Charles Darwin
proposed that organisms best adapted to their environment survive
ind reproduce more successfullythan other organisms. Camouflage,
the concealment of an organism because of its color, is an example of
an adaptation that can increase an organism's chance of surviving to
reproduce. Organisms that are more difficult for predators to seeare
less likely to be attacked. In this investigation, you will examine the
effect of camouflage on the survival of a prey species.
PepperedMoth SurveY
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Industrial melanism is the term used to describe
the adaptation of darkening by 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 1845to 1890.
Before the Industrial Revolution, the trees in the
forest around Manchester were Iight grayish-green
due to the presence of lichens on their trunks'
Peppered moths, which lived in the area, were
Iighi-colored with dark spots.Their coloring served
ai camouflage against predators, especially birds'
As the Industrial Revolution progressed, the trees
became covered with soot, which turned the trunks
dark. Over a period of 45 years, a change took place
in the peppered moth population in this area.
In this investigation, you will simulate a predatorprey
^hur situation and determine if color contrast
un effect on the ability of a predator to rapidly locate prey. In the second part of the investigation, you will study the data on peppered moth
coloiation as actually reported over the course of several years. You will
then determine the relationship between the environmental changes and
the color variations of the peppered moths by using the research data to
graph the results of an environmental adaptation.
. graph paper
. paper disks, Punched out of
netspuP"t with a hole Punch (60)
. sheet of newsPaPer
. pencils, each with a
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PartA
Simulating Predator-Frey
Relationships
1. You will use the discs of white paper and newspaper to simulate prey.
The paper discs will be placed on backgrounds that either match or
contrast with them. You will use forceps to simulate a bird's beak and
capture as many of your prey as possiblein 15 seconds.
Place a piece of white paper on your lab desk. While your teammate
is looking away, scatter 30 white disks and 30 newspaper disks on the
papet'.When your partner is ready with the forceps, let the hunt begin
and start timing.
2. When 15 seconds have elapsed, count how many of each type of disk
were picked up. Compare the number of captured disks of each type
to the number that remained on the paper. Record the numbers in the
data table in the Additional Records and Observations section
3. Replace the white paper with a sheet of newspaper.While your partner is looking away, scatter 30 newspaper disks and 30 white disks.
Repeat the hunting procedure with your partner and record the
number of disks picked up on the Additional Records and observations
sectiorL
Also record the numbers of each type remaining
4. Change roles. You play the role of predator, while your partner sets
up the disks. Repeat Steps 1-3 above.
Did you andysyy partner each pick up the sanle amount of "prey"?
5. After you have recorded data for one trial using a white background
and one trial using a newspaper background for each lab partner,
comlrute the Percentage of Available Prey Recovered for the contrasting and matching background situations.
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do this, divide the total number of discs recovered that
contrttsted with their background by the total number of discs of
that type. Repeat this procedure with the total number of discs
recovered that motched their background.
For example if you scatter 30 newspaper discs and 30 white discs
on a sheet of newspaper, and you recover 5 newspaper (matching)
discs and 15 white paper (contrasting) discs,your recovery rate is
',rox iOOTo= 17o/oforthe matching backgrouhd situation.
Likewise, your recovery rate is
* x 100% = 50o/ofor the contrasting background situation.
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Record your computed percentages in the table in the Additional
form. Comparing perRecords and Observations section of your
centages rather- than raw numbers will give you a clearer picture of
the effect or lack of effect that background contrast has on predation.
Background Gontrast and Predation Success
I rral
Newspaper
Part B
White
Percentage
Total number of
disks plcked up
Total number of
disks scattered
Backgrouod
Number
available
of
prey recovered
Contrasting
Matching
Contrasting
Matching
baakground
background
background
background
Graphing and Analyzing
Predator-Prey
Relationships
6. Table A represents data Table A
from a l0-year study of
two varieties of the same
speciesof pepperedmoths.
The numbers represent
moths captured in traps
for L0 consecutiveyears.
The traps were located in
the samearea eachyear.
1
Year
Using the data provided in
TableA, constructa graph
l{umber
of light
MothsCaptured
llumber
of 0a*
MothsCapturcd
112
2
3
537
484
4
392
198
210
5
6
7
246
281
225
357
412
8
10
193
147
503
84
594
56
638
comparingthe numbers of each variety of peppered moth. Label the axes with the years of the study (plotted horizontally) and the number of moths captured (plotted vertically). Use
different coloredpencilsor a solid line and a dashedline to indicate
the two color variations.Be sure to includea key beneaththe graph.
8. Use your graph and the textbook,if needed,to answerthe following
questions.
Whatpreys on the p epperedmoth?
lf the bark of trees is dark and the moths thot rest there are lishtcolored, what wlllhappen to the moths?
What ts a mutation?
What could hav e caus ed the ftr st dark- color ed moth to occur ?
What caused the tree trunks of many trees in England to turn from a
light color to a dark color?
Which variety of moth increased over the 7}-year period?
What is the name of this type of evolutionary change?
1. Assume that you are selecting from a field of an equal number of
light and dark "prey." You would expect to pick up an approximately
equal number of each type, if coloration is not important to predation
success.What did your experiment indicate?
2. Using the dataon the graph, draw a conclusionconcerningthe population of pepperedmothsin the sampledarea of England.
3. Explain the reasonfor the increase in the number of dark-colored
moths.
4. What means could be used to return the environment of the peppered
moth to its original state?
5. What effect would cleaning up the environment have on these moths?
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