Learning from the Fossil Record
Grade 8 Science
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Part C: Conclusions about the Peppered Moth
This simulation is based on a real experiment done by the English scientist, Dr. Kettlewell.
Here is a summary of his research:
Period 1: Before the Industrial Revolution the birch trees around Manchester, England had a light
(almost white) bark.
Period 2: During the Industrial Revolution, the smoke from factories added a layer of dark soot to the
surface of the birch trees. This process took about 100 years, during which time the trees gradually
changed from white to gray to dark black.
Period 3: Currently, with strict pollution laws, the soot is disintegrating and the trees are gradually
returning to their original white color.
Other Facts: Throughout all of this time, the peppered moth has been the dominant prey of several
bird species. The peppered moth is active at night, and during the day, when the birds hunt, they
sleep on the surface of these birch trees.
Base on this information, answer the following questions.
1.
During each period described above, which moth color would be eaten by the birds more
frequently? Why?
Period 1 – The dark moths, because they would not blend in with the trees at all, and would be
the first moths to be spotted easily
Period 2 – The lighter moths, because they would contrast more against the darkening trees,
and would be the first ones to be seen.
Period 3 – The darker moths again, because they no longer blend in with the trees as they
lighten, so they would now be spotted again.
2. If the uneaten moths, during each period, mated what color offspring would tend to become
more common? Use a Punnett Square to help you with this. Note: Darker is the dominant
phenotype over lighter.
Period 1 – The lighter moths will tend to be more common, because you will need two
homozygous recessive parents to create the light moths, and if the darker moths are being
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Learning from the Fossil Record
Grade 8 Science
Name:
Date:
eaten, the ddxdd combination will gradually become more common as the dominant trait,
darker bodies, gets killed off.
Period 2 – The darker moths will be more common now, because the lighter ones will be getting
eaten instead of the dark ones. They will have more time to reproduce, so they will have more
children than the lighter ones, so there will be more darker children.
Period 3 –Soon, the gene pool will be reduced to only white moths because the black moths will
be getting eaten at this point. The white moths will now have as much time as they did in the
first period to reproduce.
3. Dr. Kettlewell concluded that the color of the moth evolved (changed) over time due to changes
in the environment. Explain what he meant by this.
Originally, the moths were essentially “made” to survive in that environment as that white with
black spots color, and now that their environment has changed, so they needed to change to
survive.
4.
Charles Darwin, Father of Evolution, referred to these changes as “survival of the fittest”. What
did he mean by this?
The animals that are the “fittest” to survive ended up surviving, because they are the most able
to survive. They have an advantage over their counterparts in their environments because they
could survive better.
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Learning from the Fossil Record
Grade 8 Science
Name:
Date:
WEBSITE DESCRIPTION STUFF THINGS:
1. Peppered Moths are a typical species of Moth that can be found throughout Europe, Great Britain,
and North America. They are white with black spots and hide by sleeping on the barks of trees that have
bark and fungus patterns that are very similar to their own bodies. Their cocoons and larvae are also
suited for hiding, and are shaped like pieces of branches so that they cannot be seen against branches
they may be resting on.
2. In the mid-1800’s, a researcher noticed that he found a completely black peppered moth. Over the
next few years of the Industrial Revolution, the number of dark moths began to rise in a synchronous
correlation with the tree barks they hide against. Scientists realized that this was because of Charles
Darwin’s suggested theory of natural selection, and the connection was made.
3. Dr. Kettlewell figured out that the reason the black moths survived on the darker tree trunks was
because they had a survival advantage. A moth with a color like the bark it rests on was twice as likely to
survive over a moth that didn’t match its background. They had adapted to be more likely to survive
because of natural selection.
4. During the simulation of the light forest, I changed the population to 57 percent light, 43 dark. During
the simulation of the dark forest, I changed the population to 39 percent light moths and 61 percent
dark moths. This proves that the moths that could blend in had a better chance of surviving.
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Learning from the Fossil Record
Grade 8 Science
Name:
Date:
Part D: Key Concepts – A Summary
1. WAL how the environment impacts the inheritance and traits of living things.
2. WAL to use models to explain scientific phenomena.
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