Name: dylan beattie Date:

Student Exploration:Natural Selection

Directions: Follow the instructions to go through the simulation. Respond to the questions and
prompts in the orange boxes.

Vocabulary: biological evolution, camouflage, Industrial Revolution, lichen, morph, natural selection, peppered
moth

Prior Knowledge Questions (Do these BEFORE using the Gizmo.)

The peppered moth (Biston betularia) is a common moth found in

Europe, Asia, and North America. It is commonly found in two forms, or
morphs: a dark morph and a light, speckled morph. Birds are a frequent
predator of the peppered moth.
1. Which morph do you think would be easier to see on a dark tree
trunk? the light morph

2. Which morph do you think would be easier to see on a light tree

trunk? the dark morph

Gizmo Warm-up
The Natural Selection Gizmo allows you to play the role of a bird feeding on
peppered moths. The initial population of 40 moths is scattered over 20 tree
trunks. Click on moths to capture them. Click the Next tree button (or the
spacebar on your keyboard) to advance to the next tree.

1. Check that LIGHT TREES is selected. Click Play ( ), and hunt moths
for one year.

A. How many dark moths did you capture? 3

B. How many light moths did you capture? 3

C. Camouflage is coloring or patterns that help an organism to blend

in with the background. Which
type of moth is better camouflaged on light bark? the light moths

2. If a forest contained mostly light-colored trees, which type of moth would you expect to be most common?

light colored moths

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 Get the Gizmo ready:
Activity A:
● Click Reset ( ).
Light trees
● Check that the LIGHT TREES tab is selected.

Introduction: Before the 19th century in England, the air was very clean. The bark on trees was usually light in
color. Abundant lichens growing on tree trunks also lightened their appearance.

Question: How does the color of a peppered moth affect survival?

1. Predict: Over time, what will to happen to the populations of light and dark moths on light trees?

there will be more light moths than dark moths because the dark moths get caught more.
as the dark moths get caught more they are unable to reproduce as much, which means
there are less and less dark moths.

2. Experiment: Click Play and hunt peppered moths on light tree trunks for five years. In each year, try to
capture as many moths as you can. Note: You can use the spacebar on your keyboard to quickly advance
to the next tree.

After 5 years, select the TABLE tab and record the percentages of each moth type. (Note: The table
shows current populations of each moth, not the number of captured moths.)

Year Dark moths Light moths

0 ? ?
1 5 3
2 4 2
3 1 6
4 9 9
5 8 5

3. Analyze: What do your results show?

It shows that for most of these examples the dark moths got caught more than the light
moths.

4. Apply: Which type of moth do you think was more common before the 19th century, when most trees were
light in color?

The light moths.

5. Extend your thinking: What strategies did you use to hunt for moths?

I just looked for any abnormal looking thing on the tree. if it looked abnormal or like a
moth i clicked it .
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 Get the Gizmo ready:
Activity B:
● Click Reset.
Dark trees
● Select the DARK TREES tab.

Introduction: The 19th century was the time of the Industrial Revolution in England. Most of the new
industries used coal for energy, and the air was polluted with black soot. In forests near factories, the soot
coated trees and killed lichens. As a result, tree trunks became darker.

Question: How did air pollution affect moth populations?

1. Predict: Over time, what will to happen to the populations of light and dark moths on dark trees?

The dark moths will increase while the light moths population will lower.

2. Experiment: Click Play and hunt peppered moths on dark tree trunks for five years. In each year, try to
capture as many moths as you can.

When you are done, select the TABLE tab and record the percentages of each moth type.

Year Dark moths Light moths

0 ? ?
1 4 8
2 1 3
3 1 9
4 5 1
5 1 1

3. Analyze: What do your results show?

It showed that the dark moths were caught less than the light moths.

4. Apply: Which type of moth do you think was more common during the 19th century? Why?

The dark moths because they were caught less. When the light moths were caught they
were unable to reproduce which means they died out.

5. Draw conclusions: Natural selection is the process by which favorable traits tend to increase in frequency
over time. How does this experiment illustrate natural selection?

It shows that when the environment is more favorable to certain things, those certain
things grow in population. The things that aren’t favorable (in this case either one of the
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 butterflies) they get caught more and die. When those things die they are unable to
reproduce which means that species can die out.

6. Think and discuss: Did the changes you observed in the moth populations result from individual moths
changing colors? Or did they occur because the best-hidden moths survived and reproduced, passing on
their colors to their offspring? Explain your answer.

They occurred because the best-hidden moths survived and reproduced which meant that
type of moths population grew. For example, in the first part of this assignment where I
looked at light trees. In that part of the assignment the light moths were found less. When
they were found less they were able to reproduce more than the dark ones (who got
caught more).

7. Extend your thinking: Biological evolution is the process by which populations of organisms change over
time. How could natural selection lead to evolution? If possible, discuss your answer with your classmates
and teacher.

Using this assignment as an example, after the 19th century when the trees got darker
the dark moths were thriving while the light moths were not. As this environment got more
“normal” for the moths the light moths would get caught more and more. As the light
moths population got so small the dark moths population got bigger and bigger. Lets say
eventually the light moths went extinct. This would be evolution. Now there are only dark
moths in the world (in this example). I am not quite sure this makes sense but in my mind
it did.

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