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Natural Selection Worksheet 1

Over time following the Clean Air Act of 1959 in England, the population of peppered moths shifted from mostly light-colored moths to mostly dark-colored moths. This was due to natural selection, as the dark moths had better camouflage against the darkened tree trunks and were less likely to be preyed upon by birds. If there were no birds eating the moths, both color morphs would likely continue to exist at stable frequencies. Given that air quality has been maintained since 1995, the frequency of dark moths would be expected to remain high or increase further over the coming decades and centuries due to continued natural selection.

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2K views3 pages

Natural Selection Worksheet 1

Over time following the Clean Air Act of 1959 in England, the population of peppered moths shifted from mostly light-colored moths to mostly dark-colored moths. This was due to natural selection, as the dark moths had better camouflage against the darkened tree trunks and were less likely to be preyed upon by birds. If there were no birds eating the moths, both color morphs would likely continue to exist at stable frequencies. Given that air quality has been maintained since 1995, the frequency of dark moths would be expected to remain high or increase further over the coming decades and centuries due to continued natural selection.

Uploaded by

api-259727482
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as PDF, TXT or read online on Scribd
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Name_________________________________________

Evolution Natural Selection

Date______
Exercise 1

1) In England, the trunks of trees were blackened for many years by soot from factories. After
passage of the Clean Air Act in 1959, the trunks became lighter. Scientists in England studied
the peppered moth (Biston betularia) which rests on these trees and is preyed upon by birds.
They noticed the following change in frequencies over a period of time.
Environmental
Factor

Environmental
Factor

Whiter Tree
Trunks/Birds

Whiter Tree
Trunks/Birds

1959

Light colored moth

1979

1995

Dark colored moth

Describe what is happening to the moth population over time in the boxes above.

How does this show natural selection happening over time?

How would the scenario have changed if there were no birds to eat the moths?

England has continued to maintain the quality of air that it had in 1995, what distribution of moths
would you expect to see now, in 25 more years, in 75 more years? Justify your answer.

Unit 2 Change Over Time

While realistically impossible, suppose there was no change in the environmental conditions for a
population of organisms for thousands of years, what would you expect to happen to Evolution by
Natural Selection? Justify your answer by citing evidence from the lab, or the text, or this worksheet.

In the story The Elephants Child, Rudyard Kipling suggests that elephants have long trunks today
because one curious elephant (Loxodonta africana) had his nose stretched by a crocodile
(Crocodylus niloticus). The elephant then found that his stretched trunk allowed him to get food more
readily than his short-nosed relatives. Suppose that a curious elephant did get his trunk stretched by
a crocodile. Finish the storyboard shown below. The frequency of the trait after the curious elephant
got his trunk stretched is shown. You need to show the frequency of the long trunk in his childrens
generation, and finally, 50 generations after the stretching.
Finish the boxes below:
Environmental
Factor

Curious Elephants Generation

Key: Short Trunk:

Environmental
Factor

His Childrens Generation

50 Generations Later

Long Trunk:

Describe what is happening in the boxes above.

Why would the scenario in the story not really happen in life?

Unit 2 Change Over Time

Unit 2 Change Over Time

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