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Evolution lab

Name ............................................................ Date ...................... Simulating natural selection lab

 

Background:

Prior to the industrial revolution in England, light colored peppered moths were camouflaged on the back of light colored trees. Darker moths were fewer in number due to that they stood out to their predators more. In the mid-nineteenth century, trees that had been light colored became covered with soot. Simultaneously, the number of light colored moths decreased and dark colored ones increased. How did this change occur? In this investigation, you will simulate a similar scenario with “beetle” beans. You will investigate what happens to harmful traits in a population over time.

 

Materials:

1 small “cave” brown bag

hundreds of “environment” (kidney) beans

50+ each of two types of “beetle” beans (i.e. cannellini and black)

Watch or clock

 

Procedure:

      1. Dump all of your environment beans into your cave bag

      2. Examine the difference between your “beetle” beans.

      3. Count out and then add 50 of each of your “beetle” beans

      4. Have one partner time you while you reach into your “cave” bag and pull out beans.

      5. You may only pull one bean out at a time.

      6. If you pull out three environment beans you die! And your partner takes over your turn until the trial is up

      7. Your trial will be two minutes!

      8. After the trial, record the number of each “beetle” bean removed.

      9. Fill in the chart on the bottom of this lab.

      10. Following the directions there, calculate the frequency of each type of “beetle” in the next generation.

      11. Add enough “beetles” to begin the next generation / trial with 100 “beetle” beans

      12. Repeat four more times.

 

Observations:

.............................................................1..................... 2................. 3.................. 4................ 5

A Total # of “beetle” beans................100 ...................100 .............100 ..............100 .............100

B Total # of beans at the start of the generation...........50.............................................................

C Total # of beans at the start of the generation...........50.............................................................

D # of type 1 beans removed during the trial.................................................................................

E # of type 2 beans removed during the trial.................................................................................

F # of type 1 bean remaining in the bag [B-D]................................................................................

G # of type 2 bean remaining in the bag [C-E]...............................................................................

H Total # of “beetle” beans remaining in the bag [F+G].................................................................

I Frequency of type 1 beans in the population [F/H]......................................................................

J Frequency of type 2 beans in the population [G/H].....................................................................

K # of type 1 beans beginning next generation [Ix100]..................................................................

L # of type 2 beans beginning next generation [Jx100]..................................................................

M # of type 1 beans to add back into the bag [new line B].............................................................

N # of type 2 beans to add back into the bag [new line C].............................................................


 

      1. What are the two types of “beetle” beans in your cave?

      2. What are the differences between the two types of “beetle” in your cave?

      3. What is the ratio of “beetle” beans at the start?

      4. What is the ratio of “beetle” beans at the end?

      5. What happened to the relative frequencies of the two types of “beetles” over several generations?


 

      1. Based on your data, was one type of “beetle” bean removed more frequently?

      2. If so, which one?

      3. Why was one type chosen more frequently than the other?

      4. Based on your results, which “beetle” bean traits were harmful to the “beetle” bean population?

      5. Which traits were harmful to the “beetle” beans?

      6. How do you know which traits were harmful?


 

      1. Explain why the frequency of the traits change over the generations.

      1. In our simulation, what is providing the evolutionary pressure?

      2. In our simulation, what is evolving?

      3. If we were to keep running many trials of this, what do you predict would happen to the frequency of the harmful trait?

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