In this lab you will simulate natural selection. During the exercise you will represent a predatory bird that feeds on woolly worms. The woolly worms are pieces of colored yarn which have been randomly distributed over an area on the school grounds. Some of the wool pieces will blend into the habitat while others will be easy to spot. The colored yarn woolly worms that you "eat" will be tallied and recorded, and students will determine if the wool colors were collected randomly or by a selection process.

Purpose: Simulate a predator-prey relationship to better understand the process of natural selection.

Hypothesis: Look at a picture of the environment and make a prediction about how coloration will affect which worms will be eaten and which worms will survive.

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Null hypothesis: Remember that we cannot prove hypotheses in science – we can only support hypotheses with repeated experiments. However, we can disprove hypotheses with data.

So professional researchers create a null hypothesis that predicts no significant change in the data. This is typically the opposite of what researchers want to show – scientists try to obtain data that does show a significant change. If they do, then they reject their null hypothesis, and therefore indirectly support their true hypothesis.

Example: Medical researchers are trying to show that the new drug X works

better than aspirin at curing headaches.

Hypothesis: New drug X works better than aspirin.

Null hypothesis: New drug X works just as well as aspirin.

Data:

Conclusion: Bar graph clearly shows drug X working better than aspirin. Null hypothesis is rejected, and therefore original hypothesis is supported (though not proven).

If you predicted a change in the worm population in your hypothesis above, write a null hypothesis that you can try to disprove with this experiment.

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Procedure:

1) Worms will already have been randomly spread out in the environment.

2) In a 45 second period, predators walk around and pick up as many worms as they can find. React like a predator – when you sight a worm, focus in on it and pick that worm up.

3) At the end of the time period, groups come back and count the number of worms picked up by color. The recorder of the group will note the group results.

4) After recording, the predators go back and randomly spread the worms for the next group.

5) After each group has completed their trial, return to the classroom to record group and class data and calculate the survival percentage for each color.

Title: ______

Results from actual lab / Expected results for null hypothesis
Color / A.
Total worms / B.
Eaten worms / C. Surviving worms
(A# - B#) / D.
Survival % from lab
(C# / A# x 100) / E.
Surviving worms if no selection
(C9 / 8) / F.
Survival % if no selection
(E# / A# x 100)
1.
2.
3.
4.
5.
6.
7.
8.
9. Total

Woolly worm lab report

Please include the following in your lab report:

1) Title – must contain IV and DV in the title (not “woolly worm lab”)

2) Restate the purpose and your hypothesis. Also state the null hypothesis that you are trying to disprove in order to better support your hypothesis.

3) Background information – In a paragraph, explain Darwin’s theory of natural selection and how a population changes over time to better adapt to its environment. Remember that our discussion included 4 components to Darwin’s argument.

4) Include a brief summary of the procedure from the lab. What are we simulating in the activity?

5) Include your data (you can include the data table given on page two). Also create a fully labeled graph of the key data from the table (graph the data from both columns D and F from the data table so you can compare the experimental results with the predicted results for the null hypothesis).

6) Address the following questions in a conclusion paragraph (or paragraphs).

a) Restate the purpose of this lab.

b) State your major findings. Analyze your graph, including a discussion of the following:

  • Did the actual lab results match the results predicted by the null hypothesis or not?
  • Make a prediction about the coloration of the population 100 generations into the future.

c) Were you able to disprove the null hypothesis? Also indicate whether or not your data supported or did not support your hypothesis.

d) State an improvement to this simulation lab. One possibility might be to suggest a way to more closely represent natural processes in this simulation.

e) For the lab extension, describe another environment where a different color worm might survive better. How you could test to see whether your idea is correct?