World Population and Beak Size

Topics: World population, Population ecology, Population Pages: 6 (1548 words) Published: February 12, 2014
Before you undertake this assignment, please read carefully the handout that gives an overview of EvolutionLab. This will make it much easier for you to understand the assignment and complete it correctly. 1. There are many ecological and biological factors that affect evolution. In EvolutionLab, two populations of finches are tracked over the course of 300 years on two different islands to see how changing the traits of the birds and their environment affect their long term viability as a sustainable population. Let’s begin by doing a “null experiment” where conditions are identical on the two islands. Set the “revisit in” drop-down menu to 300 years and then click the Run Experiment button. Click the Input Summary tab and note that in this experiment and note that all factors (both biological and ecological) were identical. Then click the Beak Size tab. Which of the following is true? (Keep in mind that the term “rate” refers to how fast, not how much. Also, we are looking for major differences, not minor ones due to random chance.) a. When all factors are equal, the beak size of both species increased at a different rate over 300 years. b. When all factors are equal, the beak size of both species increased at roughly the same rate over 300 years.

2. Click the Population tab. Which of the following is true?

a. The finch populations of both islands increased at roughly the same rate over 300 years. b. The finch populations of both islands increased at different rates over 300 years

3. Based on the results for beak size and population numbers, what can you conclude about evolution when all factors are equal?

a. While the populations both increased in size, mean beak size did not. Therefore, when all factors are equal, evolution does not occur. b. The mean beak size of both populations increased. Therefore, under these circumstances, evolution did occur in both species. c. Neither (a) nor (b).

4. Click the New Expt button and then click the Change Inputs button. Increase the initial beak size of the Darwin Island finches to 30 mm and decrease the initial beak size of the Wallace Island finches to 10 mm. Click on the Precipitation button and look at the distribution of hard, medium, and soft seeds. Note that most of the seeds are hard. Click the Done button and then click the Run Experiment button. Which statements below are true?

a. Beak size of Darwin Island finches varied considerably over time. b. Beak size of Darwin Island finches showed little variation over time. c. Beak size of Wallace Island finches showed little variation over time. d. Beak size of Wallace Island finches varied considerably over time. e. Both (a) and (c).

f. Both (b) and (d).

5. After clicking the Beak Size tab, indicate which of the below statements most accurately describes what occurred? (Note: birds with bigger beaks are better able to utilize hard seeds and therefore have higher survival rates.)

a. On Wallace Island, individuals with large beaks were better able to utilize the more abundant hard seeds and survive a higher rates. This resulted in an evolutionary increase in mean beak size on Wallace Island over time. b. On Darwin Island, most of the finches already had large beaks and were adapted to the more abundant hard seeds. This is the reason why mean beak size remained relatively constant over time c. Both (a) and (b).

d. None of the above.

6. After clicking the Population tab, which of the below statements most accurately describes what occurred? (Note: birds with bigger beaks are better able to utilize hard seeds and higher survival rates.)

a. As mean beak size increased on Wallace Island, individuals with large beaks were better able to utilize the more abundant hard seeds and survived at higher rates. This resulted in a slow increase in population numbers over time. b. Because mean beak size of finches on Darwin Island were large, the birds were well-adapted to the abundance of hard seeds. Therefore...
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