Points for this lab will be based on:

1. A pre-lab quiz taken on Blackboard worth 20 points.
2. A lab activity worth 60 points.
3. A post-lab quiz worth 20 points.

---

Exercise 1: Variation

We will test one prediction dealing with the process of natural selection:

Prediction: If the theory of natural selection is true, one should find observable variation in a sample population of organisms.

Humans can easily see variation in people around them but often think of members of other species of animals or plants as being essentially identical. A squirrel running across the street looks to most of us like any other squirrel we have seen before. This exercise is designed to let you analyze a population to determine if variation exists. As a group you will examine a "populations" of organisms provided. Each population consists of between 50 and 100 individuals. Each population consists of only a single species. Working as a group, you are to examine the individuals and sort them by size variation. You can sort them by using a ruler or guide for assessing size available at your lab table and arranging the individuals of your population out on your tables. On one answer sheet for your group, graph the frequency of individuals in each of your identified classes. What pattern of variation does your graph show for the population? Record on the answer sheet the two extremes in the range of variation you are able to identify. As a group, discuss why one class of variation is most common, or if another pattern emerges, explain possible reasons for this. Also on the answer sheet record one type of variation you can identify, other than that you graphed. It is sometimes surprising how variable individuals of a population are. This variation is essential for natural selection to operate.

Exercise 2: Artificial Selection

Darwin provided a simple but powerful analogy to natural selection in his first description of the process. He noted that people have been changing the form of domestic animals and crop plants for thousands of years by the process of selection. The process simply requires a person to select individuals to breed that are most like what the person wants. In each generation one or a few individuals will often have some features that lean toward the desired form. All domestic dog breeds have been the result of such selective breeding. Examine the samples of dog breeds available in the lab. As a group, discuss the variation you see within a sample and provide two examples of variation shown in the sample. Write these on your answer sheet. How were these varieties produced?

Exercise 3: Video

You may wish to take notes which can be used while taking the quiz afterwards.

---

Make sure that you take the pre-lab quiz on blackboard before you come to class.

---

Click here to go back to page 1.