Introduce the activity by explaining that the school newspaper has decided to include a special section on evolution and medicine. The editor of the newspaper has asked for help. Students will use what they have learned about evolution and medicine to review an article written by a fictional fellow student. The task is to serve as a peer reviewer who identifies incorrect or misleading statements, corrects them, and explains why the corrections are necessary.

In this activity, students should use what they have learned throughout this supplement to review a short article and write a short summary. This task is not a research project—students should be able to analyze the information provided and apply it to a new situation.

Give each student one copy of Master 5.1, Editing an Article about Vitamin C and Evolution. Briefly review the instructions with the class before asking students to work in groups of four. Explain that all group members should read the first paragraph together. Then two group members should review and comment on Paragraph 2, and the other two should review and comment on Paragraph 3.

Students should concentrate on the author’s explanations of the data rather than the accuracy of the data. For the purpose of this activity, the scientific facts are accurate. For example, L-gulonolactone oxidase (GULO) is one of the enzymes required for vitamin C biosynthesis. Vitamin C is not synthesized in humans, other primates, guinea pigs, and some bats, and the gene sequences and the evolutionary tree are scientifically accurate. The text contains some incorrect explanations of the data, based on common misconceptions. (For example, the information in the tree may be interpreted incorrectly.)

One strategy that students can use for the review is to place a number next to the piece of information they wish to rebut. Then, in their science notebooks, they can explain for each number what is incorrect, why it is incorrect, and how to correct it.

After each pair of students within the group has completed the review, pairs should discuss their comments with the other two group members (who reviewed the other paragraph).

After groups finish, hold a class discussion to check students’ understandings. Ask for volunteers to identify one thing that they felt needed to be corrected and how they changed it. Check whether other class members agree with the volunteers’ ideas. If they disagree, they should be prepared to explain why and how they would (or would not) change a statement. Project Master 5.2, Editing an Article about Vitamin C and Evolution, Answer Key, at the end of the discussion. Point out any misconceptions or misinterpretations that students did not identify.

It will be important to resolve any discrepancies so students do not leave the class confused about an issue or accepting common misconceptions.

Although it’s beyond this supplement’s content, you may wish to discuss the role of evolutionary processes in the loss of the ability of make vitamin C — if your class seems to have a good understanding of the example. If the loss of the ability to make vitamin C were driven by natural selection, then individuals with a mutation that disabled the GULO gene would have an advantage in survival or reproduction. This scenario is unlikely, however. It is more likely that individuals that had mutations in the past that disrupted the GULO gene were not at a disadvantage for survival or reproduction, and the loss of the ability to make vitamin C was due to chance.

Instruct students to take a few minutes to create an illustration that explains the process of evolution with an example from one of the earlier lessons. Have students count off by fours.

There are four examples from the earlier lessons, so this approach ensures that approximately equal numbers of students will illustrate each example.

1. Selection for methicillin-resistance in Staphylococcus aureus (MRSA)
2. Selection for lactase persistence in some human populations
3. Selection for alleles associated with alpha-thalassemia in some human populations
4. Selection among influenza viruses

Outline on the board the elements of the task:

• Students should create one or more simple illustrations that describe how the process of natural selection works.
• Before making the illustrations, students should review the work in their notebooks from the previous lessons to help them reflect on natural selection and the major principles involved in the process.
• Students should use the example they were assigned in Step 7 as the focus of the illustrations.
• The illustrations should include labels and enough explanatory text that a reader unfamiliar with natural selection can understand how the trait of interest changed in a population over time.

Collect students’ illustrations when they are complete. Ask for volunteers to explain the features of the illustrations. For each example, guide the discussion to bring out the five major principles of natural selection.