Four Forces of Evolution
The Four Forces of Evolution are frequently confused, both with each other and with the concept of evolution in general.
Group: Your Color Group
Goals:
Apply the concepts of natural selection, genetic drift, mutation, and gene flow
Apply scientific processes to describing, interpreting, and evaluating data on population variation
Help explain the differences between natural selection, genetic drift, gene flow, and evolution generally
Procedure
Reintroduce yourselves, and make sure everyone knows each other's name.
Within your group, compare your height. Divide into roles based on your number, as follows:
Tallest member of group: recorder The recorder will take notes on the group's discussion. If anything needs to be turned in, the recorder will take care of it.
Next tallest member of group: time-keeper The time-keeper makes sure the group stays focused on the activity and completes the steps on time.
Third tallest member of group: presenter The presenter will speak for the group during the whole class discussion.
Shortest member of group: leader The leader makes sure every voice is heard, and helps encourage the group to stay on-task
The recorder should write down each person's full name, making sure it is spelled correctly, on the top of a piece of notebook paper.
Read through the following scenario: You are a member of the Lovegood-Scamander Expeditionary Force, charged with tracking down the elusive Crumple Horned Snorkack ( Snorkackus crumpcornius). After an arduous trek to a nearly inaccessible mountain valley in Sweden, you found the only known populations of this elusive animal, living on a series of isolated islands in the middle of a cold, deep lake. Pictures of the islands and the typical animals from each will be shown on the screen. (You can also see them here)
As a group, take five minutes to describe the variation (differences) that you see in the different populations of snorkacks. You should describe only, meaning "just the facts", without your interpretations or explanations. What can actually be seen or measured about these populations? The recorder should write down the variation your group describes.
As a group, spend ten minutes creating at two hypotheses to account for the variation you described. Each hypothesis should use the concept of natural selection, gene flow, or genetic drift, and please do not repeat. (For example, you could have one hypothesis that explains the variation entirely through natural selection and one hypothesis that explains it through genetic drift. Or, these could be combined in various ways. Just make sure you use at least two of the three concepts.) The recorder should write down your hypotheses.
As a group, take ten minutes to discuss what data you would need to test your hypotheses. Think widely and creatively. Do you need to take genetic samples from the populations? Do you need to learn more about the environment on each island? Make sure you know how the data would help support or refute your hypothesis.
The presenters will share your hypotheses with the whole class.
As a class, we will discuss what data is needed to test the hypotheses, and why.
Take-home Messages
Genetic drift, gene flow, and natural selection are all different ways in which evolution can take place. (Evolution is not the same as Natural Selection!)
More than one hypothesis can be proposed to explain the same data.
The process of science involves describing data, creatively considering hypotheses, and testing them by gathering more data.
Reflection
Take five minutes to reflect on the activity. You may reflect on any aspect of the activity, but if you have trouble, consider answering these questions: What was the most important thing you learned during today's class? What questions about evolution still need to be answered?