To start the lesson, I invite the mutation experts from the day before (How Does Evolution Happen?) to remind us what a mutation is, and how mutations can be a driving factor in evolution. Instead of asking just one student from the expert pool, I ask the mutation experts to stand, and state one fact they know about mutations and their role in evolution.
Their facts may not be repeated, so they need to listen very carefully, since I will be awarding patriot bucks (school-wide incentive) to the non-expert students that "catch" repeats. This challenge gets everyone involved in either speaking or listening carefully to the information, and sets the stage for the mutations lab.
I use the mutations lab as a simple and fun way to illustrate how germline mutations can affect diversity in a population's gene pool.
The lab itself is quite simple. Each student receives the Genetic Mutation Lab Sheet. Table groups get a fun-sized bag of M&Ms (I chose fun-sized to keep the sample small - about 15 candies), count the frequency of the different colors (M&M traits), and determine the percentage of each (SP5 Using Mathematics and Computational Thinking - express the relationship between variables). This is their F1 generation. In F2, the Redhot mutation is introduced by randomly picking 5 M&Ms and replacing them with Redhots. Again, the students determine the frequency of the different traits (colors), including the mutation. In F3, a student blindly picks up 5 candies, and again determines frequency. This is repeated until the 5th generation. Here is a sample of what the results could look like.
The key idea that I want students to get is that mutations are random events. A mutation does not happen because an organism "needs" it, and if the mutation does not help or hinder the species it may remain in the gene pool or not. Again this is totally random. This idea is evidenced as the students analyze the results from other tables (SP4 Analyzing and Interpreting Data) in questions 2 and 3 of the lab sheet, and why it is imperative that students don't "cheat" when blindly picking up candies during the lab.
Questions 4, 5 and 6 ask students what would happen when selection takes over. As students answer these questions, they are evaluating their results to form hypothesis (SP6 Constructing Explanations and Designing Solutions). Discussion during this part is a key component of the lesson, and I circulate the room asking students to defend their explanations (SP7 Engaging in Argument from Evidence).
Watch as the students progress through the lab from sampling to understanding.
For classroom management purposes, and to encourage all students to ensure that the work from everyone is up to standards, I tell the students that I will only take one lab sheet per table to be graded. This means that whichever sheet I choose must be complete, that whatever is written down on all sheets represents the table's consensus, and that it reflects the table's participation in the day's activity.
Note to teachers: As I started to analyze the student work (SW1, SW2, SW3) I noticed that there was some confusion in questions 5 and 6. The original names of the organisms involved were too similar, so the students were unclear on who eats what making their benefits assessment somewhat muddled. The lab sheet included in this lesson is the "corrected" version.
To close this lesson I display a picture of Wolverine (from X-Men), and ask the students,
Would Wolverine be able to pass on his adamantium skeleton to his children?
The answer is no, the adamantium was added to him; it is not a germline mutation.
Note to teachers: You might wonder why I chose this question, instead of one more related to the content. Sometimes I put in a pop-culture question to encourage my students to feel that science is not always about "the work", and that science concepts can be used in fun ways.
I do have to say that today I was given a lesson in the X-Men folklore that I was unaware of. Apparently my response to the Wolverine question is outdated. In newer versions the X-Men saga, the adamantium actually caused a germline mutation and Wolverine has a child born with an adamantium skeleton.