During the lesson, students use M&M's to represent sampling from a population of haploid, sexually reproducing organisms, creating a small “founder” population from a larger “source” population. They then plot their data and carry out the following discussions:
(Text from the Yale Center for Scientific Teaching's Teachable Tidbits).
Below is a more detailed breakdown of the activity:
Session 1 |
|
Pre-class |
Previous unit should have covered mutation and natural selection |
10 minutes
|
Start of class: clicker quiz reviewing concepts of natural selection - formative assessment |
8 minutes
|
Introduction of the pattern of the frequency of Huntington’s disease worldwide vs. Afrikaners Students discuss and formulate hypotheses |
35 minutes |
M&M activity 1. introduction of activity, taking time to distinguish it from the Huntington’s example - give students time to read instructions
2. students follow directions to create splinter populations, begin recording data and graphing their results - discussion of their results so far and why not everyone got a frequency of 50% - students make predictions about how frequencies will change if the population size is constrained for multiple generations - formative assessment
3. students continue following directions to produce a total of 5 generations, recording the data and graphing their results discussion of results highlighting: - drift is a mechanism of evolution - differences with natural selection - formative assessment |
12 minutes |
Follow up on Huntington’s disease – discuss the example of Huntington’s disease in light of the exercise on drift Discussion should include - how might students want to modify their initial hypotheses - additional information to distinguish drift and natural selection - explicit description of the Huntington’s example as a founder effect - formative assessment |
9 minutes
|
Introduction of simulation program, run simulation with larger population size and have students discuss the difference between the simulation results and their M&M results. - PopG can be downloaded at: http://evolution.gs.washington.edu/popg/ - formative assessment |
1 minute
|
Assign homework that will involve students using the simulation program and explaining the differences in the results due to the effects of selection and drift - summative assessment |
Session 2 |
|
Pre-class |
Homework assignment completed |
In Class |
- Formative assessment (clicker questions) focused on simulation results. - Discussion of homework - Could present a modification of a graph from the Dobzhansky and Pavlovsky (1957) paper and ask students to interpret the data and develop hypotheses. Modified graph can be found at: http://www.blackwellpublishing.com/ridley/a-z/Genetic_drift.asp - Discuss conservation case study demonstrating a bottleneck in cape buffalo |
presentation.pptx | 4.34 MB | |
agenda.docx | 14 KB | |
instructions.docx | 12 KB |