Activity 01
Simulation Game: Genetic Drift Beans
Provide pairs with 20 beans (10 red, 10 white) as alleles. Students randomly select pairs to form 'offspring' genotypes over 5 generations, recording frequency changes. Discuss how random sampling mimics drift in small populations.
What forces can shift allele frequencies in a population over time, and which tend to have the greatest impact?
Facilitation TipDuring Genetic Drift Beans, have students record allele counts after each generation and graph the results to visualize how randomness affects small populations.
What to look forPresent students with a population's genotype counts (e.g., 50 AA, 100 Aa, 50 aa). Ask them to calculate the allele frequencies of A and a, and then the expected genotype frequencies under Hardy-Weinberg equilibrium. This checks their ability to apply the basic equations.
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Activity 02
Stations Rotation: Hardy-Weinberg Calculations
Set up stations with sample data sets for allele frequencies. Groups calculate p, q, expected genotypes, and chi-square tests to check equilibrium. Rotate every 10 minutes, then share deviations caused by forces.
How do populations maintain genetic variation even when selection pressure acts against certain alleles?
Facilitation TipAt Hardy-Weinberg stations, provide colored pencils for students to shade Punnett squares and genotype grids, making the math visible and organized.
What to look forPose the scenario: 'Imagine a small, isolated population of island birds where a new predator is introduced. Which evolutionary force (drift, selection, mutation, gene flow) do you predict will have the most immediate and significant impact on allele frequencies, and why?' Facilitate a class discussion comparing student reasoning.
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Activity 03
Role-Play: Natural Selection pressures
Assign students alleles via cards. Introduce selection events like 'predator hunts' where certain genotypes survive better. Track frequency shifts over rounds and graph changes.
How might the genetic diversity of a small, isolated population change over generations , and what events could accelerate or reverse this?
Facilitation TipIn the Natural Selection role-play, assign roles clearly and circulate to ensure students connect their individual survival to population-level allele changes.
What to look forProvide students with a brief description of a hypothetical population facing a specific environmental change (e.g., a drought affecting a plant species). Ask them to identify which allele frequencies are likely to increase or decrease and to name the primary evolutionary force driving this change.
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Activity 04
Data Analysis: PTC Taster Survey
Conduct class taste test for PTC paper to find real allele frequencies. Students calculate HW expectations, test fit with chi-square, and infer population forces.
What forces can shift allele frequencies in a population over time, and which tend to have the greatest impact?
Facilitation TipDuring the PTC Taster Survey, have students pool class data to calculate p and q, then compare their results to global allele frequencies for context.
What to look forPresent students with a population's genotype counts (e.g., 50 AA, 100 Aa, 50 aa). Ask them to calculate the allele frequencies of A and a, and then the expected genotype frequencies under Hardy-Weinberg equilibrium. This checks their ability to apply the basic equations.
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Generate Complete Lesson→A few notes on teaching this unit
Teach Hardy-Weinberg as a null model first, then immediately disrupt it with simulations to show how real populations evolve. Avoid starting with complex equations; instead, let students derive p + q = 1 from counting alleles in a simple population. Research shows that students grasp evolutionary change better when they experience randomness firsthand, so prioritize drift simulations before selection scenarios to reduce deterministic thinking about evolution.
Students will confidently explain how allele frequencies shift under different evolutionary forces, calculate p and q values accurately, and connect simulations to real-world population scenarios. Success looks like students using the Hardy-Weinberg equations as tools, not just formulas, and identifying when equilibrium is disrupted.
Watch Out for These Misconceptions
During Natural Selection Role-Play, listen for students to say individuals change their own traits to survive.
Pause the role-play and ask students to record the genotypes of survivors before reproduction. Debrief by having them compare these genotypes to the next generation’s allele frequencies to show evolution happens at the population level.
During Genetic Drift Beans, students may assume that advantageous alleles always increase in frequency.
After each round, have students pause to predict which alleles will survive in the next generation, then compare predictions to actual results to highlight the role of chance in small populations.
During Hardy-Weinberg Calculations, students often think the model describes how evolution occurs.
After completing calculations, ask students to alter the genotype counts slightly and recalculate to see how quickly equilibrium is disrupted, reinforcing it as a baseline, not a process.
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