Biology · 11th Grade

Active learning ideas

Hardy-Weinberg Equilibrium and Population Genetics

Active learning works for Hardy-Weinberg Equilibrium because students often confuse the theoretical baseline with real-world conditions. Hands-on calculations, simulations, and case studies help them see why equilibrium is rare and why deviations matter. This approach turns abstract equations into concrete evidence of evolutionary change.

• Common Core State Standards
• HS-LS4-2

• 20–50 min
• Pairs → Whole Class
• 4 activities

Activity 01

• Problem-Based Learning
• 50 min · Small Groups

Collaborative Problem Set: Hardy-Weinberg Calculations

Groups work through a tiered problem set: calculating p and q from genotype counts, predicting expected genotype frequencies, then comparing expected to observed values and deciding whether the population is in equilibrium. Each group presents one problem, explains their reasoning, and identifies which H-W condition may be violated if the population deviates.

Explain the five conditions required for a population to be in Hardy-Weinberg equilibrium.

Facilitation Tip

For the Collaborative Problem Set, assign small groups the same starting data but have each group violate a different Hardy-Weinberg condition to compare outcomes.

What to look for

Present students with a population data set showing allele counts (e.g., 50 individuals, 60 'A' alleles, 40 'a' alleles). Ask them to calculate the allele frequencies (p and q) and then the expected genotype frequencies (p², 2pq, q²) using the Hardy-Weinberg equations. Review calculations as a class.

• Analyze
• Evaluate
• Create
• Decision-Making
• Self-Management
• Relationship Skills

Activity 02

• Simulation Game
• 40 min · Whole Class

Simulation Game: Population Genetics with Playing Cards

Students simulate a random mating population using a card deck where red cards represent allele A1 and black cards represent allele A2. They draw pairs to simulate mating, record genotypes, and track allele frequencies across five generations. They compare results to H-W predictions and discuss why their simulated population drifts even without intentional selection.

Analyze how deviations from Hardy-Weinberg equilibrium indicate that evolution is occurring.

Facilitation Tip

In the Playing Cards Simulation, remind students to record allele counts after each generation but before selection, drift, or migration occurs.

What to look for

Pose a scenario: 'A population of island birds shows a significant decrease in the frequency of the allele for dark feathers over 50 years.' Ask students: 'Which of the five Hardy-Weinberg conditions is most likely being violated, and why? What type of evolutionary force might be at play?'

• Apply
• Analyze
• Evaluate
• Create
• Social Awareness
• Decision-Making

Activity 03

• Think-Pair-Share
• 20 min · Pairs

Think-Pair-Share: Which Condition Is Violated?

Students receive five brief scenarios , an island population hit by a hurricane, a population where males prefer light-colored females, a population that receives migrants from a neighboring region. Pairs identify which Hardy-Weinberg assumption each scenario violates, explain the consequence for allele frequencies, and predict the direction of change.

Calculate allele and genotype frequencies using the Hardy-Weinberg equations.

Facilitation Tip

During the Think-Pair-Share, circulate and listen for students who correctly identify violations before revealing the answer to the whole class.

What to look for

Provide students with a table of observed genotype counts for a population and the calculated allele frequencies. Ask them to: 1. Calculate the expected genotype frequencies using p² + 2pq + q² = 1. 2. Write one sentence explaining whether the population appears to be in Hardy-Weinberg equilibrium based on their calculations.

• Understand
• Apply
• Analyze
• Self-Awareness
• Relationship Skills

Activity 04

• Case Study Analysis
• 30 min · Small Groups

Case Study Analysis: PKU and Carrier Frequency

Groups receive the incidence of phenylketonuria (PKU) in the US population (approximately 1 in 10,000 births). Using Hardy-Weinberg, they calculate the expected carrier frequency, compare it to the homozygous recessive frequency, and discuss why knowing the carrier frequency matters for newborn screening programs and genetic counseling.

Explain the five conditions required for a population to be in Hardy-Weinberg equilibrium.

What to look for

Present students with a population data set showing allele counts (e.g., 50 individuals, 60 'A' alleles, 40 'a' alleles). Ask them to calculate the allele frequencies (p and q) and then the expected genotype frequencies (p², 2pq, q²) using the Hardy-Weinberg equations. Review calculations as a class.

• Analyze
• Evaluate
• Create
• Decision-Making
• Self-Management

A few notes on teaching this unit

Teach Hardy-Weinberg as a tool for asking questions, not just calculating numbers. Emphasize that the equations count alleles, not rank them by dominance. Use real data sets to show how scientists apply the null hypothesis to detect evolution. Avoid presenting the five conditions as a checklist; instead, frame them as forces that disrupt genetic stability, which students will explore through simulations and case studies.

Students will confidently calculate allele and genotype frequencies, explain which Hardy-Weinberg condition is violated in a scenario, and justify their reasoning with data. They will also connect population genetics concepts to real-world health cases like PKU.

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Watch Out for These Misconceptions

• During the Simulation: Population Genetics with Playing Cards, watch for students who assume the deck of cards represents real allele frequencies without checking the starting conditions.

  Before starting the simulation, have groups count and record the initial allele frequencies (e.g., red and black cards as alleles) and confirm that p + q = 1. Refer back to these recorded values when students claim their population is in equilibrium.

• During the Collaborative Problem Set: Hardy-Weinberg Calculations, watch for students who assume p always represents the dominant allele and q the recessive allele.

  Provide a data set where the dominant allele is rare (e.g., p = 0.2 for a dominant allele) and ask students to calculate genotype frequencies. After calculations, ask why a dominant allele can be rare and what this means for allele frequencies in the population.

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Methods used in this brief

• Problem-Based Learning
• Simulation Game
• Think-Pair-Share
• Case Study Analysis