Biology · 9th Grade

Active learning ideas

Community Interactions: Competition and Predation

Active learning engages students directly with the dynamic relationships in ecological communities. By modeling competition and predation through simulations and data analysis, students move beyond memorization to observe firsthand how populations interact and adapt over time.

• Common Core State Standards
• HS-LS2-6
• HS-LS2-2

• 20–45 min
• Pairs → Whole Class
• 4 activities

Activity 01

• Role Play
• 45 min · Pairs

Graphing Lab: Predator-Prey Population Cycles

Using Hudson Bay Company records of lynx and snowshoe hare pelts (a classic proxy for population size), students graph both populations on the same axes and analyze the lagged oscillations. They identify which population leads the cycle, explain the cause-and-effect relationship that sustains the cycle, and predict what happens if a secondary prey source for lynx is added.

Explain how the competitive exclusion principle shapes community diversity.

Facilitation Tip

During the Graphing Lab, circulate to ensure students correctly label axes and include a key for predator and prey lines before they start plotting data.

What to look for

Provide students with two hypothetical species descriptions, including their food sources and habitat preferences. Ask them to write a short paragraph predicting whether these species would compete, and if so, whether they might coexist based on niche partitioning.

• Apply
• Analyze
• Evaluate
• Social Awareness
• Self-Awareness

Activity 02

• Simulation Game
• 40 min · Small Groups

Simulation Game: Competitive Exclusion Experiment

Based on G.F. Gause's paramecium experiments, two 'species' of students compete for the same resource chips with slightly different success rates. After 10 rounds, students graph population sizes, observe competitive exclusion, and then modify the experiment by adding a second resource type to simulate resource partitioning and test whether coexistence becomes possible.

Analyze how defensive adaptations in prey influence predator evolution.

Facilitation Tip

For the Competitive Exclusion Experiment, assign roles so students rotate between setting up trials, recording data, and analyzing results.

What to look for

Pose the question: 'Imagine a new predator is introduced into a forest ecosystem with established prey populations. What are two specific adaptations the prey might evolve over time, and how would these adaptations then influence the predator's own evolution?' Facilitate a class discussion where students share their ideas.

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

Activity 03

• Gallery Walk
• 35 min · Small Groups

Gallery Walk: Coevolution in Action

Create stations featuring paired coevolved predator-prey relationships (cheetah and Thomson's gazelle speed, monarch butterfly and milkweed cardenolide toxins, mimic octopus and predators). At each station, students identify the evolutionary pressure, list one defensive and one offensive adaptation the relationship has produced, and note how removing one species would affect the other's evolution.

Differentiate between interspecific and intraspecific competition.

Facilitation Tip

In the Gallery Walk, provide sentence starters on posters to guide students in writing specific examples of coevolution they observe.

What to look for

On an index card, have students define 'interspecific competition' and 'intraspecific competition' in their own words. Then, ask them to provide one real-world example for each type of competition they might observe in a local park or backyard.

• Understand
• Apply
• Analyze
• Create
• Relationship Skills
• Social Awareness

Activity 04

• Think-Pair-Share
• 20 min · Pairs

Think-Pair-Share: Classifying Competition

Students receive six competition scenarios and classify each as interspecific or intraspecific. They explain to a partner why intraspecific competition is generally more intense (identical resource requirements) and discuss one example from a US ecosystem where intraspecific competition has shaped observable behavior or morphology.

Explain how the competitive exclusion principle shapes community diversity.

What to look for

Provide students with two hypothetical species descriptions, including their food sources and habitat preferences. Ask them to write a short paragraph predicting whether these species would compete, and if so, whether they might coexist based on niche partitioning.

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

A few notes on teaching this unit

Teaching this topic works best when students physically manipulate variables and observe immediate outcomes. Avoid relying solely on textbook examples; simulations let students test predictions and see exceptions like resource partitioning in real time. Research shows that students grasp the concept of dynamic equilibrium more deeply when they graph fluctuating populations themselves rather than reading about it.

Students will explain how competition and predation shape population cycles and community structure using evidence from their simulations and observations. They will also predict outcomes when species partition resources or face competitive exclusion.

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Watch Out for These Misconceptions

• Predators always reduce prey populations toward extinction.

  During the Graphing Lab: Students analyze real predator-prey oscillation data and adjust their line graphs to show how declines in prey lead to predator declines, then prey recovery. Point out the peaks and troughs to reinforce the cyclical nature of these interactions.

• Competition always results in one species winning and the other going extinct.

  During the Competitive Exclusion Experiment: After students observe competitive exclusion in the initial simulation, have them modify variables to include resource partitioning, such as different feeding times or microhabitats, and observe how coexistence becomes possible.

• Defensive adaptations are always physical structures like shells or spines.

  During the Gallery Walk: Provide a set of adaptation examples that include behavioral strategies like alarm calls or feigning death. Have students sort these into categories and discuss which are most effective in different scenarios.

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Methods used in this brief

• Role Play
• Simulation Game
• Gallery Walk
• Think-Pair-Share