Interspecific Interactions: Competition and Predation

Active learning works for interspecific interactions because students need to see how small changes in traits or behaviors ripple through food webs. Simulation games and case studies let them test assumptions in real time, turning abstract models like Lotka-Volterra into observable patterns. Movement, collaboration, and immediate feedback make the invisible processes of competition and predation visible and memorable.

• Grade 12
• Biology
• 4 activities
• 30 min–50 min

Learning Objectives

1. Compare the ecological outcomes of competitive exclusion and resource partitioning in simulated ecosystems.
2. Explain the cyclical dynamics of predator-prey populations using graphical representations and mathematical models.
3. Analyze the ripple effects of removing a keystone species on community structure and trophic levels.
4. Evaluate the co-evolutionary adaptations that arise from predator-prey interactions.
5. Predict the impact of altered interspecific interactions on ecosystem stability.

Simulation Game

⏱ 45 min·Small Groups

Simulation Game: Predator-Prey Cycles

Scatter paper 'prey' on the floor; 'predator' students collect as many as possible in 1 minute, then switch roles for multiple generations. Vary predator numbers and record data. Graph population trends to identify cycles.

Prepare & details

How does the loss of a keystone species trigger a trophic cascade?

Facilitation Tip: For the Predator-Prey Cycles simulation, circulate with a timer and call out the next generation loudly so students stay synchronized without constant prompting.

Setup: Flexible space for group stations

Materials: Role cards with goals/resources, Game currency or tokens, Round tracker

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

Case Study Analysis

⏱ 50 min·Small Groups

Case Study Analysis: Yellowstone Wolves

Provide data sets and videos on wolf reintroduction effects on elk, vegetation, and beavers. In groups, map the trophic cascade and predict changes if wolves were removed. Share findings in a class jigsaw.

Prepare & details

In what ways does niche partitioning reduce competition between overlapping species?

Facilitation Tip: During the Yellowstone Wolves case study, assign roles so each student contributes to the flow diagram while someone else narrates the changes aloud.

Setup: Groups at tables with case materials

Materials: Case study packet (3-5 pages), Analysis framework worksheet, Presentation template

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

Placemat Activity

⏱ 30 min·Pairs

Placemat Activity: Resource Partitioning Cards

Distribute cards representing food resources and species traits. Pairs assign traits to niches, first modeling full competition leading to exclusion, then partitioning to show coexistence. Discuss adaptations.

Prepare & details

Analyze the co-evolutionary arms race between predators and prey.

Facilitation Tip: When running the Resource Partitioning Cards activity, ask students to swap cards after each round to prevent fixed pairings from skewing their observations.

Setup: Groups at tables with placemat papers

Materials: Pre-drawn placemat papers (one per group), Central question/prompt, Markers

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

Experiential Learning

⏱ 35 min·Pairs

Graphing: Lynx-Hare Data

Provide historical population graphs. Individually plot new data points from tables, then in pairs analyze cycle phases and predict next peaks. Connect to Lotka-Volterra.

Prepare & details

How does the loss of a keystone species trigger a trophic cascade?

Facilitation Tip: In the Graphing Lynx-Hare Data activity, provide colored pencils for each group and require them to label axes and units before plotting to reduce careless errors.

Setup: Varies; may include outdoor space, lab, or community setting

Materials: Experience setup materials, Reflection journal with prompts, Observation worksheet, Connection-to-content framework

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

Teaching This Topic

Start with the simplest model first: show students a two-species competition scenario on the board, then let them run the simulation to watch competitive exclusion unfold in minutes, not semesters. Avoid overloading them with equations early; build intuition from observed patterns. Research shows that students grasp keystone species best when they trace effects forward and backward through food webs themselves, rather than just listening to a lecture about them.

What to Expect

Successful learning is shown when students can explain why similar species coexist, trace the causes of population cycles, and predict ecosystem-wide effects when a keystone species is removed. They should use visual models, data, and real-world examples to justify their reasoning, not just recall definitions.

Watch Out for These Misconceptions

Common Misconception

During the Resource Partitioning Cards activity, watch for students who assume competition always leads to extinction.

What to Teach Instead

Ask them to adjust the cards to reduce overlap and observe how coexistence becomes possible; have them calculate the percentage change in shared resources to quantify their adjustments.

Common Misconception

During the Predator-Prey Cycles simulation, watch for students who expect predator numbers to rise and fall exactly with prey numbers in the same generation.

What to Teach Instead

Pause the simulation after round three to ask groups to sketch predicted values for the next round, then compare their predictions to the actual results to highlight the lag effect.

Common Misconception

During the Yellowstone Wolves case study discussion, watch for students who assume keystone species only affect their direct prey.

What to Teach Instead

Give each group a colored marker and have them trace arrows from wolves to scavengers, plants, and birds on the flow diagram to reveal indirect effects before sharing out.

Assessment Ideas

Quick Check

After the Resource Partitioning Cards activity, provide two species profiles and ask students to predict whether competitive exclusion or resource partitioning is more likely, citing traits from their card set to justify their answer.

Discussion Prompt

After the Predator-Prey Cycles simulation, pose the question about a new predator’s introduction and facilitate a class discussion where students reference their plotted cycles to support their predictions about population changes.

Exit Ticket

During the Yellowstone Wolves case study, have students draw a simple food web showing a keystone species, then add an arrow for its removal and write one sentence predicting a trophic cascade based on the flow diagram they helped create.

Extensions & Scaffolding

• Challenge students to design a new predator-prey simulation with a third species that alters the cycle, then present their model to the class.
• Scaffolding: Provide pre-labeled graphs for the Lynx-Hare activity so students focus on interpreting trends rather than plotting.
• Deeper exploration: Have students research and present a real-world example of resource partitioning not covered in class, using images or short videos to illustrate niche differentiation.

Key Vocabulary

Competitive Exclusion Principle	States that two species competing for the exact same limited resources cannot coexist indefinitely in the same ecological niche. One species will eventually outcompete the other.
Resource Partitioning	The division of limited resources by species that coexist by using them in different ways, at different times, or in different locations. This reduces direct competition.
Keystone Species	A species that has a disproportionately large effect on its environment relative to its abundance. Its removal can cause significant changes in community structure.
Trophic Cascade	An ecological process that starts at the top of the food chain and tumbles down to lower levels. Often triggered by the removal or addition of a top predator or keystone species.
Co-evolution	The influence of closely associated species on each other in their evolution. This is often seen in predator-prey relationships, leading to an 'arms race' of adaptations.