Lyme Disease Ecology: The Acorn Connection
Estimated Time: 45-60 minutes Materials: Internet-connected device, Lyme Disease Ecology Simulation, graphing paper or digital spreadsheet (optional)
Part 1: Engage (Anchoring Phenomenon)
Phenomenon: An interactive mathematical model exploring the ecological cascade in New England forests, demonstrating how oak masting, predator populations, and winter severity drive mouse populations, tick proliferation, and human Lyme disease risk.
Consider the following scenario: A forest experiences an unusually massive acorn drop one autumn (a “mast” year). Two years later, the nearby town experiences a significant spike in Lyme disease cases among its human population.
- What questions do you have about this scenario? _____
- Based on your prior knowledge of ecosystems, what might connect acorns (a plant part) to Lyme disease (a human illness)? _____
Part 2: Explore (Simulation Investigation)
Open the Lyme Disease Ecology Simulation.
Familiarize Yourself with the Controls and Outputs
- Controls: You can adjust Acorn Production (10-100), Predator Density (0-100), and Deer Population (10-100).
- Outputs: Observe the 4-Year Ecological Data Log, which graphs the populations of Acorns, Mice, and Questing Nymphs over time.
Investigation 1: The Impact of Acorns
- Set the Predator Density and Deer Population to intermediate levels (e.g., 50).
- Set Acorn Production to a low level (e.g., 20). Click the run button and observe the 4-year data log.
- Increase Acorn Production to a high level (e.g., 90). Run the simulation again.
- Record your observations in the table below.
| Variable Changed | Effect on Mice Population | Effect on Questing Nymphs |
|---|---|---|
| Low Acorn Production | _____ | _____ |
| High Acorn Production | _____ | _____ |
Investigation 2: The Role of Predators
- Keep Acorn Production high and Deer Population at an intermediate level.
- Set Predator Density to a low level (e.g., 10). Run the simulation.
- Increase Predator Density to a high level (e.g., 90). Run the simulation.
- Record how changing the predator density affects the mice and questing nymph populations. _____
Part 3: Explain (Sensemaking)
Using the data you collected:
- Describe the mathematical relationship (trend) you observed between acorn production and the white-footed mouse population. Why does this relationship exist? _____
- How does the population of mice affect the population of questing nymphs? Explain this interaction in terms of ecosystem dynamics. _____
- Based on the simulation, does a change in acorn production have an immediate effect on the nymph population, or is there a delay? Explain why using evidence from the graphs. _____
Part 4: Elaborate/Evaluate (Argumentation & Modeling)
Student Deliverable: Construct a scientific argument supported by mathematical representations from the simulation.
Prompt: The local health department wants to predict Lyme disease risk for the upcoming year. They have noted that last year, there was a very low acorn crop, but predator density has also been very low due to habitat fragmentation. Using the simulation as a model, predict the Lyme disease risk (indicated by the number of questing nymphs) for the upcoming year. Write a paragraph explaining your prediction. Your argument must include:
- A clear claim about the expected Lyme disease risk (high, medium, or low).
- Specific numerical data (trends or averages) from the simulation to support your claim.
- An explanation of how interactions between different scales of the ecosystem (e.g., macroscopic predators vs. microscopic disease transmission via ticks) are involved.
Teacher Notes
NGSS Alignment:
- Performance Expectation: HS-LS2-2: Use mathematical representations to support and revise explanations based on evidence about factors affecting biodiversity and populations in ecosystems of different scales.
- Science and Engineering Practices (SEPs): Using Mathematics and Computational Thinking. Students use mathematical representations (graphs) of phenomena to support explanations.
- Disciplinary Core Ideas (DCIs): LS2.A: Interdependent Relationships in Ecosystems; LS2.C: Ecosystem Dynamics, Functioning, and Resilience.
- Crosscutting Concepts (CCCs): Scale, Proportion, and Quantity.
Evidence Statements: This task provides evidence for the following observable features of student performance:
- Representation (1.a.i, 1.a.ii, 1.b.i, 1.b.ii, 1.b.iii): Students identify and describe components in mathematical representations (graphs of acorns, mice, nymphs) relevant to factors affecting biodiversity. They identify explanations that populations vary as a function of biological dynamics and that ecosystems exist at various scales interacting with each other (e.g., microscopic Lyme bacteria, macroscopic deer and acorns).
- Mathematical Modeling (2.a): Students use the simulation’s graphs to identify changes over time in the numbers of organisms.
- Analysis (3.a.i, 3.a.ii, 3.a.iii, 3.b): Students use the analysis of the graphs to identify important factors (acorns, predators) determining population numbers, using this as evidence to support explanations for the effects of living/nonliving factors. They describe how factors at one scale (acorn production) cause observable changes at a different scale (tick nymphs).
- Revision (4.a): Students can revise their explanations based on new evidence (e.g., changes in predator density affecting the expected outcome of an acorn mast).