Teacher Notes
Targeted NGSS Performance Expectation: HS-LS2-6: Evaluate the claims, evidence, and reasoning that the complex interactions in ecosystems maintain relatively consistent numbers and types of organisms in stable conditions, but changing conditions may result in a new ecosystem.
Three-Dimensional Learning:
- Science and Engineering Practices (SEPs): Engaging in Argument from Evidence - Evaluate the claims, evidence, and reasoning behind currently accepted explanations or solutions to determine the merits of arguments.
- Disciplinary Core Ideas (DCIs): LS2.C: Ecosystem Dynamics, Functioning, and Resilience - A complex set of interactions within an ecosystem can keep its numbers and types of organisms relatively constant over long periods of time under stable conditions. If a modest biological or physical disturbance to an ecosystem occurs, it may return to its more or less original status (i.e., the ecosystem is resilient), as opposed to becoming a very different ecosystem. Extreme fluctuations in conditions or the size of any population, however, can challenge the functioning of ecosystems in terms of resources and habitat availability.
- Crosscutting Concepts (CCCs): Stability and Change - Much of science deals with constructing explanations of how things change and how they remain stable.
Evidence Statements Addressed: Student work demonstrates they can:
- Identify the given explanation that complex interactions in ecosystems maintain relatively consistent numbers and types of organisms in stable conditions, but changing conditions may result in a new ecosystem.
- Identify potential additional evidence that is relevant to the evaluation, including factors that affect biodiversity and changes in the numbers of species and organisms in an ecosystem that has been subject to a modest or extreme change in ecosystem conditions.
- Evaluate and critique the logic of the reasoning, including the relationship between degree of change and stability in ecosystems, and the utility of the reasoning in supporting the explanation of how extreme fluctuations in conditions or the size of any population can challenge the functioning of ecosystems.
Implementation Details:
- Estimated Time: 45-60 minutes
- Materials: Device with internet access (one per student or pair), simulation URL.
Student Task: Secondary Succession in El Yunque
Engage
El Yunque National Forest in Puerto Rico is a tropical rainforest characterized by a mature canopy of large, slow-growing Tabonuco trees. However, the island is periodically struck by powerful hurricanes that can completely strip the mature canopy and devastate the forest structure. Following a major hurricane, the forest floor suddenly receives direct sunlight.
- Prediction: Based on what you know about plant growth and competition for resources, predict what types of plants will be the first to regrow and dominate the area immediately after the hurricane. Why? _____
Explore
Launch the El Yunque Secondary Succession Simulation.
- Familiarize yourself with the controls. You will see a “Hurricane” button, a “Play” button, and tabs for “Population Dynamics” and “Construct Explanation (SEP)”.
- Click the “Hurricane” button to simulate a major disturbance clearing the mature canopy.
- Click “Play” to start the simulation and observe the changes over time. You can pause the simulation at any point.
- Switch to the “Population Dynamics” tab to observe the graph showing the population counts of Yagrumo (pioneer species) and Tabonuco (climax species) over time.
Collect data from the simulation by pausing at regular intervals (e.g., Year 10, 20, 30, etc.) and recording the population of each tree type in the table below.
| Year | Yagrumo Population | Tabonuco Population |
|---|---|---|
| 0 | ||
| 10 | ||
| 20 | ||
| 30 | ||
| 40 | ||
| 50 |
Explain
- Analyze the Data: Based on your observations and the data you collected, describe the population trends of the Yagrumo and Tabonuco trees. Which tree dominates first, and which tree dominates later? _____
- Evaluate Claims & Reasoning: A classmate claims that the Yagrumo tree is better adapted to survive in El Yunque than the Tabonuco tree because its population explodes so quickly after a hurricane. Evaluate this claim. Does the evidence from the simulation fully support this reasoning? Why or why not? Consider factors like growth rate, lifespan, and shade tolerance. _____
- Switch to the “Construct Explanation (SEP)” tab in the simulation. Based on the simulation data, construct a scientific explanation detailing the process of secondary succession in El Yunque. How do the different traits of the Yagrumo (fast growth, shade intolerance) and Tabonuco (slow growth, shade tolerance) allow them to dominate at different stages after the hurricane? Discuss competition for sunlight. Ensure you submit your explanation.
Elaborate / Evaluate
Ecosystem Resilience: The simulation demonstrates secondary succession following a hurricane. Based on the DCI (LS2.C) and the evidence from the simulation, is the El Yunque ecosystem resilient? Explain your reasoning, making sure to describe the difference between the initial change in the ecosystem and its long-term stability. _____
Extension: How might the succession process change if hurricanes began occurring much more frequently (e.g., every 15 years instead of every 60 years)? Support your prediction using evidence about the lifespans and growth rates of the Yagrumo and Tabonuco trees. _____