NetLogo: Rabbits, Grass, Weeds - Ecosystem Model

Uri Wilensky, Center for Connected Learning and Computer-Based Modeling, Northwestern University, Evanston, IL
Type Category
Instructional Materials
This resource, vetted by NSTA curators, is provided to teachers along with suggested modifications to make it more in line with the vision of the NGSS. While not considered to be "fully aligned," the resources and expert recommendations provide teachers with concrete examples and expert guidance using the EQuIP rubric to adapted existing resources. Read more here.



This NetLogo simulation, developed by Uri Wilensky at Northwestern University, models three populations (rabbits, grass, weeds) within an ecosystem over time. Settings within the simulation help students to make sense of the phenomena of ecosystem resilience by allowing them to mimic changes in the initial population size of rabbits, the amount of energy the rabbits require to reproduce, energy gain from food, and the growth rates of the grass and weeds. By manipulating these settings, students can ask questions and then look for evidence to support their thinking about what factors affect ecosystem equilibrium and cause populations to be either stable or unstable over time. Instructional supports include background information, instructions for using the simulation, and suggestions for extending the simulation.

Intended Audience

Educational Level
  • High School
Access Restrictions

Free access - The right to view and/or download material without financial, registration, or excessive advertising barriers.

Performance Expectations

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.

Clarification Statement: Examples of mathematical representations include finding the average, determining trends, and using graphical comparisons of multiple sets of data.

Assessment Boundary: Assessment is limited to provided data.

This resource was not designed to build towards this performance expectation, but can be used to build towards it using the suggestions provided below.

Comments about Including the Performance Expectation
Students engage in three-dimensional learning by manipulating values to explore ecosystem dynamics and the factors that may affect population equilibrium within the ecosystem. When the simulation is run, a graph of each population over time is shown. The size of the initial rabbit population may be set, allowing students to see the impact of different scales. Teachers may want to allow students to first familiarize themselves with the instructions and the simulation. Once students are comfortable with using the simulation, one suggestion is for students to ask a specific question, develop a hypothesis based on their question, and then design and execute an experiment that will provide evidence to either support or refute their hypothesis. Additional opportunities to support and defend their explanations with peers would increase the engagement and learning of this exercise. In addition, students may also be engaging in additional practices such as engaging in argument from evidence, and obtaining, evaluating, and communicating information.

Science and Engineering Practices

This resource was not designed to build towards this science and engineering practice, but can be used to build towards it using the suggestions provided below.

Comments about Including the Science and Engineering Practice
Each place in this activity where students make decisions about settings within the simulation are natural places for peer discussion, review, and defense. Teachers may want to provide students with opportunities to construct explanations as well as to review and revise their explanations; extensions of individual responses would include working as teams or sharing their thoughts in other ways with their peers. Making their thinking explicit and sharing their thinking with others will help to deepen their understanding and their engagement. Taking snapshots of their graphs at the end of each run and including these graphs in their results will help to anchor their understanding of the phenomenon of carrying capacity and the factors that affect it.

Disciplinary Core Ideas

This resource was not designed to build towards this disciplinary core idea, but can be used to build towards it using the suggestions provided below.

Comments about Including the Disciplinary Core Idea
Peer discussion/explanation/defense of ideas about factors that affect the stability of all three populations are all natural extensions of this activity. If students manipulate the different settings within the simulation, then they will be able to see how they can achieve stability within this model ecosystem. The teacher may want to ask how this model can show the influence of extreme fluctuations in conditions or the size of one particular population. The introduction of weeds may also represent an invasive species, and students may want to explore the different ways that such a species can disrupt a local ecosystem. Examples from their own geographic area may help to extend this activity to the real world.

Crosscutting Concepts

This resource was not designed to build towards this crosscutting concept, but can be used to build towards it using the suggestions provided below.

Comments about Including the Crosscutting Concept
The simulation provides an opportunity for students to compare populations of different scales by changing the initial settings of the size of the rabbit population and also by changing the amount of energy required to reproduce. Encourage discussion among students about how populations of different sizes compare. Explore the significance of the differences in scale. Other crosscutting concepts that are supported with the simulation and which could be extended are cause and effect and stability and change.

Resource Quality

  • Alignment to the Dimensions of the NGSS: This simulation supports three-dimensional learning by engaging students in mathematical thinking as they explore factors that affect ecosystem resilience of an ecosystem at different scales.

  • Instructional Supports: Because this simulation is a type of model, teachers may want to present and discuss authentic examples of stable and unstable natural populations familiar to the students prior to doing the simulation. After completing the simulation, teachers may then want to connect back to these introductory examples. In doing so, students will be supported in connecting the learning from the simulation back to real, authentic examples. The instructions provide suggestions for how to use the simulation, as well as suggested extensions. Suggestions for differentiated learning are not contained within the simulation itself, but a Concord Consortium lesson plan that uses this simulation offers one alternative for high school students who may need additional support: . In addition, a manual is available that not only describes the use of NetLogo simulations in detail, but also provides options for tech-savvy teachers to modify the simulation for their own purposes. The manual may be accessed here:

  • Monitoring Student Progress: Although there are no formal formative assessments designed within this simulation, the simulation itself elicits direct, observable evidence of three-dimensional learning; students are using mathematical practices to make sense of ecosystem resilience and the factors that limit population size while changing the settings to consider populations at different scales. Suggestions are made to help guide the instruction along paths that promote learning. Students have multiple ways to design their own experiments so that teachers can assess their understanding of the phenomenon. Screen snapshots may be taken of the simulation to provide an artifact for formative assessment.

  • Quality of Technological Interactivity: This simulation rates high in technological interactivity. If a teacher or student know how to code, the simulation may be modified and shared with a broader community of NetLogo users. It is recommended that you download the NetLogo program first. The Rabbits, Grass, Weeds model is included in the library within the downloaded application. It is NOT recommended that the model be run in a web browser.