Population Explosion

The Concord Consortium
Type Category
Instructional Materials
Model , Activity , Interactive Simulation
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.



Population Explosion is a computer simulation which allows students to manipulate factors to see what happens over time to a population of sheep within an enclosed field. As the simulation runs, a graph shows the dynamic relationship between the sheep population size and their primary food resource, grass. Students can control factors such as initial number of sheep, grass regrowth rate, gain from food, and birthrate. Predation is represented by a “reaper” button which may also be controlled. The speed of the simulation can be set so that students can see more clearly what happens over time, or collect data more quickly, depending on how fast the simulation runs. Directions and a suggested simulation sequence are provided along with prompts so that students can pause and consider their results. A space within the simulation is provided for students to record observations and answers to the prompts. For each step in this suggested sequence, students take a snapshot of graphs they have created and store them in an album. At the end of the activity analysis questions help students connect the activity to wild populations. An optional extension exercise is also suggested. An important note is that user data is not saved unless students and teachers sign up through an available project portal called “Innovative Technology in Science Inquiry”: http://itsi.portal.concord.org/home

Intended Audience

Educator and learner
Educational Level
  • High School
Access Restrictions

Free access with user action - The right to view and/or download material without financial barriers but users are required to register or experience some other low-barrier to use.

Performance Expectations

HS-LS2-1 Use mathematical and/or computational representations to support explanations of factors that affect carrying capacity of ecosystems at different scales

Clarification Statement: Emphasis is on quantitative analysis and comparison of the relationships among interdependent factors including boundaries, resources, climate, and competition. Examples of mathematical comparisons could include graphs, charts, histograms, and population changes gathered from simulations or historical data sets.

Assessment Boundary: Assessment does not include deriving mathematical equations to make comparisons.

This resource appears to be designed to build towards this performance expectation, though the resource developer has not explicitly stated so.

Comments about Including the Performance Expectation
This simulation does not allow for students to compare ecosystems of different scales; it does, however, allow students to manipulate variables to understand multiple factors that will impact population size over time and to see how carrying capacity may be reached. It may be helpful to allow students to familiarize themselves with the simulation until they have a good sense of what each control does. Students will deepen their understanding of factors that influence carrying capacity if they are thoughtful in how they use the simulation. Consider ways to structure the activity so that students ask questions first and then see how they can use the simulation to answer their questions. It is also possible to use the simulation to provide evidence to support claims. Students can be encouraged to think about a particular factor, such as predation, and make a statement about how they think this one factor will affect the carrying capacity of the ecosystem for the sheep population. Providing plenty of opportunities for students to share their explanations with one another will also deepen their understanding about how factors such as predation, birth rate, death rate, and food availability affect the carrying capacity.

Science and Engineering Practices

This resource appears to be designed to build towards this science and engineering practice, though the resource developer has not explicitly stated so.

Comments about Including the Science and Engineering Practice
Prior to using the simulation, ask students about their understanding of how different factors may affect a population within an enclosed area. Ask them what they think will be most important in determining whether or not a population survives. By asking students to first think about carrying capacity, the simulation can provide specific quantitative support for their explanations. Help the students to focus on the graph and to be able to explain how it is relevant to support explanations of factors. Do they think that the graph reflects how one factor may be more significant than another? How does the graph change over time with different factors? Using the snapshot feature within the simulation will allow students to collect their data and to make comparisons when they change different variables. This process can be iterative, as the activity lends itself for expansion. If students have different ideas about potential outcomes, then different teams can design their own simulations to see if their ideas are supported. Good peer discussions will provide ways for students to gain a deeper understanding of their results. Encourage students to set the controls at specific levels so they can see how each factor influences the population over a range of values.

Disciplinary Core Ideas

This resource appears to be designed to build towards this disciplinary core idea, though the resource developer has not explicitly stated so.

Comments about Including the Disciplinary Core Idea
Population Explosion is well designed to support this core idea, although students may need to be reminded that it is a simplified simulation without the complexity of a natural dynamic ecosystem. One advantage of a simulation is that simplification helps us to better understand how systems work. Students should be encouraged to use all the provided controls so that they can better understand the factors that affect abundance. Predation can be mimicked (and controlled) by use of the “reaper” button. The graph should be used to provide evidence and support for students' explanations. Encourage students to think critically about each factor and why it might have the influence that it does. For example, ask students about the relationship between the number of sheep and the amount of grass. What would this look like in the wild with a natural population? Do they know of any examples? Supplement this lesson with real examples of populations exceeding their carrying capacity. One example is a fact sheet about mule deer in Utah which may be found at: http://wildlife.utah.gov/hunting/pdf/mdwg/mdwg-5_carrying_capacity.pdf. Within Population Explosion a link is provided for NetLogo: http://ccl.northwestern.edu/netlogo/models/WolfSheepPredation NetLogo has a similar simulation which has more extensive controls and allows students to see how predation affects more than one population.

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
This simulation focuses on how this population is affected when factors change in the ecosystem (a field). Students should be encouraged to offer explanations for why the population changes or remains stable as the different factors are controlled. Students need to explain the relationship of the different factors to the carrying capacity of the ecosystem. The advantage of the simulation is that students can then see if the data supports their explanations.

Resource Quality

  • Alignment to the Dimensions of the NGSS: Population Explosion is an agile simulation which lends itself to three-dimensional learning. By using a computer simulation to modify factors that affect the size of a population, students learn about stability and change in a population over time. Teachers should be thoughtful about using its potential to help make sense of phenomena because it may be tempting for students to simply play with the simulation without much thought. Although allowing students to familiarize themselves with the tool at first may be wise, the simulation will be best used to support students as they make sense of how different factors affect populations.

  • Instructional Supports: This simulation has the potential to engage students in meaningful scenarios and to deepen their understanding of the practice, core idea, and cross-cutting concepts to which it aligns. The activity provides opportunities for students to express, clarify, analyze, and extend their thinking. Peer and teacher feedback opportunities may easily be incorporated as students work through the simulation. If teachers and students sign up through the “Innovative Technology in Science Inquiry” portal, then teachers may create specific assignments for their classes to use with the simulation which could then be used to differentiate instruction. Extension ideas are offered for students who engage in the simulation and would like to deepen their understanding of the concepts surrounding carrying capacity.

  • Monitoring Student Progress: Formative assessments are embedded within the provided student activities, the snapshot album allows teachers to see how students are progressing in their understanding, and the provided analysis at the end of the activity provides teachers with ways to gauge student understanding.

  • Quality of Technological Interactivity: Overall the technology works well. During testing, the simulation stalled and had to be reset. Using the control that varies the speed of the simulation may help students see more clearly what is happening over time, as students vary the different factors.