Lesson Plan


In this lesson, students will conduct a simulation to explore the effects predator-prey interactions on population size. Then, students will identify limiting factors and design an experiment on limiting factors and plant growth. Students will:

  • simulate and explain predator-prey interactions.

  • explain how limiting factors affect population dynamics.

  • differentiate between density-dependent limiting factors and density-independent limiting factors.

  • design an experiment on the effects of limiting factors on seedling growth.

Essential Questions


  • Carrying Capacity: The largest number of individuals in a population that an environment can support.

  • Exponential Growth: A population growth pattern in which individuals reproduce at a constant rate.

  • Logistic Growth: A population growth pattern in which the growth rate slows down or stops after a period of exponential growth.

  • Predator: An organism that kills and eats other organisms.

  • Prey: An organism that is killed and eaten by another organism.

  • Limiting Factors: Factors that regulate population growth.

  • Density-Dependent Limiting Factors: Limiting factors that depend on population size.

  • Density-Independent Limiting Factors: Limiting factors that affect all populations in similar ways, regardless of population size.


75–90 minutes/2 class periods

Prerequisite Skills

Prerequisite Skills haven't been entered into the lesson plan.


Related Unit and Lesson Plans

Related Materials & Resources

The possible inclusion of commercial websites below is not an implied endorsement of their products, which are not free, and are not required for this lesson plan.

Formative Assessment

  • View
    • Collect and check the Predator-Prey Interaction handout.

    • Assess whether students understand predator-prey interactions by discussing the analysis and conclusions to the simulation.

    • Orally assess whether students understand the categories of limiting factors during the whole-class graphic organizer activity.

    • Circulate around the room and discuss students’ investigation procedures, asking them to describe the limiting factor(s) in their experiments.

    • Collect students’ graphs from the Predator-Prey Interactions activity.

Suggested Instructional Supports

  • View
    Scaffolding, Active Engagement, Explicit Instruction

    Students will begin the lesson by conducting a simulation on predator-prey interactions and they will answer related questions on a handout. They will learn that predation is one type of limiting factor, and then work as a whole class to brainstorm other limiting factors on populations.


    Students will be hooked into this lesson with a hands-on simulation on predation.


    Students express their understanding by answering follow-up questions to the simulation and by designing their own lab experiment on limiting factors.


    Students reflect on the simulation by making a general conclusion about how predator and prey populations affect one another. They rethink types of limiting factors by classifying them as density-dependent or density-independent.


    Students express their understanding by making predictions about generations in the simulation, and by writing an experimental procedure to investigate limiting factors.


    Instruction can be tailored by modeling the activities in the lesson and guiding students in creating a graphic organizer on limiting factors. The lesson can be extended by having students design a simulation that includes another predator, and having students research the grey wolf population in the United States.


    The first part of the lesson is a hands-on, exploratory activity on predation, which is one type of limiting factor. Then, students determine other limiting factors on populations and extend their understanding of limiting factors by designing a related experiment.

Instructional Procedures

  • View

    Preparation: Cut index cards into large and small squares (see Materials list and S-B-2-2_ Predator-Prey Cards.docx); place them into baggies for each group.

    Part 1: Predator-Prey Simulation

    Begin by asking students to define predator and prey and give examples of predator-prey relationships from the food chains and food webs in Lesson 1. These concepts should be prior knowledge.

    Small-Group Activity: Predator-Prey Interactions

    Divide students into groups of three to four students and distribute the predator and prey cards (S-B-2-2_ Predator-Prey Cards.docx) and the Predator-Prey Interactions handout to each group (S-B-2-2_ Predator-Prey Interactions.docx). Read through the procedure with students and answer any questions they have. Have student groups complete the activity, recording their data in the Predator-Prey Data Table (S-B-2-2_ Predator-Prey Interactions.docx). Have students answer the analysis questions and write their conclusions, and then discuss their conclusions about the relationship between the sizes of predator and prey populations.

    Explain exponential growth in populations. Then, explain logistic growth and carrying capacity using the double-line graph students created. Reserve discussion of limiting factors for Part 2.

    Part 2: Limiting Factors

    Ask students to consider the Predator-Prey Simulation. Ask, “What stops the mouse population from growing bigger and bigger?” and “What stops the fox population from growing continuously?” Explain that predator-prey relationships are an example of a limiting factor, because they control the population size of both the predators and the prey.

    On the board, write “Population Size” in a circle. Draw several circles near the first circle, and write “Predation” in one of them. Guide students in determining other limiting factors for populations. Limiting factors include (but are not limited to): competition, parasitism, disease, natural disasters, drought, forest fires, and human disturbances. Have students copy the graphic organizer into their notes, and allow time for them to write down any examples they can think of for the limiting factors (e.g., weeds and crop plants competing for light, space, and nutrients in a vegetable garden). Have students share their ideas.

    Explain the difference between density-dependent and density-independent limiting factors. Have students label each of the limiting factors in their notes into one of these categories (“D.D.” and “D.I.”). Density-dependent limiting factors include competition, predation, parasitism, diseases and density-independent limiting factors include drought, natural disasters including forest fires, and human disturbances such as clear-cutting forests and hunting.

    Partner Activity: Designing an Experiment on Limiting Factors

    Have students design an investigation on how plant competition affects seedling growth. Have pairs of students begin by writing a hypothesis (e.g., “If seedlings have more space, they will grow faster than seedlings with less space.) Check hypotheses before students proceed with developing the investigation. Then, students write a materials list and step-by-step procedure to test the hypothesis. If possible, allow students to conduct the investigation over about two weeks to test the hypothesis. Discuss how limiting factors can affect plant growth.


    • For Part 1, assist students who may need opportunities for additional learning by modeling the first several steps of the Predator-Prey Simulation procedure and showing students how to record their data.

    • Challenge students performing above and beyond the standards by having them create a double-line graph of their data. Alternatively, have them create an alternate version of the simulation that includes wolves as fox predators.

    • Another extension for predator-prey interactions is having students complete the online activity Leopard Seals and Penguins: A Delicate Balance (see the Leopard Seals and Penguins: A Delicate Balance Web site in Related Resources).

    • For Part 2, assist students who may need opportunities for additional learning by guiding them in making a table on the limiting factors discussed in this lesson with the headings “Factor,” “Definition,” and “Example.”

    • Challenge students performing above and beyond the standards by having them research the limiting factors on the gray wolf population in the United States and the efforts that have been made by humans to reintroduce the gray wolf. Then have them write a persuasive essay for or against reintroducing gray wolves. (See Related Resources for more information.)

Related Instructional Videos

Note: Video playback may not work on all devices.
Instructional videos haven't been assigned to the lesson plan.
DRAFT 11/19/2010
Please wait...