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9th, 10th, 11th, 12th, AP® / College


Science, Biology, English Language Arts, Mathematics

Resource Types

  • Activity - Classroom
  • Worksheets
  • Scientific Papers or Reports

Regional Focus

North America, United States, USA - West, Utah


Google Docs, PDF

Cougars and Trees in a Trophic Cascade

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  • In this activity, students analyze and interpret two graphs from a study that investigated the ecosystem effects of the displacement of cougars in Zion National Park.
  • Students are tasked with describing how changes in one population in an ecosystem can affect other populations through a trophic cascade. 
Teaching Tips


  • This resource is an excellent introduction to reading scientific papers and allows students to practice simplifying complex ideas and information.
  • The resource is available in Spanish and English, and includes educator materials, a student handout, and the original research paper.

Additional Prerequisites

  • Edits to the Google documents can be made by making a copy.
  • Students should have a strong understanding of reading and interpreting graphs and a general understanding of trophic levels and how they interact.
  • Once printed out, this resource does not require access to the internet.
  • There are specific standards listed for AP Biology, AP Environmental Science and IB courses that you can reference.


  • In more advanced classes, students can read the full research paper provided in the resource and analyze the methods, data analysis, and conclusions.
  • The educator materials include a guide for using the resource, background information, an explanation of how to interpret the graph, discussion questions, and a list of key terms, which can be used to assist students with less science or math backgrounds.
  • This lesson can also be used in math and statistics classes during lessons about standard error, correlation coefficients, and sampling and in social studies classes during lessons about the environmental impact of the tourism industry.
  • Similar resources include this video on trophic pyramids and this video on how trophic levels interact.
Scientist Notes
This resource contains materials and activities that would engage students to compute the trophic level, analyze other factors like tree size, age and specie-richness and also evaluate the human impacts on an ecosystem. This is recommended for teaching.

This resource addresses the listed standards. To fully meet standards, search for more related resources.

  • Mathematics
    • Statistics & Probability: Interpreting Categorical & Quantitative Data (9-12)
      • HSS.ID.A.4 Use the mean and standard deviation of a data set to fit it to a normal distribution and to estimate population percentages. Recognize that there are data sets for which such a procedure is not appropriate. Use calculators, spreadsheets, and tables to estimate areas under the normal curve.
  • Science
    • LS2: Ecosystems: Interactions, Energy, and Dynamics
      • 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.
      • HS-LS2-6. Evaluate 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.
      • HS-LS2-7. Design, evaluate, and refine a solution for reducing the impacts of human activities on the environment and biodiversity.
  • Related Resources


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