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Ecosystems | Activity 2.3

Activity 2.3: Evidence-based Arguments About Biomass Patterns in Ecosystems (40 min)

Students use the results of the Meadow Simulation to recognize a consistent pattern in ecosystems: the biomass in the herbivore population is smaller than the producer biomass, and biomass in the carnivore population is always the smallest.

Materials You Provide

  • Pencils (1 per student)

Resources Provided


Prepare a computer and a projector to display the PPT and one copy of the worksheet for each student.


1. Discuss results of the Meadow Ecosystem investigation.

Ask students to take out their completed 2.2 Meadow Simulation Worksheet worksheet. Open 2.3 Biomass Patterns in Ecosystems PPT.

  • Use slide 2 to discuss the maximum biomass of foxes and rabbits that students observed in any trial of the investigation. Make sure that they recognize that many different initial settings lead to the same final outcomes (maximum biomass of foxes = 9 and maximum biomass of rabbits = 90).
  • Use slide 3 to discuss the maximum biomass of grasses that students observed in any trial of the investigation. Make sure that students recognize that the maximum grass biomass was observed when the rabbits died out, since there were no herbivores to eat the grass.


Remember that at this point in the Unit it is okay for students to have many unanswered questions and incorrect ideas. It is important that they are able to describe the biomass pyramid as a pattern in ecosystems, but they should not be expected to fully explain it at this point. Use the 2.3 Assessing the Evidence-Based Arguments Tool for Ecosystems to get a sense for where students are in their ability to identify the main pattern in this unit: the biomass pyramid.