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Ecosystems | Activity 3.5

Activity 3.5: Explaining Patterns in Ecosystems (30 min)

Students use the Explanations Tool for Ecosystems to explain the biomass pyramid. They provide evidence at multiple scales for the Three Questions and then combine these ideas into one explanation for the pattern.

Materials You Provide

Resources Provided


Print one copy of the 3.5 Explanations Tool for Ecosystems for each student. Retrieve students’ completed 2.3 Evidence-Based Arguments Tool for Ecosystems.


1. Introduce the activity.

Tell students that at this point in the unit they should have evidence to support an explanation for the pattern in the biomass pyramid. The Explanations Tool in this activity will help them record their ideas about the Three Questions and combine these ideas into a scientific explanation.

  • Pass out students 2.3 Evidence-Based Arguments Tool for Ecosystems. Have them read their explanations from earlier. At that point, they would have been able to identify the pattern in the biomass pyramid, but they would not have explanations for why it happens.
  • Ask the for ideas about what additional evidence they have for why this might be happening. Encourage them to consider what they learned in the carbon dice game, and to consider evidence from multiple spatial scales: the atomic-molecular, the cellular, and the macroscopic.


Use 3.5 Grading the Explanations Tool for Ecosystems to get a sense of students’ explanations for the biomass pyramid. At this point, students should have well-developed explanations for the pattern they see. Look for the range of ideas in the class and consider what may need more emphasis to help the students develop more sophisticated explanations.