1. Engage

Anchoring Phenomenon: Have you ever noticed that in any ecosystem—whether a forest, ocean, or grassland—there are always many more plants than herbivores, and even fewer apex predators (like lions, eagles, or sharks)? Why doesn’t an ecosystem have just as many predators as it does plants?

Discussion Questions:

  1. Where do the plants get their energy?
  2. What happens to the energy when a herbivore eats a plant?
  3. Do you think a predator gets 100% of the energy from the sun that the plant originally captured? Why or why not?

2. Explore

In this activity, you will use the Trophic Energy Pyramid Model simulation to trace how energy flows through an ecosystem.

Materials:

Estimated Time: 45 minutes

Instructions:

  1. Open the Trophic Energy Pyramid Model simulation.
  2. The model shows four trophic levels: Primary Producers, Primary Consumers, Secondary Consumers, and Tertiary Consumers.
  3. In the control panel, locate the Mathematical Inputs. You will see two sliders:
    • Producer Energy (J): The total amount of energy captured by the Primary Producers from the sun.
    • Efficiency Rate (%): The percentage of energy that is successfully transferred from one trophic level to the next.
  4. Set the Producer Energy to 10,000 J and the Efficiency Rate to 10%.
  5. Look at the Data Table and record your observations. Then, change the Efficiency Rate to 20% and record the new values.

Data Collection: Fill out the table below based on the simulation outputs.

Trophic Level Energy Available (10% Efficiency) (J) Energy Available (20% Efficiency) (J) Energy Lost to Heat/Waste (10% Efficiency) (J)
Primary Producers 10,000 10,000 _____
Primary Consumers _____ _____ _____
Secondary Consumers _____ _____ _____
Tertiary Consumers _____ _____ _____

3. Explain

Review your data table and the visual pyramid model to answer the following questions.

  1. Energy Loss: Compare the energy available at the Primary Producer level to the Energy Available at the Tertiary Consumer level. Where did the “lost” energy go? Use evidence from the “Energy Lost to Heat/Waste” column to support your answer. _____

  2. Mathematical Modeling: If the efficiency is 10%, what mathematical operation are you doing to find the energy of the next trophic level? Write a simple equation for $E_{next}$ given $E_{current}$ and Efficiency $r$ (as a decimal). _____

  3. Total Accounted For: Look at the “Total Accounted For” column in the simulation. For any trophic level, does the (Energy Available + Energy Lost) equal the Energy Available from the previous level? What law of physics does this demonstrate? _____

4. Elaborate

Now, imagine an ecosystem where the primary producers are devastated by a drought, reducing their total energy to 2,000 J.

  1. Set the Producer Energy slider to 2,000 J and leave the Efficiency at 10%.
  2. How much energy is left for the Tertiary Consumers? _____

Your Deliverable: Write a short paragraph explaining the anchoring phenomenon: why are there generally so few apex predators in an ecosystem? Support your claim using the mathematical evidence of energy transfer and loss you gathered from the simulation.

5. Evaluate (Teacher Notes)

Alignment to NGSS:

Evidence Statements Addressed:

Expected Deliverable Outcome: Students should explain that because only a fraction (e.g., 10%) of energy is transferred to each subsequent trophic level, there is significantly less energy available at the top of the pyramid. Therefore, an ecosystem can only support a small population of apex predators compared to the massive biomass of primary producers needed to sustain them.

Extensions: