Energy Flow in Ecosystems

Active learning works for energy flow because students need to manipulate the abstract concept of energy transfer to see its real effects. Building pyramids and simulating transfers make the ten percent rule tangible, while discussions about disruptions help students connect classroom ideas to ecosystems they can picture in Ontario.

• Grade 9
• Science
• 4 activities
• 20 min–50 min

Learning Objectives

1. Calculate the percentage of energy transferred between successive trophic levels in a given food web.
2. Construct an energy pyramid for a specific Ontario ecosystem, identifying sources of energy loss at each level.
3. Analyze the impact of removing a keystone species on the overall energy flow and stability of an ecosystem.
4. Explain the ecological reasons behind the ten percent energy transfer rule between trophic levels.

Experiential Learning

⏱ 30 min·Pairs

Pairs: Energy Pyramid Construction

Provide students with printed images of local producers, herbivores, carnivores, and apex predators. Pairs stack them into a pyramid, labeling energy at each level starting with 100% at producers and calculating ten percent transfers. Discuss losses and redraw if imbalances occur.

Prepare & details

Justify why only ten percent of energy is typically passed between trophic levels in a food web.

Facilitation Tip: During Energy Pyramid Construction, circulate to ensure pairs use consistent units when labeling energy at each level so they see the cumulative loss.

Setup: Varies; may include outdoor space, lab, or community setting

Materials: Experience setup materials, Reflection journal with prompts, Observation worksheet, Connection-to-content framework

• Apply
• Analyze
• Evaluate
• Self-Awareness
• Self-Management
• Social Awareness

Experiential Learning

⏱ 45 min·Small Groups

Small Groups: Ball Drop Energy Transfer

Give each group 100 small balls as incoming energy to producers. Groups pass ten balls to herbivores, then one to carnivores, simulating losses by 'eating' or dropping extras. Record final energy at each level and graph results.

Prepare & details

Construct an energy pyramid for a local ecosystem, identifying potential energy losses.

Facilitation Tip: In Ball Drop Energy Transfer, remind small groups to count drops carefully and record losses immediately to avoid confusion during debates.

Setup: Varies; may include outdoor space, lab, or community setting

Materials: Experience setup materials, Reflection journal with prompts, Observation worksheet, Connection-to-content framework

• Apply
• Analyze
• Evaluate
• Self-Awareness
• Self-Management
• Social Awareness

Experiential Learning

⏱ 50 min·Whole Class

Whole Class: Keystone Disruption Simulation

Assign roles in a food web projected on the board. Remove a keystone species volunteer and have chains react by adjusting energy flows with string connections. Class votes on ecosystem stability before and after.

Prepare & details

Analyze how the removal of a keystone species impacts energy flow within its ecosystem.

Facilitation Tip: For Keystone Disruption Simulation, give clear roles so every student participates in tracking energy shifts and recording observations.

Setup: Varies; may include outdoor space, lab, or community setting

Materials: Experience setup materials, Reflection journal with prompts, Observation worksheet, Connection-to-content framework

• Apply
• Analyze
• Evaluate
• Self-Awareness
• Self-Management
• Social Awareness

Experiential Learning

⏱ 20 min·Individual

Individual: Local Ecosystem Pyramid

Students research a Ontario wetland or forest ecosystem online or from provided data sheets. They sketch and label an energy pyramid, noting ten percent transfers and one potential keystone species.

Prepare & details

Justify why only ten percent of energy is typically passed between trophic levels in a food web.

Facilitation Tip: When students work on the Local Ecosystem Pyramid, provide Ontario-specific producer examples to ground the abstract pyramid in familiar ecosystems.

Setup: Varies; may include outdoor space, lab, or community setting

Materials: Experience setup materials, Reflection journal with prompts, Observation worksheet, Connection-to-content framework

• Apply
• Analyze
• Evaluate
• Self-Awareness
• Self-Management
• Social Awareness

Teaching This Topic

Teachers often start with a demonstration of energy transfer using household items before moving to simulations. It helps to emphasize that the ten percent rule is an estimate, not a law, and that real ecosystems vary. Avoid over-simplifying by letting students debate why energy loss differs by organism, using local examples to keep discussions concrete.

What to Expect

Students will explain energy loss between trophic levels and justify the ten percent rule using data they collect themselves. They will analyze how energy availability changes when a keystone species is removed and apply these ideas to local ecosystems like the Great Lakes food web.

Watch Out for These Misconceptions

Common Misconception

During Energy Pyramid Construction, watch for students who describe energy as cycling rather than flowing one way.

What to Teach Instead

Have students label arrows showing direction of energy flow and ask them to explain why energy doesn’t return to the sun or producers.

Common Misconception

During Ball Drop Energy Transfer, watch for students who assume all groups will lose the same amount of energy.

What to Teach Instead

Ask students to compare their energy loss data and discuss why different organisms might transfer energy with varying efficiency.

Common Misconception

During Keystone Disruption Simulation, watch for students who think energy loss is the same in all ecosystems.

What to Teach Instead

Have students adjust their simulation parameters to test different loss rates and compare outcomes before concluding that ten percent is an average.

Assessment Ideas

Quick Check

After Energy Pyramid Construction, ask students to calculate energy available to the third trophic level if producers have 1000 units and explain where energy was lost.

Discussion Prompt

After Keystone Disruption Simulation, pose a scenario about a local ecosystem disturbance and ask students to use their observations to predict energy shifts for secondary and tertiary consumers.

Exit Ticket

During Local Ecosystem Pyramid, have students draw a pyramid for a pond or forest, label three trophic levels, and write one sentence about a specific energy loss between producer and primary consumer.

Extensions & Scaffolding

• Challenge: Have students compare energy pyramids for two Ontario ecosystems (e.g., boreal forest vs. Great Lakes) and explain why one might show greater energy loss at the producer level.
• Scaffolding: Provide a partially filled pyramid template for students who struggle with calculations or labeling at first.
• Deeper exploration: Invite students to research how invasive species disrupt energy flow in Ontario ecosystems and present findings to the class.

Key Vocabulary

Trophic Level	The position an organism occupies in a food chain or food web, representing its feeding position relative to producers.
Energy Pyramid	A graphical representation showing the amount of energy available at each trophic level in an ecosystem, typically decreasing at higher levels.
Biomass	The total mass of organisms in a given area or volume, often used to represent the energy stored at a particular trophic level.
Keystone Species	A species that has a disproportionately large effect on its environment relative to its abundance, significantly influencing ecosystem structure and energy flow.
Respiration (Ecological)	The metabolic process by which organisms convert organic matter into energy, releasing heat and carbon dioxide, thus losing energy from a trophic level.