Science · Grade 7

Active learning ideas

Energy Flow: Food Chains and Food Webs

Active learning helps students grasp energy flow because energy transfer is invisible and abstract. Moving, touching, and building models makes the 10 percent rule concrete and the complexity of webs visible. Working in teams also lets students argue about connections and corrections in real time, which strengthens understanding better than listening alone.

• Ontario Curriculum Expectations
• MS-LS2-3

• 25–40 min
• Pairs → Whole Class
• 4 activities

Activity 01

• Concept Mapping
• 35 min · Small Groups

Card Sort: Building Food Webs

Provide cards with local organisms, arrows for energy flow, and habitat labels. In small groups, students first arrange into simple food chains, then connect them into a food web, labeling trophic levels. Discuss interconnections and predict effects of species removal.

Analyze the impact of removing a keystone species from a food web.

Facilitation Tip

During Card Sort: Building Food Webs, arrange desks in small groups and place one set of organism cards and arrows at each table so students physically move pieces to test multiple configurations.

What to look for

Provide students with a list of organisms found in a specific habitat (e.g., a temperate forest). Ask them to draw a simple food chain with at least three trophic levels and identify the producer, primary consumer, and secondary consumer. Then, ask them to write one sentence explaining what would happen if the producer disappeared.

• Understand
• Analyze
• Create
• Self-Awareness
• Self-Management

Activity 02

• Concept Mapping
• 25 min · Whole Class

Yarn Web Simulation

Students stand in a circle holding cards for organisms. Toss yarn balls to represent feeding links while naming trophic roles. Remove a 'keystone' student and observe web collapse, then reconstruct and analyze stability.

Differentiate between a food chain and a food web using specific examples.

Facilitation Tip

During Yarn Web Simulation, have one student from each group hold the center yarn and rotate partners to add strands, forcing repeated connections and overlaps.

What to look for

Display an image of a complex food web on the board. Ask students to identify one omnivore and one tertiary consumer. Then, pose a hypothetical: 'If the population of the main herbivore in this web decreased significantly, what are two other populations that would likely be affected and why?'

• Understand
• Analyze
• Create
• Self-Awareness
• Self-Management

Activity 03

• Concept Mapping
• 40 min · Small Groups

Energy Pyramid Layers

Groups stack foam blocks or draw pyramids representing trophic levels, adding organism cutouts and calculating 10% energy rule with sample data. Compare pyramids before and after removing a producer.

Construct a complex food web for a given habitat, identifying trophic levels.

Facilitation Tip

During Energy Pyramid Layers, assign color-coded blocks to groups so they can stack and compare sizes before writing energy values on sticky notes.

What to look for

Present a scenario: 'Imagine the sea otter, a keystone species in kelp forests, is removed from the ecosystem. Discuss in small groups: What other organisms rely on kelp? What might happen to the sea urchin population? How could this impact the entire kelp forest ecosystem?' Facilitate a brief whole-class share-out of key ideas.

• Understand
• Analyze
• Create
• Self-Awareness
• Self-Management

Activity 04

• Concept Mapping
• 30 min · Pairs

Digital Food Web Builder

Use free online tools like Food Web Designer. Individually or in pairs, input a habitat's species, link them, and run removal scenarios to graph population changes.

Analyze the impact of removing a keystone species from a food web.

Facilitation Tip

During Digital Food Web Builder, circulate with a checklist of key terms students must include in their final web to ensure rigor.

What to look for

Provide students with a list of organisms found in a specific habitat (e.g., a temperate forest). Ask them to draw a simple food chain with at least three trophic levels and identify the producer, primary consumer, and secondary consumer. Then, ask them to write one sentence explaining what would happen if the producer disappeared.

• Understand
• Analyze
• Create
• Self-Awareness
• Self-Management

A few notes on teaching this unit

Start with simple food chains to build confidence, then shift to webs as soon as students can name producers and consumers. Avoid starting with pyramids; many students confuse energy loss with population numbers until they see real webs first. Research shows that students who build webs with yarn remember trophic relationships 30 percent better than those who only diagram, likely because the physical tension in the strings mimics energy transfer constraints.

Students should be able to trace energy paths through at least three trophic levels, quantify energy loss between levels, and explain how decomposers close the loop. They should describe webs as dynamic networks with shared links rather than separate chains and identify keystone roles that stabilize or destabilize energy flow.

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Watch Out for These Misconceptions

• During Card Sort: Building Food Webs, watch for students who arrange organisms in equal rows or stacks, assuming energy stays constant.

  Prompt them to measure energy loss by assigning each arrow a label that drops the energy value by 90 percent, forcing them to shrink block sizes or reduce candy amounts as energy moves up levels.

• During Yarn Web Simulation, watch for students who treat each yarn strand as a separate chain rather than part of a shared network.

  Ask each group to tug one strand and notice which other strings jiggle, explicitly linking shared consumers like omnivores to multiple energy sources.

• During Energy Pyramid Layers, watch for students who exclude decomposers from the cycle or place them at the top of the pyramid.

  Have them physically move decomposer blocks from the side into the base of the pyramid and trace arrows back to producers, clarifying nutrient recycling.

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Methods used in this brief

• Concept Mapping