Science · 7th Grade

Active learning ideas

Food Webs and Energy Flow

Active learning works for this topic because students need to visualize how energy moves through ecosystems, not just memorize terms. By building models and testing disruptions, they see firsthand why energy limits food chain length and how small changes ripple through a web.

• Common Core State Standards
• MS-LS2-3

• 20–45 min
• Pairs → Whole Class
• 4 activities

Activity 01

• Inquiry Circle
• 45 min · Small Groups

Inquiry Circle: Build-a-Food-Web

Groups receive species cards with diet, habitat, and trophic level information for a specific ecosystem (grassland, coral reef, or deciduous forest). Students arrange the cards and draw arrows showing energy flow direction to construct a complete food web, then identify producers, primary and secondary consumers, and the most likely keystone species based on their web's structure.

Explain how energy flows through different trophic levels in a food web.

Facilitation Tip

During Build-a-Food-Web, circulate with a red pen to correct arrow directions in real time, reinforcing that arrows show energy flow toward the eater, not the eaten.

What to look for

Provide students with a list of 10-15 organisms from a specific ecosystem (e.g., a temperate forest). Ask them to draw arrows showing energy flow and label at least four trophic levels. Then, ask: 'What would happen to the insect population if the bird population decreased by half?'

• Analyze
• Evaluate
• Create
• Self-Management
• Self-Awareness

Activity 02

• Think-Pair-Share
• 20 min · Pairs

Think-Pair-Share: The 10% Energy Rule

Present a specific food chain and ask students to calculate the energy available at each trophic level if 1,000 calories are fixed by producers. Students work individually, compare with a partner, and discuss why top predators have large territories and small populations compared to the prey species below them.

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

Facilitation Tip

In the 10% Energy Rule activity, have students physically count and move paper money to make the loss of energy tangible and memorable.

What to look for

Present a scenario: 'A disease drastically reduces the population of rabbits in a grassland ecosystem. What are three potential consequences for other organisms in the food web, and why?' Facilitate a class discussion where students justify their predictions based on energy flow and trophic relationships.

• Understand
• Apply
• Analyze
• Self-Awareness
• Relationship Skills

Activity 03

• Stations Rotation
• 40 min · Small Groups

Stations Rotation: Disrupting the Web

At three stations, students encounter a scenario where a species has been removed or dramatically reduced: overhunting of a predator, disease wiping out a primary consumer, invasive plant crowding out native producers. At each station, groups trace the ripple effects through a provided food web and predict which species increase and which decrease.

Predict the consequences of a disruption to the energy flow in an ecosystem.

Facilitation Tip

At Disrupting the Web stations, provide a timer so groups rotate quickly and stay focused on the impact of each disruption within the allotted time.

What to look for

On an index card, have students define 'keystone species' in their own words and provide one example. Then, ask them to explain how removing this species could impact at least two other organisms in its food web.

• Remember
• Understand
• Apply
• Analyze
• Self-Management
• Relationship Skills

Activity 04

• Gallery Walk
• 35 min · Small Groups

Gallery Walk: Trophic Cascade Case Studies

Post four documented trophic cascade examples around the room (wolves in Yellowstone, sea otters and sea urchins, sharks in Atlantic estuaries, elephants in African savannas). Groups rotate and annotate each case with the mechanism of the cascade and the unexpected species it affected, then the class compares patterns across all four cases.

Explain how energy flows through different trophic levels in a food web.

Facilitation Tip

For the Gallery Walk, assign each case study a specific question to answer, such as ‘How did the wolf’s return change energy flow in Yellowstone?’ to guide analysis.

What to look for

Provide students with a list of 10-15 organisms from a specific ecosystem (e.g., a temperate forest). Ask them to draw arrows showing energy flow and label at least four trophic levels. Then, ask: 'What would happen to the insect population if the bird population decreased by half?'

• Understand
• Apply
• Analyze
• Create
• Relationship Skills
• Social Awareness

A few notes on teaching this unit

Teachers approach this topic by treating it as a system, not a list of terms. Start with concrete examples students know, like a backyard food web, then generalize rules. Avoid overloading students with vocabulary upfront; let them discover the 10% rule through data. Research shows students retain these concepts better when they create, test, and revise models than when they passively receive information.

Successful learning looks like students correctly drawing energy arrows from prey to predator, explaining why only 10% of energy transfers between trophic levels, and predicting ecosystem changes when key species are removed. Their models should reflect real-world relationships and energy constraints.

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Watch Out for These Misconceptions

• During Build-a-Food-Web, watch for students who draw arrows pointing from predator to prey, indicating what eats what rather than the direction of energy flow.

  Pause the activity and ask students to trace the path of energy with their fingers, starting with grass and moving to the grasshopper. Reinforce: arrows go from the organism being eaten to the organism that eats it.

• During the 10% Energy Rule activity, watch for students who assume energy is recycled like matter because both are essential for life.

  Ask students to set aside 90% of their paper money in a ‘heat bucket’ after each transfer and explain why that energy is lost. Emphasize that energy flows in one direction and is not reused.

• During Disrupting the Web, watch for students who believe removing a top predator benefits prey by reducing predation.

  Point to the station’s graph showing prey population spikes followed by crashes. Ask students to explain why the initial spike leads to overgrazing and habitat degradation.

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Methods used in this brief

• Inquiry Circle
• Think-Pair-Share
• Stations Rotation
• Gallery Walk