Food Chains and Food Webs

Active learning works for this topic because students need to see the complexity of energy flow and relationships in ecosystems firsthand. Building and testing models lets them experience how disruptions ripple through systems, turning abstract concepts into concrete understanding.

• 6th Grade
• Science
• 3 activities
• 20 min–35 min

Learning Objectives

1. Construct a food web diagram for a specific habitat, accurately representing producer, consumer, and decomposer relationships.
2. Explain the flow of energy through a food web, tracing it from producers to various trophic levels.
3. Predict the cascading effects on an ecosystem when a producer or consumer population changes significantly.
4. Compare and contrast the structure of different food webs found in distinct biomes (e.g., desert vs. forest).
5. Analyze the impact of removing a top predator on the populations of organisms at lower trophic levels.

Inquiry Circle

⏱ 35 min·Small Groups

Collaborative Model: Build a Local Food Web

Provide groups with species cards for a local ecosystem (e.g., a freshwater pond or tallgrass prairie). Students draw arrows connecting organisms based on feeding relationships, then compare their webs to other groups' versions. The class discusses where their webs agree and disagree, and why the same ecosystem can produce different valid models.

Prepare & details

Construct a food web for a local ecosystem.

Facilitation Tip: During the Collaborative Model activity, assign each group a specific organism and its energy source to ensure all roles are represented in the final web.

Setup: Groups at tables with access to source materials

Materials: Source material collection, Inquiry cycle worksheet, Question generation protocol, Findings presentation template

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

Simulation Game

⏱ 30 min·Small Groups

Simulation Game: Predator Removal Experiment

Using a physical web model with yarn or string connecting organism cards, remove a top predator species and have students physically trace which connections are now disrupted. Groups predict the population effects at each level, then compare their predictions to a documented real-world trophic cascade like the wolf reintroduction at Yellowstone.

Prepare & details

Predict what happens to an ecosystem when a top predator is removed.

Facilitation Tip: For the Predator Removal Experiment simulation, have students record population data in a shared table so the class can analyze trends together.

Setup: Flexible space for group stations

Materials: Role cards with goals/resources, Game currency or tokens, Round tracker

• Apply
• Analyze
• Evaluate
• Create
• Social Awareness
• Decision-Making

Think-Pair-Share

⏱ 20 min·Pairs

Think-Pair-Share: Producer Collapse Scenario

Present a scenario: a drought reduces the grassland producer population by 70%. Pairs work through the food web to predict population changes at each trophic level, writing their reasoning before sharing with the class. The discussion highlights that effects are not always predictable and can travel in both directions through the web.

Prepare & details

Analyze the impact of a decline in producer populations on an entire food web.

Facilitation Tip: In the Think-Pair-Share Producer Collapse activity, set a timer for 2 minutes of individual thinking to prevent students from jumping straight to the first idea they share with a partner.

Setup: Standard classroom seating; students turn to a neighbor

Materials: Discussion prompt (projected or printed), Optional: recording sheet for pairs

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

Teaching This Topic

Teach this topic by starting with familiar examples students can relate to, like backyard food webs, before moving to more complex systems. Use analogies they understand, such as money flow in a family budget, to explain energy transfer. Avoid overwhelming them with too many organisms at once; focus on depth over breadth to build strong foundational understanding.

What to Expect

Successful learning looks like students accurately representing energy transfer as one-way and limited, explaining how disruptions in one part of a food web affect others, and using evidence from models to support their reasoning. They should move from simple chains to recognizing the interconnectedness of food webs.

Watch Out for These Misconceptions

Common Misconception

During the Collaborative Model activity, watch for students who assume energy is recycled in the food web and reused exactly as it was in the previous organism.

What to Teach Instead

Use the passing chips model as a warm-up before the activity: have students pass 100 chips between groups, removing 90% each time to show energy loss and one-way flow, then connect this to the food web they build.

Common Misconception

During the Collaborative Model activity, watch for students who treat the food chain as a straight line with no branching or multiple connections.

What to Teach Instead

After building the initial web, have students count the number of incoming and outgoing arrows for each organism and highlight the organism with the most connections to emphasize the complexity of real food webs.

Common Misconception

During the Predator Removal Experiment simulation, watch for students who assume removing a predator will always benefit the prey population and the ecosystem overall.

What to Teach Instead

Have students revisit the Yellowstone wolf case study after the simulation, asking them to compare their initial predictions with the real outcomes and explain why their assumptions were incomplete.

Assessment Ideas

Exit Ticket

After the Collaborative Model activity, provide students with a list of 5-7 organisms from a local park or forest. Ask them to draw a simple food web connecting these organisms, label at least two trophic levels, and write one sentence predicting what might happen if the population of the top predator in their web decreased.

Quick Check

During the Think-Pair-Share Producer Collapse activity, display an image of a simple food chain (e.g., grass -> rabbit -> fox). Ask students to write down the producer, primary consumer, and secondary consumer, then pose the question: 'What would happen to the fox population if a disease wiped out most of the rabbits?' Have students write a brief explanation and share with a partner.

Discussion Prompt

After the Predator Removal Experiment simulation, present a scenario: 'Imagine a pond ecosystem where the algae population suddenly crashes due to pollution. What are three different organisms that would likely be affected, and how?' Facilitate a class discussion where students share their predictions and justify them based on food web principles.

Extensions & Scaffolding

• Challenge a small group to research and present an example of a keystone species and its role in a real ecosystem.
• Scaffolding: Provide pre-labeled organism cards with trophic level hints for students struggling to start the food web model.
• Deeper exploration: Ask students to research how human activities, like overfishing or deforestation, disrupt food webs and present findings to the class.

Key Vocabulary

Producer	An organism, usually a plant or alga, that produces its own food through photosynthesis, forming the base of a food chain.
Consumer	An organism that obtains energy by feeding on other organisms; includes herbivores, carnivores, and omnivores.
Decomposer	An organism, such as bacteria or fungi, that breaks down dead organic matter, returning nutrients to the ecosystem.
Trophic Level	The position an organism occupies in a food chain or food web, indicating its source of energy.
Food Web	A complex network of interconnected food chains showing the feeding relationships between multiple organisms in an ecosystem.