Food Chains and Food Webs

Students learn best when they can physically manipulate and visualize the complex relationships in ecosystems. Active learning turns abstract energy flow into a tangible process, helping students see how every organism depends on others in real Irish habitats like hedgerows or bogs.

• 6th Year
• The Living World: Foundations of Biology
• 4 activities
• 30 min–50 min

Learning Objectives

1. Analyze the flow of energy through a specific Irish ecosystem's food web, identifying at least three trophic levels.
2. Create a visual representation of a local food web, accurately classifying organisms as producers, primary consumers, secondary consumers, tertiary consumers, and decomposers.
3. Predict and explain the cascading effects on an ecosystem if a keystone species, such as the Atlantic puffin or a specific pollinator, is removed.
4. Evaluate the essential role of decomposers, such as fungi and bacteria, in nutrient cycling and soil health within terrestrial and aquatic environments.
5. Compare the energy transfer efficiency between different trophic levels in a food web, calculating the approximate energy loss at each stage.

Concept Mapping

⏱ 35 min·Pairs

Card Sort: Local Food Web Build

Provide cards with local Irish species, arrows for energy flow, and labels for trophic levels. Students in pairs sort and connect cards into a food web on large paper, then label producers, consumers, and decomposers. Discuss as a class.

Prepare & details

Construct a food web for a local ecosystem, identifying producers, consumers, and decomposers.

Facilitation Tip: During the Card Sort, ask students to explain their connections aloud before finalizing the web, reinforcing peer learning and correcting mistakes in real time.

Setup: Tables with large paper, or wall space

Materials: Concept cards or sticky notes, Large paper, Markers, Example concept map

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

Concept Mapping

⏱ 45 min·Small Groups

Disruption Simulation: Species Removal

Groups construct a baseline food web with string linking species photos. Remove a key species like a hedgehog, then trace effects on connected organisms using colored markers. Predict population changes and share findings.

Prepare & details

Predict the consequences for an ecosystem if a key species in its food web were removed.

Facilitation Tip: In the Disruption Simulation, have students write down their predictions before removing any species, then compare these to the actual ripple effects they observe.

Setup: Tables with large paper, or wall space

Materials: Concept cards or sticky notes, Large paper, Markers, Example concept map

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

Concept Mapping

⏱ 50 min·Small Groups

Decomposer Demo: Nutrient Cycle Jar

Layer soil, leaves, and worms in clear jars. Students observe weekly, recording decomposition and plant regrowth with added water. Compare jars with and without decomposers to note nutrient recycling.

Prepare & details

Explain the critical role of decomposers in recycling nutrients within an ecosystem.

Facilitation Tip: For the Decomposer Demo, remind students to photograph the jar daily and note any changes in color or texture to track decomposition progress.

Setup: Tables with large paper, or wall space

Materials: Concept cards or sticky notes, Large paper, Markers, Example concept map

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

Concept Mapping

⏱ 30 min·Pairs

Field Sketch: Schoolyard Web

Individuals sketch a simple food chain from school grounds, noting three levels plus decomposers. Pairs combine sketches into a class web on butcher paper, highlighting overlaps.

Prepare & details

Construct a food web for a local ecosystem, identifying producers, consumers, and decomposers.

Facilitation Tip: When guiding the Field Sketch, provide clipboards and ask students to label producers, consumers, and decomposers directly on their drawings for clarity.

Setup: Tables with large paper, or wall space

Materials: Concept cards or sticky notes, Large paper, Markers, Example concept map

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

Teaching This Topic

Start with a brief whole-class discussion using local examples like a hedgerow or coastal dune to ground the concept in familiar ecosystems. Avoid starting with a lecture on trophic levels; instead, let students discover complexity through hands-on modeling. Research shows that students retain energy flow concepts better when they build models and test predictions rather than memorize terms.

What to Expect

By the end of these activities, students will confidently build accurate food webs, explain energy loss at each trophic level, and justify the critical role of decomposers. They will also predict ripple effects when species disappear, using clear evidence from their models and observations.

Watch Out for These Misconceptions

Common Misconception

During the Card Sort activity, watch for students who arrange organisms in rigid, linear chains without cross-connections.

What to Teach Instead

Have students pause after their first draft and ask peers to suggest missing links, such as a hedgehog that eats both slugs and berries, to highlight the branching nature of real food webs.

Common Misconception

During the Disruption Simulation, watch for students who believe energy increases as it moves up the food chain.

What to Teach Instead

Give each student 10 tokens to represent energy at the producer level, then have them pass only 1 token up each link while setting aside the rest as 'lost heat', making the 10 percent rule visible and concrete.

Common Misconception

During the Decomposer Demo, watch for students who dismiss decomposers as unimportant or unrelated to producers.

What to Teach Instead

Ask students to predict what will happen to the soil in their jar after a week and compare it to a control jar without decomposers, using observations to show how nutrient recycling sustains plant growth.

Assessment Ideas

Quick Check

After the Card Sort, collect each group's final food web and check for five correctly connected organisms, accurate producer identification, and clear top consumer labeling to assess their understanding of energy flow direction.

Discussion Prompt

During the Disruption Simulation, listen for students to name three specific organisms affected by the removal of a species like earthworms, such as badgers, robins, and oak trees, and explain the direct and indirect links they identified.

Exit Ticket

After the Decomposer Demo, have students write two sentences explaining how decomposers recycle nutrients and why this process is essential for maintaining healthy ecosystems over time, using evidence from their jar observations.

Extensions & Scaffolding

• Challenge students to create a food web for an ecosystem with invasive species, such as grey squirrels in Irish woodlands, and explain how these disrupt local webs.
• For students who struggle, provide pre-labeled organism cards with arrows already drawn to help them focus on relationships.
• Use the nutrient cycle jar to explore variables like temperature or moisture by setting up additional jars with different conditions for comparative analysis.

Key Vocabulary

Producer	An organism that produces its own food, usually through photosynthesis, forming the base of a food chain. Examples include plants and algae.
Consumer	An organism that obtains energy by feeding on other organisms. Consumers are classified as primary (herbivores), secondary (carnivores or omnivores), or tertiary.
Trophic Level	The position an organism occupies in a food chain or food web. Energy is transferred from one trophic level to the next.
Decomposer	Organisms, primarily bacteria and fungi, that break down dead organic matter and waste products, returning nutrients to the ecosystem.
Biotic Potential	The maximum reproductive capacity of an organism under ideal conditions, influencing population dynamics within a food web.