Exploring Food Chains

Curriculum Area: Environmental Science (9th Grade)

Standards Alignment: NGSS (Next Generation Science Standards)

• HS-LS2-1: Use mathematical and/or computational representations to support explanations of factors that affect carrying capacity of ecosystems.
• HS-LS2-2: Construct an explanation of interactions among organisms in different ecosystems.
• HS-LS2-4: Use a model to illustrate the roles of photosynthesis and cellular respiration in the food web.

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Lesson Objectives

By the end of this 80-minute lesson, students will be able to:

1. Define food chains, food webs, and trophic levels in an ecosystem.
2. Differentiate between producers, consumers, and decomposers.
3. Create and analyze their own food web using local ecosystem examples.
4. Understand the flow of energy through trophic levels, including the concept of the 10% energy rule.
5. Work collaboratively to solve challenges related to disrupted food webs.

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Materials Needed

• Projector and computer for teacher presentation
• 2 sets of Food Web Role Cards (pre-made cards, roles like "Grass," "Rabbit," "Hawk," etc.)
• Large poster paper (one for each group)
• Markers, colored pencils, and sticky notes
• 72 Energy Tokens (small slips of paper or poker chips)
• Handouts with guided notes on food chains, food webs, and the 10% rule
• A printed food web of a local ecosystem (e.g., a forest or wetland in your state)

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Detailed Lesson Breakdown

1. Engage (10 Minutes)

• "Energy Journey" Icebreaker Demonstration

  • Choose 6 volunteers and give each a card with a role (e.g., "Sun," "Grass," "Rabbit," "Snake," "Hawk") to represent a simple food chain.

  • Hand 100 "Energy Tokens" to the "Sun." Prompt each student to transfer 10% of their energy to the next organism in the chain.

  • Pause and ask the class: “What happens to the rest of the energy?” (Answer: Lost as heat or used in life processes.)

  • Wrap up by explaining: "This is why ecosystems have fewer top predators — there’s less energy available as you move up trophic levels."

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2. Explain (15 Minutes)

• Direct Teaching with Visual Aids

  • Use a projector to present key terms: food chain, food web, trophic levels, producers, consumers, decomposers. Provide age-specific examples relevant to the students’ environment.
  • Illustrate the 10% energy rule using simple diagrams.
  • Discuss the differences between linear food chains and interconnected food webs.
  • Introduce the concept of ecosystem disruption (e.g., what happens if a species is removed).

  Teacher Pro Tip: Use humor to engage students! For example: “Imagine this—if we removed all the rabbits, hawks won’t be flying to Burger King for lunch.”

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3. Explore (30 Minutes)

• Collaborative Activity: Build Your Own Food Web

  • Divide students into groups of 6. Assign each group one of the following ecosystems (urban, forest, desert, wetland, etc.).
  • Provide each group with role cards (e.g., insects, plants, carnivores, decomposers) that fit their ecosystem and instructions to:
    • Create a food web on a large poster.
    • Use arrows to show energy flow.
    • Label each organism as a producer, primary consumer, secondary consumer, tertiary consumer, or decomposer.

  Energy Distribution Mini-Challenge:

  • Once the food web is complete, provide each group with 100 "Energy Tokens" to allocate through their web following the 10% energy rule.
  • Ask each group to explain which trophic level contains the most energy and why.

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4. Evaluate (15 Minutes)

• Peer Presentations & Class Discussion

  • Each group will hang their food web up and present it to the class.

  • As students present, encourage peers to ask questions like:

    • “What would happen if the [primary consumer] disappeared?”
    • “Can you explain how energy moves to the top predator?”

  • After presentations, lead a discussion using scenario-based questions:

    • "What happens if a pesticide kills off all the insects in an urban ecosystem?"
    • "If we reduced the number of plants, would it impact top predators like hawks? How?"

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5. Extend (10 Minutes)

• Individual Reflection & Creative Task
  • Have students write a quick journal entry in response to this question:
    • Imagine we added a species like wolves to your group's ecosystem. How would this affect your food web?
  • Allow creative students to draw another version of their food web with this new species included.

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Assessment Strategy

1. Formative Assessment: Guided questions during group work and presentations to check for understanding.
2. Summative Assessment: Collect posters and journals. Evaluate them based on:
   • Accuracy of food web components.
   • Clear explanation of energy flow and trophic levels.
   • Thoughtfulness of reflection or creative extension.

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Differentiation Strategies

• For visual learners, incorporate colorful diagrams and charts.
• For auditory learners, encourage class discussions and Q&A sessions.
• For kinesthetic learners, include hands-on activities like distributing tokens and physically building food webs.
• For advanced students, pose additional "What if?" scenarios (e.g., invasive species introduction) for them to analyze.
• For students needing extra support, provide pre-filled diagrams and definitions to reference during group activities.

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Homework/Additional Resources

• Assign students to research a real-life ecosystem and create a digital food chain using illustrations they either draw or find online.
• Have students track their own "personal food web" by listing everything they eat in a day and identifying its role in their diet (e.g., producer, primary consumer).

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Teacher Reflection After Lesson: After the class, consider evaluating how well students engaged with the collaborative activity. Did they actively participate? Were they able to transfer theoretical concepts into practical designs? Use this reflection to inform how you approach future lessons on ecosystems!