Objective
Students will be able to describe the roles of producers, consumers, and decomposers in an ecosystem, construct a food chain showing the flow of energy, and explain what happens when one organism in the food chain is removed. Students will accurately build at least one complete food chain with 4 or more organisms.
Standards
- NGSS 5-LS2-1 — Develop a model to describe the movement of matter among plants, animals, decomposers, and the environment.
- NGSS 5-PS3-1 — Use models to describe that energy in animals' food was once energy from the sun.
Materials
- Ecosystem anchor chart (producers, consumers, decomposers)
- Organism picture cards (30 cards: 6 producers, 18 consumers at various trophic levels, 6 decomposers)
- Yarn or string (for food web activity)
- Food chain template strips (arrow-connected boxes)
- "Who Eats What? Food Chains and Food Webs" by Patricia Lauber
- Ecosystem disruption scenario cards (6 cards)
- Assessment worksheet
Warm-Up (5 minutes)
Display a picture of a sunny meadow with grass, a rabbit, and a hawk. Ask: "What is the rabbit eating? What eats the rabbit? Where does the grass get its energy?" Trace the energy pathway: sun provides energy to grass, grass is eaten by the rabbit, rabbit is eaten by the hawk. Introduce the term "food chain" — a pathway that shows how energy flows from one living thing to the next. Every food chain starts with energy from the sun.
Direct Instruction (12 minutes)
Build the ecosystem anchor chart with three key roles:
Producers — Organisms that make their own food using sunlight (photosynthesis). They are always at the bottom of the food chain. Examples: grass, trees, algae, flowers, seaweed.
Consumers — Organisms that eat other organisms for energy. Three types:
- Primary consumers (herbivores): eat producers. Examples: rabbit, deer, grasshopper.
- Secondary consumers (omnivores/carnivores): eat primary consumers. Examples: frog, snake, small bird.
- Tertiary consumers (top predators): eat secondary consumers. Examples: hawk, wolf, shark.
Decomposers — Organisms that break down dead matter and return nutrients to the soil. Examples: mushrooms, earthworms, bacteria. They connect to every level of the food chain.
Model building a complete food chain on the board: Sun -> grass -> grasshopper -> frog -> snake -> hawk. Draw arrows showing the direction of energy flow. Explain that the arrow means "is eaten by" or "energy flows to." Then ask: "What happens if we remove the frogs from this chain?" Guide students to see that grasshopper populations would increase (nothing eating them) and snake populations would decrease (lost their food source). This is called an ecosystem disruption.
Read a short section from "Who Eats What?" to reinforce concepts with real-world examples.
Guided Practice (10 minutes)
Distribute organism picture cards to each table group (5–6 cards per group from the same ecosystem). Groups arrange their cards into a food chain, placing the producer first and adding arrows between each organism. Each group shares their food chain with the class and explains each connection. Example groups:
- Ocean: Seaweed -> sea urchin -> sea otter -> orca
- Forest: Oak tree -> squirrel -> fox -> mountain lion
- Pond: Algae -> tadpole -> dragonfly -> bass -> heron
After sharing, connect the food chains into a food web using yarn. Stand in a circle, each student holding an organism card. When two organisms are connected (one eats the other), stretch a piece of yarn between them. By the end, the yarn shows a complex web. Then simulate a disruption: have one student (an organism) drop their yarn. Ask: "How many other organisms were affected?" Students see that removing one species affects many others.
Independent Practice (10 minutes)
Students complete the assessment worksheet with three tasks:
- Build a food chain: Given 5 organisms and the sun, arrange them in the correct food chain order and draw arrows showing energy flow.
- Label the roles: For each organism in the food chain, write whether it is a producer, primary consumer, secondary consumer, tertiary consumer, or decomposer.
- Predict a disruption: Read a scenario card (e.g., "A disease kills most of the rabbits in a grassland ecosystem") and write 2–3 sentences explaining what would happen to the other organisms in the food chain.
Assessment
- Formative: During the group food chain building, check that arrows point in the correct direction (from prey to predator, showing energy flow) and that producers are at the base.
- Summative: Collect worksheets. Score: correct food chain order (2 points), all roles correctly labeled (2 points), disruption prediction is logical and shows understanding of interconnectedness (2 points). Total: 6 points.
Differentiation
- Struggling learners: Provide a food chain with 3 organisms instead of 5. Offer a word bank for roles (producer, consumer, decomposer). Use a completed food chain as a model to reference. Work in a teacher-led small group for the disruption prediction.
- ELL students: Pre-teach vocabulary with picture cards: producer, consumer, decomposer, energy, food chain, ecosystem. Allow drawings instead of written sentences for the disruption prediction. Provide sentence frames: "If the _____ disappeared, then the _____ would _____ because _____."
- Advanced learners: Ask them to build a food web (not just a chain) with at least 8 organisms. Introduce the concept of trophic levels and energy pyramids (only 10% of energy transfers to the next level). Research and present on a real-world ecosystem disruption (e.g., wolves reintroduced to Yellowstone).
- Students with IEPs: Provide pre-cut organism cards that students arrange and glue onto the template instead of drawing. Offer a step-by-step visual guide for building the food chain. Allow verbal responses for the disruption prediction. Reduce to identifying 3 roles instead of all 5.
Closure (5 minutes)
Return to the warm-up image of the meadow. Ask: "Can you now explain the complete food chain in this picture, including what would happen if we removed one organism?" Call on volunteers to trace the chain and predict disruptions. Then pose a higher-level question: "Why do food chains always start with the sun?" (Because the sun is the original source of energy for all life.) Close by having each student write one thing they learned on a sticky note and place it on the "exit door." Preview tomorrow's lesson on food webs and how multiple food chains overlap in an ecosystem.