Grade 7 · Science · 30 minutes
Unit 1 · Living Connections · Lesson 1 of 2
Matter Cycles, Energy Flows
Revise a food-web model to include decomposers and a system boundary.
Mr. S Teaches · Original starter mini-lesson · MS7-SCI-01Learning objective
Model at least two matter pathways and explain why energy and matter are not interchangeable.
Before you begin
- Identify producers and consumers.
Gather your materials
- Paper or notebook
- Pencil and the passage, model directions or data printed in this lesson
Language to know
- producer
- An organism that makes sugars using an energy source.
- decomposer
- An organism that breaks down dead material and wastes.
- system boundary
- An imaginary line defining what a model includes.
Understand the concept
Ecosystem account: In a meadow, grass takes up water and mineral nutrients and uses light in making sugars. Rabbits eat grass; hawks eat rabbits. Fungi and bacteria break down dead organisms and wastes, returning materials to soil and air. Matter can move repeatedly among organisms and nonliving surroundings. Energy enters largely as sunlight and is transferred, with much ultimately dispersed as thermal energy. Energy does not circulate back from the soil to the Sun in the way nutrients cycle.
Teach it step by step
- Read the account and underline matter movements separately from energy transfers.
- Draw a meadow boundary with grass, rabbits, hawks, decomposers, soil and air inside.
- Add labeled matter arrows, including dead material to decomposers and nutrients back toward plants.
- Add a different style of energy arrow entering as sunlight and leaving as thermal energy; explain a difference between the arrow systems.
Make the thinking visible
Worked example or model response
Grass → rabbit → dead material → decomposer → soil nutrients → grass is a simplified matter pathway. Sunlight → grass → rabbit → surroundings shows energy transfer. Adding “Sun → soil → Sun” would wrongly imply that usable energy cycles in the same way.
Guided practice
Together connect the text’s decomposer sentence to two arrows that are absent from a simple grass–rabbit–hawk chain.
Independent practice
Create a model that includes one transfer across the meadow boundary, such as a rabbit leaving. Write four sentences explaining how that transfer changes the model’s accounting.
Quick assessment
Why is “all nutrients are used up forever when a rabbit dies” inconsistent with this model?
Answer key & assessment criteria
Answers and teaching guidance
- Guided: Add dead material to decomposers and decomposer-released materials to nonliving surroundings/plant uptake.
- Independent: A departing rabbit carries matter and energy outside the chosen boundary. A complete explanation identifies the boundary, transferred material and a limit of the simplified model.
- Quick check: Decomposers can return materials from remains to the environment, where some can be used again; nutrients are not simply destroyed.
Look for: Look for a claim that answers this lesson’s question, accurate use of the supplied evidence and an explanation of a limit or alternative. Ask the learner to point to the detail supporting each inference.
Make it work for your learner
More support
Give separate blue matter-arrow and orange energy-arrow labels; trace one pathway at a time.
Extension challenge
Revise the model to include carbon dioxide exchange and explain why the system is open to both matter and energy.
Selected contributions · Official sources
Standards connections
Selected NGSS band contribution; not complete performance expectation coverage.
Contributes to NGSS performance expectation
MS-LS2-3NGSS · Grades 6–8 band
Model matter cycling and energy moving through an ecosystem.
Read the official performance expectation ↗The model practices selected matter and energy transfers in one ecosystem. It omits quantitative accounting and many organisms and pathways required for a richer ecosystem model.
Source and mapping checked 2026-11-04. This mini-lesson contributes selected skills; it does not claim full attainment.
Supporting Common Core literacy connection
RST.6-8.7Common Core · Grades 6–8
Connect scientific prose with a diagram, model or table.
Read the official standard ↗The provided scientific passage/model is explicitly analyzed in the activity. This selected literacy practice does not establish subject-content alignment or complete coverage of the standard.
Source and mapping checked 2026-11-04. This mini-lesson contributes selected skills; it does not claim full attainment.