Unit Plan 13 (Grade 5 Science): Decomposers & Nutrient Cycling
Grade 5 unit where students model how decomposers break down dead matter and waste, returning nutrients to soil, air, and water to keep matter cycling in ecosystems.
Focus: Explain and model the role of decomposers in breaking down dead organisms and wastes and returning matter/nutrients to the environment, keeping matter cycling in ecosystems.
Grade Level: 5
Subject Area: Science (Life Science • Earth Systems Connections)
Total Unit Duration: 5 sessions (one week), 50–60 minutes per session
I. Introduction
In this unit, students zoom in on the often “invisible” helpers of ecosystems: decomposers. Building from earlier work with food chains and food webs, they investigate how fungi, bacteria, and small invertebrates (like worms and pill bugs) break down dead plants, dead animals, and waste, returning nutrients to soil, air, and water. Through observations, simulations, and modeling, students learn that decomposers are essential for nutrient cycling and that matter is recycled, not lost. By the end of the week, they create a Decomposer & Nutrient Cycling Model to show these processes clearly.
Essential Questions
- What are decomposers, and what do they do with dead organisms and wastes?
- How do decomposers help matter and nutrients move between living things and the environment?
- What would happen to an ecosystem if decomposers were removed or reduced?
- How can a model help us explain nutrient cycling and the movement of matter involving decomposers?
II. Objectives and Standards
Learning Objectives — Students will be able to:
- Identify and give examples of decomposers (e.g., fungi, bacteria, worms) in different ecosystems.
- Describe, using words and diagrams, how decomposers break down dead organisms and wastes into smaller pieces and nutrients.
- Explain how the breakdown of matter by decomposers returns nutrients to soil, air, and water, making them available to plants (producers) again.
- Develop and revise a model that shows matter moving from plants and animals to decomposers and back to the environment, aligned with 5-LS2-1.
- Create and present a Decomposer & Nutrient Cycling Model Poster or mini-book that clearly communicates decomposers’ role in nutrient cycling and matter movement.
Standards Alignment — 5th Grade (NGSS-Aligned)
- 5-LS2-1 — Develop a model to describe the movement of matter among plants, animals, decomposers, and the environment.
Success Criteria — Student Language
- I can name at least two decomposers and explain what they break down.
- I can describe how decomposers break down dead plants and animals and turn them into nutrients in soil, air, and water.
- I can draw a model that shows matter moving from plants and animals to decomposers, and then back to the environment and plants again.
- I can explain why decomposers are necessary for nutrient cycling and ecosystem health.