Decomposers Unit Overview

Decomposers is one of the six Carbon TIME units. If you are new to teaching Carbon TIME, read the Carbon TIME FAQ: Which Units Should I Teach.

The Decomposers Unit supports students in using core disciplinary ideas, science practices, and cross-cutting concepts to develop scientific explanations of how different decomposers transform matter and energy as they grow, move, and function.

Follow these steps to get ready to teach the Decomposers Unit

Lead Editor for 2019 Version

Kirsten D. Edwards, Department of Teacher Education, Michigan State University

Principal Authors

Kirsten D. Edwards, Department of Teacher Education, Michigan State University

Hannah K. Miller, Education Department, Johnson State College

Christa Haverly, Department of Teacher Education, Michigan State University

Christie Morrison Thomas, Department of Teacher Education, Michigan State University

Elizabeth Tompkins, Michigan State University

Charles W. “Andy” Anderson, Department of Teacher Education, Michigan State University

Contributing Authors

Beth Covitt, Jenny Dauer, Jennifer Doherty, Allison Freed, Ellen Holste, Wendy Johnson, Craig Kohn, Emily Scott, Carly Seeterlin, Nick Verbanic

Illustrations

Craig Douglas, Kendra Mojica

This research is supported in part by grants from the National Science Foundation: A Learning Progression-based System for Promoting Understanding of Carbon-transforming Processes (DRL 1020187) and Sustaining Responsive and Rigorous Teaching Based on Carbon TIME (NSF 1440988). Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation or the United States Department of Energy.

Contact the MSU Environmental Literacy Program for more information: EnvLit@msu.edu.

The Driving Question

The Decomposers Unit starts by asking students to express their ideas about the driving question about an anchoring phenomenon, “What happens when bread molds?”

Carbon is the key! In the unit, students learn to tell the story of how matter and energy are transformed as they move through decomposer systems. A particularly powerful strategy for explaining how decomposer systems transform matter and energy involves tracing carbon atoms. For more information about the Next Generation Science Standards disciplinary core ideas included in this unit see the sections on the Matter Movement, Matter Change, and Energy Change Questions below and the Unit Goals.

Research base. This unit is based on learning progression research that describes the resources that students bring to learning about plants and the barriers to understanding that they must overcome. It is organized around an instructional model that engages students in three-dimensional practices.

Students’ Roles and Science Practices

As students learn to answer the driving question by explaining how animal systems transform matter and energy, they play three different roles that encompass all of the Next Generation Science Standards science and engineering practices . (For more details on science and engineering practices, see the Unit Goals.)

Questioners: Students explore the driving question, clarify, and generate more detailed questions
Investigators: Students conduct matter-tracing investigations of bread molding and develop evidence-based arguments about key observations and patterns
Explainers: Students construct model-based explanations of how bread molds.

The roles that students play are embedded in the Carbon TIME instructional model and Discourse Routine. The Discourse Routine guides how classroom discourse aimed first at divergent thinking and then at convergent thinking should be sequenced through the unit.

Good Explanations Answer the Three Questions

Students figure out how to answer the driving question by tracing carbon-containing molecules through a series of movements and chemical changes inside decomposers. At each stage in these processes they answer Three Questions about what is happening: The Matter Movement Question, the Matter Change Question, and the Energy Change Question.

Below, we use the anchoring phenomenon of decomposers as an example of how students learn to answer the Three Questions for different decomposers.

Note that, in Carbon TIME, NGSS crosscutting concepts serve as the “rules of grammar” for producing a scientific performance. With respect to bread molding, high quality explanations should attend to the following rules that are implied by crosscutting concepts. Explanations should attend to:

Scale by explaining events and phenomena at the appropriate scale (see more in the structure and function bullets below).
Systems and system models and energy and matter by following rules for tracing matter and energy through systems and system models. For example, neither energy nor matter should be created or destroyed as it moves into, through, or out of a system.
Structure and function by linking structures and functions in explanations at each scale.
- Macroscopic scale (tracing matter and energy through processes occurring in fungus tissues and organs
- Cellular scale (tracing matter and energy into and out of cells as cellular functions are carried out)
- Atomic-molecular scale (tracing matter and energy through chemical processes—digestion, cellular respiration, and biosynthesis—involving molecules with different structures and properties)

The Matter Movement Question: Tracing Molecules Through Decomposers and Cells

Students learn to tell the following story of how carbon-containing molecules move through decomposers.

Decomposers (fungi and bacteria) live in places where there are large organic molecules (polymers or food) from dead plants or animals
Decomposers excrete digestive enzymes that break large organic molecules into small organic molecules that enter the decomposers
Some large organic molecules are not digested and remain in the environment
Digested small organic molecules (monomers) containing carbon atoms move through fungal hyphae to all cells. Cells use these molecules to do the work that enables fungi to grow and function.
All cells produce carbon dioxide that filters out of fungi and into the air, including air pockets in soil.

The Matter Change and Energy Change Questions: Explaining How Decomposers Use Organic Molecules to Grow, Move, and Function

Matter movement is an essential part of the story, but not the whole story. To answer the driving question, students learn to explain chemical changes that occur inside decomposers.

Digestion. Large organic molecules (polymers) are broken down into small organic molecules (monomers) when bacteria or fungi release digestive enzymes into their food source. Both large and small organic molecules have chemical energy stored in their C-C and C-H bonds.
Biosynthesis and growth. Bacteria and fungi grow when their cells grow and divide through the process of biosynthesis—combining small organic molecules from food to make the large organic molecules needed for cells’ structure and function.
Cellular respiration—energy to move and function. Cells of aerobic decomposers get the energy they need to move and function by combining sugars and other small organic molecules with oxygen, releasing energy when high-energy C-C and C-H bonds are replaced by lower-energy bonds in carbon dioxide and water. (Students can also study the anaerobic process of fermentation in Activity 6.1.)

How Much Detail?

There are more complicated and more scientifically accurate ways of talking about chemical bonds and about changes in energy; we discuss some of those in detail in our educator resource: Carbon TIME Carbon TIME Content Simplifications. But our learning progression research has shown that there is an important tradeoff here—many students get lost in the details and never learn a basic coherent story that answers the driving question. The Next Generation Science Standards take a clear position on this tradeoff; a coherent story based on principles such as matter and energy conservation is more important than the details. Consult the Unit Sequence tab and the sections on Extending the Learning at the end of each Activity page to decide how much detail is appropriate for your students.

Before beginning the Decomposers Unit, you need to decide what to teach and importantly, what not to teach! Use this page to choose the unit sequence that’s most appropriate for your students.

Some activities are REPEATING ACTIVITIES (). Omit these activities if students have already completed them in another unit (unless you’d like students to repeat them as review).
Other activities are TWO-TURTLE ACTIVITIES (), which place a higher demand on students. Decide whether the higher demand required by these activities will be useful or distracting for your students. The Carbon TIME Turtle Trails Document document provides further info about choices for making units more or less demanding, depending on your students’ needs.

Unless otherwise noted in the table below, all activities in the unit should be taught.

Decomposers Unit Sequence and Decisions Table

Here, we present two ways to think about how lessons are sequenced in the Decomposers Unit. The Instructional Model, immediately below, emphasizes how students take on roles of questioner, investigator, and explainer to learn and apply scientific models they can use to answer the driving question. Further below, the Unit Storyline Chart highlights the central question, activity, and answer that students engage with in each lesson of the Decomposers Unit.

Instructional Model

Like all Carbon TIME units, this unit follows an instructional model (IM) designed to support teaching that helps students achieve mastery at answering the driving question through use of disciplinary content, science practices, and crosscutting concepts. To learn more about this design, see the Carbon TIME Instructional Model.

The core of the Carbon TIME IM is the Observation, Patterns, Models (OPM) triangle, which summarizes key aspects to be attended to as the class engages in unit inquiry and explanation. The OPM triangle for the Decomposers Unit, shown below, articulates the key observations students make during the unit investigation, the key patterns they identify through analyzing their investigation data, and the central scientific model that can be used to answer the unit’s driving question. During the inquiry portion of the unit (Lesson 3), the class moves from making observations to identifying patterns, eventually using these patterns to make evidence-based arguments. During the explanation portion of the unit (Lessons 4, 5, and 6), the class learns the atomic-molecular model, makes connections across scales, and uses the atomic-molecular model to explain how decomposers grow, move, and function. Across the unit, classroom discourse is a necessary part of 3-dimensional Carbon TIME learning. The Carbon TIME Discourse Routine document provides guidance for scaffolding this discourse in lessons.

Observations, Patterns, Models, and Explanations in the Decomposers Unit

Unit Storyline Chart

Another way to familiarize yourself with the sequence of lessons in the Decomposers Unit is with the Unit Storyline Chart depicted below. The Unit Storyline Chart summarizes a unit phenomenon-based driving question associated with each lesson, what classes will do in each lesson to address the question, what conclusions they will come to, and how they will transition to a subsequent lesson.

Download Unit IM and Storyline Chart

The tables below show goals for this unit in two forms. A list of Next Generation Science Standards (NGSS) addressed by this unit is followed by a table showing specific target performances for each activity.

Next Generation Science Standards

The Next Generation Science Standards (NGSS) performance expectations that middle and high school students can achieve through completing the Plants Unit are listed below. To read a discussion of how the Carbon TIME project is designed to help students achieve the performances represented in the NGSS, please see Three-dimensional Learning in Carbon TIME.

High School

HS. Chemical Reactions. HS-PS1-4. Develop a model to illustrate that the release or absorption of energy from a chemical reaction system depends upon the changes in total bond energy.

http://www.nextgenscience.org/hsps-cr-chemical-reactions

HS. Chemical Reactions. HS-PS1-7. Use mathematical representations to support the claim that atoms, and therefore mass, are conserved during a chemical reaction.

http://www.nextgenscience.org/hsps-cr-chemical-reactions

HS. Matter and Energy in Organisms and Ecosystems. HS-LS1-6. Construct and revise an explanation based on evidence for how carbon, hydrogen, and oxygen from sugar molecules may combine with other elements to form amino acids and/or other large carbon-based molecules.

http://www.nextgenscience.org/hsls-meoe-matter-energy-organisms-ecosystems

HS. Matter and Energy in Organisms and Ecosystems. HS-LS1-7. Use a model to illustrate that cellular respiration is a chemical process whereby the bonds of food molecules and oxygen molecules are broken and the bonds in new compounds are formed resulting in a net transfer of energy.

http://www.nextgenscience.org/hsls-meoe-matter-energy-organisms-ecosystems

Middle School

MS. Structure and Properties of Matter. MS-PS1-1. Develop models to describe the atomic composition of simple molecules and extended structures.

http://www.nextgenscience.org/msps-spm-structure-properties-matter

MS. Chemical Reactions. MS-PS1-2. Analyze and interpret data on the properties of substances before and after the substances interact to determine if a chemical reaction has occurred.

http://www.nextgenscience.org/msps-cr-chemical-reactions

MS. Chemical Reactions. MS-PS1-5. Develop and use a model to describe how the total number of atoms does not change in a chemical reaction and thus mass is conserved.

http://www.nextgenscience.org/msps-cr-chemical-reactions

MS. Matter and Energy in Organisms and Ecosystems. MS-LS1-7. Develop a model to describe how food is rearranged through chemical reactions forming new molecules that support growth and/or release energy as this matter moves through an organism.

http://www.nextgenscience.org/msls-meoe-matter-energy-organisms-ecosystems

MS. Matter and Energy in Organisms and Ecosystems. MS-LS2-3. Develop a model to describe the cycling of matter and flow of energy among living and nonliving parts of an ecosystem.

http://www.nextgenscience.org/msls-meoe-matter-energy-organisms-ecosystems

Target Performances for Each Activity

All Carbon TIME units are organized around a common purpose: assessing and scaffolding students’ three-dimensional engagement with phenomena. Every Carbon TIME activity has its specific expectation for students’ three-dimensional engagement with phenomena, what we call its target performance. Each activity also includes tools and strategies that teachers can use to asses and scaffold the target performance in rigorous and responsive ways.

The target performances for each activity in the Decomposers unit are listed in the table below.

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Lesson 1 – Pretest and Expressing Ideas and Questions (students as questioners)
Activity	Target Performance
Activity 0.1: Investigation Set Up	Students will make initial measurements of the combined mass of a slide of bread and a Petri dish and leave the bread to mold.
Activity 1.1: Decomposers Unit Pretest	Students show their initial proficiencies for the overall unit goal: Questioning, investigating, and explaining how decomposers move and change matter and energy as they live and grow.
Activity 1.2: Expressing Ideas and Questions about Bread Molding	Students ask and record specific questions about changes in matter and energy in response to the unit driving question: What happens when bread molds?
Lesson 2 – Foundations: Zooming into Organisms (students developing foundational knowledge and practice)
Activity 2.1: Zooming into Plants, Animals, and Decomposers	Students “zoom in” to animals, plants, and decomposers, describing how all of these organisms are made of cells with special structures and functions.
Activity 2.2: Molecules Cells Are Made of	Students use food labels to describe molecules in animal, plant, and decomposer cells: large organic molecules (carbohydrates, proteins, and fats), as well as water, vitamins, and minerals.
Activity 2.3: Molecules in Cells Quiz	Students complete a quiz to assess their understanding of the molecules in cells and how to identify which molecules store chemical energy.
Activity 2.4: Questions about Decomposers	Students describe structures and functions that all decomposers share and pose questions about molding bread to prepare for their upcoming investigation.
Lesson 3 – Investigating Bread Molding (students as investigators and questioners)
Activity 3.1: Predictions and Planning about Bread Molding	Students (a) develop hypotheses about how matter moves and changes and how energy changes when bread molds and (b) make predictions about how they can use their investigation tools—digital balances and BTB—to detect movements and changes in matter.
Activity 3.2: Observing Bread Molding	Students record data about changes in mass and BTB when bread molds and reach consensus about patterns in their data.
Activity 3.3: Evidence-Based Arguments for Bread Molding	Students (a) use data from their investigations to develop evidence-based arguments about how matter moves and changes and how energy changes when bread molds, and (b) identify unanswered questions about matter movement and matter and energy change that the data are insufficient to address.
Lesson 4 –Explaining How Decomposers Move and Function (students as explainers)
Activity 4.1: Molecular Models for Fungi Moving and Functioning: Cellular Respiration	Students use molecular models to explain how carbon, oxygen, and hydrogen atoms are rearranged into new molecules in fungus cells.
Activity 4.2: Explaining How Fungi Move and Function: Cellular Respiration	Students explain how matter moves and changes and how energy changes during cellular respiration in fungus cells.
Lesson 5 – Explaining How Decomposers Grow (students as explainers)
Activity 5.1: Tracing the Processes of Fungi Growing: Digestion and Biosynthesis	Students “zoom in” to the structure and function of a mushroom’s organ systems and cells, tracing atoms and energy.
(Optional) Activity 5.2: Molecular Models for Fungi Growing: Digestion and Biosynthesis	Students use molecular models to explain how polymers are broken into monomers during the process of digestion and monomers are linked into polymers during biosynthesis.
Activity 5.3: Explaining How Fungi Grow: Digestion	Students explain how matter moves and changes and how energy changes during digestion by a fungus.
Activity 5.4: Explaining How Fungi Grow: Biosynthesis	Students explain how matter moves and changes and how energy changes during biosynthesis in a mushroom’s cells.
Lesson 6 – Explaining Other Examples of Decomposers Growing, Moving, and Functioning (students as explainers)
(Optional) Activity 6.1: Exploring Different Kinds of Decomposers	Students explain how matter and energy move and change in other phenomena involving decomposers, included aerobic and anaerobic bacteria, fermentation, spontaneous combustion of hay, and decomposition in forests.
Activity 6.2: Explaining Other Examples of Decomposers Growing, Moving, and Functioning	Students develop integrated accounts of how other fungi (bracket fungi, bread mold, mycorrhizal fungi) grow and function through the processes of digestion, cellular respiration, and biosynthesis.
Activity 6.3: Comparing Decomposers, Plants, and Animals	Students compare how matter moves and changes and how energy changes in decomposers, plants, and animals.
Activity 6.4: Functions of All Decomposers	Students develop integrated accounts of how all aerobic decomposers grow and function through the processes of digestion, cellular respiration, and biosynthesis.
Activity 6.5: Decomposers Unit Posttest	Students show their end-of unit proficiencies for the overall unit goal: Questioning, investigating, and explaining how decomposers move and change matter and energy as they live and grow.

Materials List

Download Zip File of All Unit Materials

Materials to Purchase PDF

Resources You Provide

Pre-Lesson Activity 0.1

Bread slices (4 per group of students)
Digital Balance
Labels for Petri dishes
Permanent marker (1 per group of 4 students)
Petri dishes with 4 lids (4 per group of students)
Roll of tape (1 per group or class)
Spray bottle with water for misting the bread (1 per class or group or class)

Activity 1.1

Pencils (1 per student, for paper version)

Activity 1.2

Sticky notes (1 per student)
Time Lapse Videos of Decomposition

Activity 2.1

Activity 2.2

Activity 2.3

Pencils (1 per student)

Activity 2.4

(From previous lesson) 1.2 Expressing Ideas and Questions Tool for Bread Molding

Activity 3.1

(From previous lesson) Students’ ideas and questions they shared in Activity 1.2 Expressing Ideas and Questions for Bread Molding
(From previous lesson) 1.2 Expressing Ideas and Questions for Bread Molding

Activity 3.2

bromothymol blue (BTB) solution (less than 1 cup per group of four students)
digital balance (1 per group of four students)
plastic Petri dish (1 per group of four students)
labeled Petri dishes with moldy bread from the Pre-Lesson (1 per student)
(From previous lesson) Completed Pre 0.1 Bread Mold Investigation Set Up Worksheet
(From previous lesson) Bread Mold Investigation Class Results 11 x 17 Poster (or Spreadsheet)

Activity 3.3

(from previous lesson) 3.2 Observing Bread Molding Worksheet

Activity 4.1

(From previous lesson) Students’ unanswered questions they shared in Activity 3.3 Evidence-Based Arguments for Bread Molding
(From previous lesson) 3.3 Evidence-Based Arguments Tool for Bread Molding
molecular model kit (1 per pair of students)
scissors (1 per pair of students)
twist ties (at least 12 per pair of students)
video of decomposers moving, such as here https://www.youtube.com/watch?v=3CPCFV46HDs

Activity 4.2