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Decomposers | Lesson 1 - Pretest and Expressing Ideas

Lesson 1: Pretest and Expressing Ideas

In this lesson, students take a pretest and share their initial ideas about how things decay, identifying what decomposers need to grow and gain mass.

Guiding Question

What happens when things decay?

Activities in this Lesson

  • Activity 1.1: Decomposers Unit Pretest (20 min)
  • Activity 1.2: Expressing Ideas about How Things Decay (30 min)


This lesson helps students start thinking about all of the unit objectives, but does not feature a mastery of any of them.

NGSS Performance Expectations

This lesson helps students start thinking about all of the unit NGSS Performance Expectations, but does not feature a mastery of any of them.

Background Information

The pretest and discussion in this lesson (a) help students to anticipate and begin thinking about the questions that they will answer in this lesson and (b) help you as a teacher see how your students reason about how matter and energy are transformed when things decay (digestion, biosynthesis, and cellular respiration in decomposers). In the Application Activity Sequence, both activity 1.1 and activity 1.2 in this lesson serve as the “Establish the Problem” phase for all the activities in the Decomposers unit.

In Activity 1.1, the unit pretest is useful for two purposes. Your students’ responses will help you decide how much detail you want to include during the unit, particularly details about chemical structures of materials. If your students are mostly at Level 2 in the carbon learning progression, you may want to focus on the main ideas (like the tracing of matter and energy and the Three Questions) rather than chemical structures. Your students’ responses will also provide a starting point for discussions about the focus for this unit.

In Activity 1.2, through the discussion students will come to recognize that they have many different ideas about what happens when things decay, as well as unanswered questions. We expect many students to express Level 2 or Level 3 ideas, for example, that decomposers grow because their cells divide, or that gas has no mass, or that decay is not related to decomposers.

Key Carbon-Transforming Processes: Digestion, Biosynthesis, and Cellular Respiration

See the Decomposers Unit Read Me document for more details.


Unit Map

Decomposers Lesson 1 Unit Map

Talk and Writing

At this stage in the unit, the students will be Expressing Ideas. The table below shows specific talk and writing goals for this phase of the unit.

Talk and Writing Goals for Expressing Ideas Phase

Teacher Talk Strategies that Support this Goal

Curriculum Components that Support this Goal

Treat this as brainstorming and elicitation.

Remember, there are no “right” answers at this point. We want to hear all ideas.

Unit Pretest

My Students’ Answers

Listen for ideas about what is happening to matter and energy at different scales.

Where did the energy come from?

Where does the matter go next?

Are you talking about matter or energy?

What about the atomic-molecular scale?

What about the cellular scale?

Unit Pretest

Expressing Ideas Process Tool

Listen for a wide range of student ideas. Press for more complete ideas.

Who can add to that?

What do you mean by _____? Say more.

So I think you said _____. Is that right?


Have students compare, contrast, and document their ideas.

Who has a different idea?

How are those ideas similar/different?

Who can rephrase ________’s idea?

Let’s record our ideas so we can come back to them and see how our ideas change.

Sticky notes on the class poster

Activity 1.2 PPT

Encourage students to provide evidence for their ideas.

How do you know that?

What have you seen in the world that makes you think that?

Sticky notes on the class poster.