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Decomposers | Activity 1.2

Activity 1.2: Expressing Ideas about How Things Decay (30 min)

Students complete the Expressing Ideas Tool for bread molding, helping them document, share, and examine their ideas. There are no “right” answers during this phase of the unit.

Materials You Provide

Resources Provided


Prepare your computer for showing the PPT as well as a time-lapse video of decomposition of various materials: Print one copy of the 1.2 Expressing Ideas Tool for Things Decaying, Big Idea Probe: Leaf Pack Experiment (optional), and 1.2 Decomposers Storyline Reading for each student.


1. Have students discuss the pretest.

Ask students to write down questions they have after taking the pretest (for instance, on the back of their 1.2 Expressing Ideas Tool for Things Decaying). Explain that we will try to answer most of those during the Decomposers Unit.


Use the student responses to the class discussions and also their ideas on the 1.2 Expressing Ideas Tool for Things Decaying, as well as the 1.2 Assessing the Expressing Ideas Tool for Things Decaying to assess their thinking at the beginning of the unit. By the end of the unit, students should be able to explain what happens when animals eat, grow, move, and breathe at macroscopic and atomic molecular scales. For now, listen to students’ ideas, with attention to how they describe matter and energy. Some students may not use principles of conservation of matter to identify rotting materials as the source of mass for decomposers. Students may think that the rotting materials disappear as they decay, and may not recognize that atoms are transferred from the material to the decomposer’s body for growth.


If you are teaching this to multiple classes, you can save different versions of the PPT, with Slide 6 completed for each block. Alternatively, have all classes combine their answers and have students look for similarities and differences.

Extending the Learning

The Cornell Plant Pathology Photo Lab contains a variety of time-lapse movies of fungi, molds, bacteria, slime molds and insects for further illustrations of decomposition: