Student Experience 3: What are decomposers? (Continued)

^[1]

Purposes

1. To help students learn about the various types of organisms that are decomposers.
2. To reinforce that all decomposers, regardless of type of organism, have the same needs (the needs of consumers).

Description

Tell the students that “decomposer” is the name of a category of organisms ^[2].  Ask students to name some of the things they have seen that are decomposers from the video and experiment (e.g., mold and fruit flies).  Ask if they have any other ideas about what organisms are decomposers.

Discuss composting with the class.  Compost, by definition, is “organic matter that has been decomposed and recycled as fertilizer and soil amendment. ^[3]”  Composting involves taking wet organic matter (leaves, food waste) and allowing it to break down into nutrient-rich humus, which can be added to soil for growing plants.  Ask students what they think decomposes the organic matter.  Show students the following clips:

1. Decomposing leaf: https://www.youtube.com/watch?v=cPhfP8Yu7Zs ^[4]

2. Compost time lapse: https://www.youtube.com/watch?v=iAiRNq8JXw8 ^[5]

3. Compost under a microscope: https://www.youtube.com/watch?v=5YKr2JB6qbQ ^[6]

4. Compost under a microscope: https://www.youtube.com/watch?v=sE8R5cTUOtM ^[7]

5. Compost under a microscope: https://www.youtube.com/watch?v=q-gdoznfTPw ^[8] (begin at 2:10; the speaker notes that bacteria are present)

After showing students the five videos, lead a discussion using the Questions to Ask Students.  If students are unclear about anything viewed in the videos, re-view as needed.

Questions to Ask Students

• What types of organisms are decomposers?
• What are the needs of all of the different types of decomposers?

Student Thinking

Some students may have a difficult time understanding that all decomposers are consumers, especially fungi because they don’t move around in the same ways as other types of decomposers.  It is important for them to understand that all decomposers are consumers, and thus all need food, water, and oxygen.

Implementation Tips

• Decomposers include organisms from several groups: bacteria, fungi (e.g., molds, yeasts, and mushrooms), insects, worms, among others.
• In the videos, most of the decomposers seen are microorganisms (organisms that are visible only with a microscope). Bacteria can be seen in the last video, but they are still very small.
• Sound is not necessary for the videos, although it might be useful with the 2^nd and 5^th videos in the above list.