Activity 5.3: Explaining How Fungi Grow: Digestion(40 min)

Using slide 3 of the PPT have students revisit their arguments and unanswered questions from the Bread Molding Investigation by looking at 3.3 Evidence-Based Arguments Tool for Bread Molding.

• Remind students that after explaining cellular respiration in Lesson 4.2 there were still unanswered questions about how decomposers grow and where the glucose needed for cellular respiration comes from.
• In today’s lesson, students will use what they learned in Lesson 5.1 (and 5.2) to explain how fungi get food to their body’s cells and how fungi use food for growth.

Use slides 4-5 of the 5.3 Explaining How Fungi Grow: Digestion PPT to guide students through a review of digestion.

• Use Slide 4 to review how decomposers use food to grow. Ask students for their ideas about what they remember from the previous activity.
• Use slides 5 to remind students what happens to the food that IS digested: Large organic molecules (polymers) are divided into small organic molecules (monomers) that go into the hyphal cells.
• Display the following posters in your classroom to help students visualize the digestion of polymers to monomers.
• Carbohydrates: Use the Digestion and Biosynthesis of Carbohydrates 11 x 17 Poster to offer students a visualization of how polymers like starch (which is a type of carbohydrate) are broken apart into monomers like glucose.
• Fat: Use the Digestion and Biosynthesis of Fat 11 x 17 Poster to offer students a visualization of how polymers like fat are broken apart into monomers like fatty acids and glycerol.
• Proteins: Use the Digestion and Biosynthesis of Protein 11 x 17 Poster to offer students a visualization of how polymers like proteins are broken down into amino acids.
• Note: If you only taught 5.1, you can use the posters to help students visualize the process, but do not need to focus on the names of the small organic molecules.

Show slide 6 of the 5.3 Explaining How Fungi Grow: Digestion PPT. Give each student one copy of 5.3 Explanations Tool for Fungi Digestion.

• Tell students that in this part of the investigation, they will combine everything they learned about how fungi get food to their body’s cells into an explanation.
• Remind them to consider both their evidence from the investigation as well as what they learned in the molecular modeling (or tracing) activity to construct their explanations.
• Give students about 10 minutes to complete the Explanations process tool.

Show slide 7 of the 5.3 Explaining How Fungi Grow: Digestion PPT. Divide students into pairs and have them compare explanations for the Three Questions and the final explanation on the process tool.

• Have students use the Three Questions 11x17 Poster (or Three Questions Handout) as a reference. Have students check their explanations with the middle and right-hand columns of the poster or handout to make sure they are following the “rules.”

Use slides 8-14 in the PPT to have the students discuss what is happening to matter during digestion and to have them check their answers to the Matter Movement Question on their 5.3 Explanations Tool for Fungi Digestion.

• Show students slides 8-10 to have them think about where atoms are moving from and moving to during digestion.
• Display slides 11-14 to have students compare their answers to the Matter Movement Question with the answers on the slides. Have students use a different colored writing utensil to make any needed changes to their answers. Allow students to ask questions if they do not understand why their ideas are incorrect.
• If students have model explanations to share, display student work and discuss. If students have common areas of weakness in their explanations, ask for a volunteer to share, display student work, and discuss ways of strengthening the response.

Show slide 15 to begin discussion the Matter Change Question.

• Display slides 16-17 to have students compare their answers to the Matter Change Question on the 5.3 Explanations Tool for Fungi Digestion with the answers on the slide. Have students use a different colored writing utensil to make any needed changes to their answers. Allow students to ask questions if they do not understand why their ideas are incorrect.
• If students have model explanations to share, display student work and discuss. If students have common areas of weakness in their explanations, ask for a volunteer to share, display student work, and discuss ways of strengthening the response.

Display slide 18 to begin discussing the Energy Change Question.

• Display slide 19 to have students compares their answers to the Energy Change Question on the 5.3 Explanations Tool for Fungi Digestion with the answers on the slide. Have students use a different colored writing utensil to make any needed changes to their answers. Allow students to ask questions if they do not understand why their ideas are incorrect.
• If students have model explanations to share, display student work and discuss. If students have common areas of weakness in their explanations, ask for a volunteer to share, display student work, and discuss ways of strengthening the response.

Display slide 20 of the PPT. Have students look at two handouts: (a) the Three Questions Handout, and (b) the Example Decomposers Explanations Handout.

• Ask students to evaluate the two example explanations of fungi digestion: Which explanation is better? Why?
• Have students use the Three Questions Explanation Checklist on the back of the Three Questions Handout to justify their critiques of the explanations.

Display slide 20 of the PPT for the full explanation. Have students use the Three Questions Explanation Checklist on the back of the Three Questions Handout to check that their story includes each of the parts (matter movement, matter change, energy change, and matter movement) and answers the prompt in a cohesive way.

• If students don’t have all four parts in their explanation, instruct them to add to their explanation using a different colored writing utensil.

If students have model explanations to share, display student work and discuss. If students have common areas of weakness in their explanations, ask for a volunteer to share, display student work, and discuss ways of strengthening the response.

Pass out 5.3 How do Decomposers Digest Food? Reading. The reading provides a summary explanation of digestion and additional information about a connection between decomposers and biofuels. Higher level students may not need the review of content provided in this reading, but you may want them to add to the Decomposers Matter Tracing Tool started in Activity 4.2. Have students read using the Questions, Connections, Questions Student Reading Strategy. See the Questions, Connections, Questions Reading Strategy Educator Resource document for information about how to engage students with this strategy.

• After pairs are finished reading, have students share with the class what they found interesting and any questions they have.
• After discussion, students can complete the digestion section of the Decomposers Matter Tracing Tool that they started completing in Activity 4.2.

Show slide 21. Have students look at the Decomposer 11 x 17 Poster and discuss with a partner the parts of a fungus involved in digestion on a macroscopic scale.

• Tell students that digestion occurs outside the hyphal cells.

Show slide 22 of the 5.3 Explaining How Fungi Grow: Digestion PPT.

• On a sheet of paper or a sticky note, have students individually answer the exit ticket questions. Depending on time, you may have students answer both questions, assign students to answer a particular question, or let students choose one question to answer. Collect and review the answers.
  • Conclusions: How does a decomposer digest food?
  • Predictions: How do you think a mushroom uses digested food to grow?
• The conclusions question will provide you with information about what your students are taking away from the activity. Student answers to the conclusions question can be used on the Driving Questions Board (if you are using one). The predictions question allows students to begin thinking about the next activity and allows you to assess their current ideas as you prepare for the next activity. Student answers to the predictions question can be used as a lead into the next activity.