1. Yeast experiment round one. Students investigate a model organism to apply ideas about extracellular digestion and to speculate about What happens after extracelluar digestion? How do fungi use sugars? Janet begins by asking what yeast need to live. Then moves to demonstraing how to set up a yeast investigation with yeast, starch and warm water in a flask with a balloon on top of the flask to capture the gas produced. Students are asked to repeat the set-up and make a list of observations and inferences. Janet faciliates a short disucssion on the difference between the two. As students are examining their yeast experiments Janet asks the following questions:
  2. Warm-up. On day 5 students discuss the question: How is the yeast experiment we did yesterday different from doing one with baking soda and vinegar? This is in response to some students skipping the step of describing gas production as a metabolic bio-chemical reaction.
  3. Adding inferences. Students observe the balloon and flask the following day and add to their lists of observations and inferences. Janet asks all students to consider the following questions as they add to their lists:
  4. Whole class conversation of inferences and building an initial model of digestion & respiration. Janet reviews observations and inferences and directs students to attend to gases not to features of the balloon and challenges students to reconsider ideas about heat rising as an explanation for the balloon filling with gas. Has students compare yeast to peppers and strawberries that also produced a gas and inflated a Ziploc bag: What else do fungi do besides extracellular digestion? Janet uses this conversation to launch a conversation about an initial model.
Discussion Questions: 1) Examine the questions Janet asked in this lesson. What was she aiming to do? 2) What alternative conceptions surface? How does she address these? What might have been one way Janet could have revisited these at the end of step 8 above? 3) What was the purpose of linking students’ observations and inferences to their initial model? What function does an initial model serve?
  1. Yeast experiment round one. Students investigate a model organism to apply ideas about extracellular digestion and to speculate about What happens after extracelluar digestion? How do fungi use sugars? Janet begins by asking what yeast need to live. Then moves to demonstraing how to set up a yeast investigation with yeast, starch and warm water in a flask with a balloon on top of the flask to capture the gas produced. Students are asked to repeat the set-up and make a list of observations and inferences. Ms. Buaer faciliates a short disucssion on the difference between the two. As students are examining their yeast experiments Ms. Baurer asks the following questions:
  2. Warm-up. On day 5 students discuss the question: How is the yeast experiment we did yesterday different from doing one with baking soda & vinegar? (This is in response to some students skipping the step of describing gas production as a metabolic bio-chemical reaction)
  3. Adding inferences. Students observe the balloon and flask the following day and add to their lists of observations and inferences. Janet asks all students to consider the following questions as they add to their lists:
  4. Whole class conversation of inferences & building an initial model of digestion & respiration. Janet reviews observations and inferences and directs students to attend to gases not to features of the balloon and challenges students to re-consider ideas about heat rising as an explanation for the balloon filling with gas. Has students compare yeast to peppers and strawberries that also produced a gas and inflated a Ziploc bag: What else do fungi do besides extracellular digestion? Janet uses this conversation to launch a conversation about an initial model.

Discussion Questions: 1) Examine the questions Janet asked in this lesson. What was she aiming to do? 2) What alternative conceptions surface? How does she address these? What might have been one way Janet could have revisited these at the end of step 8 above? 3) What was the purpose of linking students’ observations and inferences to their initial model? What function does an initial model serve?