Middle School • Fungi and life processes • Legacy Series


Last year Ms. Bauer taught a unit on fungi but had the sense that the unit was dry and that the students were not able to retain a lot of the information they learned. The focus was on fungi as a kingdom and the students learned about the phyla within the kingdom. They did a series of activities such as a mushroom walk around the school, making spore prints, and learning about the ecological role of fungi. They also did an experiment to create the “best recipe” for yeast metabolism. The students were actively involved in the experiment but their focus tended to be on how much carbon dioxide was produced by the yeast. Students read about the role of sugar in cellular respiration and chose to manipulate the carbohydrates and sugars they gave to the yeast but some students also chose to add items like lemon juice. Most students understood a chemical reaction took place but some students did not attribute the reaction to a metabolic process in the yeast–visualizing something more like vinegar and baking soda as the reason for gas production.

This year Ms. Bauer shifted the focus of the unit to the interrelationships of fungi life processes. Fungi were used as examples to show how these life processes characteristic of all living things. She chose to focus on the role of fungi in decomposing matter, how they digest matter, how they use cellular respiration to generate energy from sugars and why they use this energy—which is chiefly used for reproduction. In this way the unit shifted from being about yeast as a topic with some focus on processes east do to being about an explanation for why yeast decompose matter.

Students worked to develop the following model, which includes the processes of extra-cellular digestion, absorption, and cellular respiration:
Complex carbohydrates + enzymes > sugar and oxygen > energy + carbon dioxide

To focus the students on the idea that yeast exemplify processes of all living things and to generate student interest, Ms. Bauer used the essential question “How am I similar/different than a fungi?” to frame the unit.

Pre-unit interview with the teacher
Throughout the unit the students are working on developing a model of the interrelationships of fungi processes. Each activity layers on more background information so that by the end on the unit students are able to construct a model showing the interrelationships of digestion, respirations and reproduction in order to explain what decomposers do and how they use the energy harnessed by these processes. To better understand digestion and respiration in yeast, students construct and modify a digestion-respiration model.

After learning about digestion students do one round of yeast investigations in which they make inferences about observations such as the production of gas. The design a model based on their observations. Then after learning about respiration students engage in more open-ended inquiries to better understand both digestion and respiration. They use information from the yeast experiment and texts to modify their model. Janet (Ms. Bauer) scaffolds the students’ use of science concepts in written explanations by having students construct concept maps as pre-writing assignments. Students first do a concept map with ideas related to extracellular digestion and later do another with terms related to decomposition, digestion, respiration and reproduction.

Students use both of the maps to write an explanation for why strawberries rot over time. She not only scaffolds students’ use of science ideas but she asks students to participate in model-building as a scientific endeavor. In terms of “thinking like a scientist,” Ms. Bauer also helps her students use evidence-based explanations. During the yeast investigation she constantly presses students to connect what they are seeing to what unobservable processes might be taking place.

In this way, Ms. Bauer moves beyond just asking students to describe what variables they are manipulating and beyond just giving students background information to help students focus on unobservables during the investigation but rather her focus is on model-based inquiry and teaching students about the nature of scientific work.

1) Elicitation of student experiences. Janet rapidly asks almost all students to state where they have seen fungi before without much comment on these experiences.
2) Examination of pictures and samples of mushrooms, mold on bread and mold on fruit/vegetables in Ziploc bags. Materials rotate every 7 minutes for the purpose of infusing a new idea for small groups to think about without the teacher being present to press students. Teacher circulates, using back-pocket questions to elicit more observations. For example:

  • For the picture of the mold on an orange- Do you think this is one organism or many organisms?
  • What did you notice about the moldy fruit? Why do you think it is squishy and has a liquid at the bottom of the bag?

Students answer questions on worksheet that probes students’ initial ideas about fungi processes:

  • What are examples of different kinds of fungi?
  • Where can you find fungi?
  • What characteristics make fungi different from plants?
  • How are fungi different from us?
  • How might fungi be similar to plants and animals?
  • What basic things do fungi need in order to survive? What kinds of things do they need to be able to do in order to survive?

3) Whole-class debrief. Teacher constructs a class concept map of students’ initial ideas and questions. In the middle of the map she writes the essential question and then groups the students’ ideas on the map (according to ideas about decomposition, digestion/nutrition, environmental conditions, reproduction, and growth). Students are asked to write at least 2 questions they have about fungi for homework. These are recorded the following day.

Discussion questions for teachers: 1) Ms. Bauer chose to spend 1 ½ days eliciting what students’ know about decomposition, digestion and respiration. What are students’ initial understandings? 2) How does she uncover these ideas? What kinds of questions does she ask when students give incomplete responses or reveal an alternative conception? What does she do when she first enters a group/ exits a group?

Elicitation of student experiences
Building background knowledge
1) Warm-up. What are some ways fungi affect you?

2) Students read background information & make sense of the information. Teacher circulates and asks students to make sense of the information they read on the back side of the picture packets from the previous day.

Students answer the following questions in their notebooks:

  • What roles do fungi play in the world?
  • What types of organisms are affected by fungi? Cite several specific examples.

They are also prompted to use the information to revise any of their responses to the worksheet from the previous day. Janet also asks 2 key back pocket questions:

  • Did fungi cause the rotting or do the fungi grow on rotting things?
  • If fungi don’t move, what might they need energy for?

3) Optional challenge. For homework students can opt to do challenge problems: a) to further research fungi and their roles in a particular habitat (i.e. their back yard, North Cascade Mountain range, etc.) and b) to draw what this environment would look like if there were no fungi present.

Discussion questions for teachers: 1) Which concepts has Ms. Bauer chosen to build first? Why? 2) What issues of academic language surface in this lesson?

Initial explanations of decomposition and extracellular digestion
1) Warm-up. Make 3 observations of the strawberries in the bag. Teacher solicites students’ ideas about the diffences between observations and inferences then students’ observations.

2) Initial explanations. Students are asked to tell a story of the “forgotten strawberry” on day 1, day 10 and day 20. The story is about a student who left a bag of strawberries in a lunch bag. Students are asked to use the terms digestion, decomposing, nutrients and rotting in their stories.

Janet uses this time to press students on their understanding of “rotting” and “decomposition” (a distinction the students made the day before) and about growth and reproduction because students seemed to be drawing parallels with bacterial growth and reproduction.

3) Building content knowledge though concept mapping. Students return to their picture packets and are asked to use the written information to make a concept map for extracellular digestion in their notebooks with the following terms: enzymes, extracellular digestion, sugars, starches, nutrients, decomposing and rotting. Teacher asks questions that aid students in making connections among concepts.

4) Refining the story. For homework students write their stories of the forgotten strawberry using the key terms discussed in class.

5) Class concept map. On day 4, the teacher solicits students’ ideas about connections among terms they included in their concept maps on the previous day. Teacher synthesizes these with students and develops a class concept map for extracellular digestion. Students modify their concept maps in their notebooks based on the whole class discussion.

Discussion questions for teachers: 1) How did Ms. Bauer attend to issues of academic language in this lesson?

Yeast experiment Round 1
1) Yeast experiment round one. Students investigate a model organism to apply ideas about extracellular digestion and to speculate about “What happens after extra-celluar digestion? How do fungi use sugars?” Janet begins by asking what yeast need to live. Then moves to demonstrating 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 facilitates a short discussion on the difference between the two. As students are examining their yeast experiments Janet asks the following questions:

  • When you say yeast rises, what is that referring to? When bread is made, it double in size…why?
  • If we could magnify what was happening inside the flask, what could we see happening?
  • What’s happening to the balloon? How is this different from 10 minutes ago…why? What might happen if you observed this balloon over an hour?
  • What is the “stuff” you see all over the inside the flask and bubbling up on top of your yeast+starch solution?
  • Where is the gas coming from?
  • What is that energy used for?

1) 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)

2) Adding inferences. Students observe the balloon and flask the following day and add to their lists of observations and inferences. Ms. Bauer asks all students to consider the following questions as they add to their lists:

  • What are the things you started off with? Think about things you can’t see.
  • Why didn’t the balloon get bigger?
  • Why is the balloon inflated?

3) Whole class conversation of inferences & building an initial model of digestion & respiration. Ms. Bauer 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?” Ms. Bauer uses this conversation to launch a conversation about an initial model.

Discussion questions for teachers: 1) Examine the questions Ms. Bauer 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 Ms. Bauer could have revisited these at the end of step 3 above? 3) What was the purpose of linking students’ observations and inferences to their initial model? What function does an initial model serve?

Building knowledge about respiration & refining the model
1) Building content knowledge about respiration. Students answer questions to increase their content knowledge about cellular respiration. They use laptops in the classroom to investigate these questions for Activity 47: The Yeast of our Worries:

  • Is yeast alive in the packet? Explain. What other information can you find about yeast bought in packets at the grocery store?
  • In Act. 45, Ms. B used warm tap water to make the starch solution for the yeast. Explain why. What information can you find about yeast and temperature?
  • Why does it say RISING yeast on the packet of yeast? When you make bread with yeast, the dough will “rise”. What information can you find about dough and rising? (What’s going on with the yeast and the rising of the dough?)
  • We know that fungi can use their enzymes to break down starches. Starches can also be called complex carbohydrates. In Act 45, you used flour, a complex carbohydrate. What are examples of other types of foods that are complex carbohydrates?
  • How might changing the type of complex carbohydrate in Act 45 affect the yeast and the amount of gas in the balloon? Explain.
  • If starches are complex carbohydrates, then sugars are simple carbohydrates. Regular table sugar is a simple carbohydrate. What are examples of other types of foods that are simple carbohydrates?
  • How might changing the type of simple carbohydrate in Act 45 affect the yeast and the amount of gas in the balloon? Explain.

2) Adding to the model. Janet facilitates a whole-class discussion about the information that needs to be added to their initial model (information about starches, sugars, temperature) and students consider how they could test some part of the model.

Discussion question for teachers: What and how does Ms. Bauer encourage students to add to the class model? 2) How many students still hold onto alternative ideas about why the balloon is filling? What questions and activities helped students reconsider their initial hypotheses?

Investigating digestion & respiration in yeast
1) Warm-up Conversation. How are these processes similar and different for you and fungi? Janet focuses students on connections between human biological processes & fungi biological processes and re-orients students to the extracellular digestion à cellular respiration model.

2) Preparing students for round 2 investigation with yeast. Teacher uses a whole-class pre-discussion linking typical “experimental design” conversation with a discussion about the extracellular digestion à cellular respiration model. She asks:

  • What would you learn from changing temperature? Which part of the process will be affected? Think through the whole equation.
  • What will we be able to see?
  • What would you learn from changing amount of food? Predict what will happen if it has too many carbs or too few?

3) Choose an experiment. Students work with groups to select one question to investigate.

  • 1. Do yeast have to go through extracellular digestion to produce energy?
  • 2. How does temperature affect digestion and energy production?
  • 3. What happens if yeast have too many or not enough nutrients?

4) Hypothesis writing. Teacher makes rounds to groups to help design experiments & craft rich hypotheses about how the experiments will test & inform parts of the digestion > respiration model.

5) Warm-up Conversation. On day 8 Janet leads a whole-class conversation about predictions from each of three experiment options. Teacher compares similarities and differences between groups doing the same experiments and presses students to define which part of the model they are testing (extracellular digestion, cellular respiration or both).

6) Revising hypotheses. Teacher presses students to use ideas from the digestion à respiration model to elaborate their initial predictions by adding unobservables to their tentative explanations. Students are asked to circle these words in their hypotheses.

7) Applying models to evidence. The teacher visits each group during data collection to press students to relate what they are seeing to the big ideas within the model.

Discussion questions for teachers: 1) For days 7 and 8 choose 1 line of experimentation—temperature-option 2 or starch vs. sugar-option 1—and track how students’ language about the experiment and the big ideas changed. 2) Make a list of 4 or 5 productive back-pocket questions Ms. Bauer asks and describe how or why each was productive in revealing student thinking.

Generating evidence-based explanations
1) Warm-up. Students are asked to reflect on their predictions drawing attention to observables & to the processes that cause the observable changes to happen.

2) Discussion of what counts as evidence, what makes data relevant, and what makes a good conclusion statement.

3) Pressing for evidence-based explanations during the investigation. Teacher presses students to go beyond simply restating their observations in their “conclusions” paragraph by pushing students to connect observable data (balloon size, volume of liquid) with unobservable processes that are part of the original models (digestion, enzyme activity, respiration, reproduction). The teacher uses several “what if” questions to help students describe what did happen.

  • What would happen if we left this until tomorrow?
  • What if we kept it at the same temperature all night?
  • What would happen if we added 50g of sugar?

4) Cross-comparing findings and explanations. Groups meet with other groups who conducted similar experiments to compare findings & explanations.

5) Identifying presenter and audience roles. Teacher brainstorms questions students can ask one another when listening to other groups presenting. She directs both presenters and listeners to focus on the underlying explanation.

6) Group presentations of findings and Q & A from peers. Groups write a final explanation then present their findings and explanations. Peers record ideas about experiments they did not conduct and pose questions about the findings/explanations.

Discussion questions for teachers: 1) For days 9 & 10 continue to track 1 line of experimentation–and track how students’ language about the experiment and the big ideas changed. 2) For days 9 & 10 what scaffolds does Ms. Bauer use to support students in generating spoken and written evidence-based explanations?

Applying and extending the model
1) Applying the model. Students employ ideas from the yeast experiments and the digestion à respiration model to explain why yeast inflate the balloon only to a certain circumference and then it does not really inflate anymore. The teacher helps students layer on ideas about limiting reactants and conditions for metabolic reactions.

2) Revising the model. Students add new ideas (from yeast experiments) to the digestionàrespiration models in their journals.

Discussion questions for teachers :1) How does Ms. Bauer use this lesson to help students wrestle with unobservable ideas that the students had not fully considered to date? 2) What other phenomena might students be able to explain now?

Folding in reproduction
1) Examining reproduction in more detail. The teacher has the students do Activity 48: Fungi Reproduction. The activity has a reading for the students to do and then students complete a chart of the different types of reproductive methods fungi use. Students also examine two websites that show growth and division of budding yeast and binary fission of bacteria. Students also make a graph of a number of yeast cells vs. time and answer:

  • How many yeast do you predict there would be at 60 and 100 seconds? Why?
  • Based on your understanding of yeast budding, and digestion and respiration, explain why the number of yeast in a closed container would eventually start to decrease.

Lastly students respond to the question: Why do fungi put so much energy into reproduction?

2) Post-assignment conversation. The teacher has students share and revise their responses. She asks:

  • Why is it that you don’t see fungi growing on your bread right away?
  • Are the bread mold individuals growing or are these more individuals?
  • Compare how we use energy versus how fungi use energy.

Discussion question for teachers: Which student ideas about reproduction does Ms. Bauer revisit from Days 1 &2? How does she support students in extending their thinking?

Synthesizing all ideas and generating a new representation
1) Concept mapping. In small groups students discuss how ideas throughout the unit relate. They make unit concept maps indicating connections among ideas and then provide peer critique/feedback on others’ concept maps.

2) Whole-class debrief. Students summarize the missing links they saw on the concept maps.

3) Summative assessment. Students use the concept mapping activity to write a revised story of the forgotten strawberry.

Discussion questions for teachers:1) What kinds of student thinking are afforded by this lesson? 2) How might you tweak this lesson to help students differentiate between major ideas (cellular respiration) and minor ideas (enzymes)? 3) Create an explanation rubric and evaluate 9 students’ revised stories of the forgotten strawberry, detailing partial as well as complete understandings.

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