Prior to the lesson, children had already made some observations and conjectures about the eating cycle of the caterpillar. In particular, they had decided that if frass was observable in the petri dish, then the caterpillar was "digesting" well and would therefore grow. Some students noticed that one caterpillar was not growing as large as the others. They concluded that the caterpillar was not "digesting" its food the way the others were. One child commented that the "sick" caterpillar wasn't eating the right food. He compared it to how he would feel if he ate lots of junk food. Another child questioned this idea, reminding the group that all of the caterpillars were eating the same thing. Throughout our earlier discussions about digestion, the children frequently compared it to their own digestive patterns.
SMALL GROUP TASK DISCUSSION:
When we originally posed the question of "How does the milkweed leaf become caterpillar, we were met with looks of confusion and children claiming "I don't get it". However, after writing their thoughts down for about 10 minutes, the students had some ideas to share with each other. When the small groups met, the discussions opened with the mechanics of eating. For example, one child began by saying, "the caterpillar eats. The leaf goes into its stomach." Groups continued with similar ideas adding on. Mrs. Clement's group recorded that the leaf "goes into the body and after a while it comes out. The frass was the evidence." Another student stated, "the mouth -chomp,chomp- chews the leaf. The leaf goes into the stomach and sits there. The body keeps the good stuff and gets rid of the bad stuff. The bad stuff becomes frass and the good stuff stays in the body." The kids repeated the same ideas that their peers had already shared and the discussion was slow.
Trying to move them towards thinking about food as an energy source, Mrs. Penner draws on the children's tendency to anthropomorphize by restating the question. She writes on chart paper: "I am milkweed. What happens to me?" Once the kids pretended to be milkweed, it was as if they traveled through the caterpillar's body and began to think about all of the possible uses for the food that the caterpillar eats, not just that food goes in and comes out. "The milkweed is breaking into little pieces," responded one student. Another student followed with, "we're getting turned into frass." Many of the children then yell out, "we don't all get turned into frass." Students began to make statements about what they were "turning in to", such as skin, color, fat, muscle, and even energy to move. Finally a student said, "some of us help the caterpillar turn into a butterfly."
Mrs. Clement's group talked a bit about digestion. Students made these comments:
"When we eat food it goes into our tummies and we digest it. Digest means crumple into tiny pieces and dissolve. Acid in our tummies makes the food smaller. Some of the food gets stored in their (caterpillar) bellies and then they push it out their mandibles and it becomes a chrysalis." One student thought that "first the caterpillars start little and then they get bigger. They eat the leaf and it becomes the chrysalis. It's sort of like it's trapped inside." Others also shared similar ideas. Some children seem to believe that the leaf actually becomes the chrysalis. This misconception probably comes from attending to surface similarities between the green milkweed leaf and the green chrysalis.
WHOLE GROUP TASK DISCUSSION:
The small groups reconvened to share their thinking. Reporters from each small group shared what was discussed. The children were expected to be active listeners because they were given the task of listening for something new, curious, challenging, or difficult to understand. They shared their questions after each group reported out. This was an effective teaching model because it helped to both summarize what was said by each group and it gave food for thought about other ways of thinking. For example, children would preface their comments with, "we didn't think of that" and go on to either affirm or elaborate on what was said.
