Mealworms Redux

I would have thought mealworm investigations were pretty standard in the elementary grades - observation skills, life cycles/metamorphosis, a few controlled experiments varying types of food, etc.

I decided to bring the investigations into my 8th grade Regents Biology classes, simply because I wanted an inexpensive object of long-term observations and a vehicle for discussing things like variation, adaptation, reproduction & development, heredity (to the extent possible within our time constraints), ecology - niches, etc. A lot of content can be related to the mealworms and I can also get students to do controlled experiments that will be part of their required grade 8 project here in NYC.

So far the students are enjoying their investigations. We have completed most of the preliminary observations of the larval stage (the “worm” stage) and are now setting up a couple of simple controlled experiments that will vary the kinds of food they eat, for example, and chart their growth over a couple of weeks. Most of my students, surprisingly, have never done any mealworm investigations. The few that have seen them before did so in the 2nd grade, so they certainly don’t mind revisiting them and looking at them through 8th grade eyes.

I’m not exactly sure how long a complete life cycle will take given our classroom conditions, but they should be able to come up with some more interesting investigations that they will do individually or in pairs to complete their long-term projects – investigations involving other stages of development, for example, transition times, etc.

I’m trying to transition from mental models/black boxes to mealworms and then to Darwin’s model of evolution through natural selection. I'll give more details as I work it out, but the main transitional concept will be variation, as we look at differences among our mealworms in terms of observable features, behaviors, growth patterns, etc.

Mental Model Details & Analysis

I'm wrapping up my black box/mental models activity this weekend - students are completing their lab sheets for homework. Nothing ever goes as expected. Given that fact, I'm happy with the way the activity came across, and I believe it's a nice springboard for the rest of the year, where the question of how scientists work and how they "know" what they know will come up again and again, especially now when we begin our evolution unit and consider Darwin's model. I was pre-viewing PBS's Evolution video, and struck by the similarities between our black box activity and the struggles of scientists in his day to explain the origin of species.

Let me demonstrate a little. Here's one example of a black box I set up:

(There are 3 other arrangements. Again, this is an activity I adapted from FOSS: Models & Designs.) I use a lot of tape, having learned a long time ago that the impulse to cheat is irresistible. There's a little ball inside, and it runs up against these cardboard or foamboard obstacles. Students have to figure out what's inside the box based on the sound and feel of the moving object. I don't tell them anything about what's inside. They usually focus first on the moving object, and the most common inferences were marble or battery. Battery seems an odd guess, but the obstacles make the object move in strange ways, and a cylindrical shape is a plausible explanation with some of the boxes. At some point during our discussions, a student will object to the battery hypothesis and propose that there are other things in the box (obstacles or whatever) that cause the marble to move in funny ways. Students argue and become quite attached to their ideas, holding on in the face of strong evidence against them - this activity mirrors what happens in the "real" scientific community in many ways!

Keep in mind this module from FOSS is geared toward 5-6th graders, and I can't imagine why. My 8th graders have a very low tolerance for intellectual frustration and had difficulty devising any methodology for figuring out what was inside. Some students sat there repeatedly, incessantly shaking the box near their ears, even a few days into the activity, expecting some magical voice, I suppose, to reveal the contents to them. I modeled a few strategies for how to work the box without announcing that I was modeling a strategy - rolling the moving object around the perimeter, noting where there was an obstacle, mapping it on a piece of paper, etc. I should have announced it. Toward the end I thought of another technique, and had students tape an index card directly to the box and start marking where the obstacles were. That was a big help and I wish I had thought of it earlier.

Oh, what is the twist that I added to the original FOSS idea? I used a steel ball instead of a glass marble. At a certain point I alleviated some frustration by asking student to focus on the moving object. Some had suggested a marble. We discussed what a marble was - a glass sphere - and whether it might be something other than glass. Was there any test we could do to determine if it was glass or not? What else might it be made of - wood, rubber, metal - could we do any kind of test that would tell us if it were any of those materials? Someone suggested if it were metal, it would be attracted to a magnet. So out come the magnets. Now we have not only narrowed down the possible materials that the object could be made of, we have a new tool or technology for manipulating the object and creating a map of the inside of the box. A lot of scientific method here, and a little messy like real science can be. Observations, tentative explanations or hypotheses, testing hypotheses, revising the model, arguing, sharing information, inspiration, using technology to refine the model, and so on.

You can download the lab sheet I made with some notes here (MSWord). This is my original lab, without any modifications. I would certainly revise some of it in light of my experiences, but at the moment I'm focusing on the next unit and cannot revise it now. I definitely guided students more than I wanted to, but I had to balance the process of discovery against the frustration level that sometimes threatened to undermine the process anyway. If I have time I will post a student example later this week.

UPDATE

Here's a nice alternative activity from Exloratorium if you can trust your students not to cheat!

Mental Models

I have been spending the first classes this year for my regents students working with the idea of mental models. I discuss the rationale briefly in my course outline. The activity itself is derived from the FOSS Models & Designs curriculum, but I have thrown in an additional twist. I will post a fuller description of the activity itself after my students have finished with it, but basically it's literally a black box with something going on inside that students have to figure out using the sounds it makes and the feeling of it as the thing inside the box (a marble? a battery? a rock? were some of the hypotheses) moves around.

It is a great model of the scientific process, involving observation, reasoning, asking questions, testing, collaboration & communication. So far I think the activity is going over well, despite a good deal of necessary frustration and the usual attempts to circumvent the process (i.e., cheat). I try to look at this in a positive way, acknowledging the importance of curiosity and our need to know, while at the same time comparing it to a video game, in which the fun is all in playing the game, not necessarily getting to the end of the game or "winning"- what fun would a video game be if there were a cheat button where you could immediately destroy all the bad guys and win - game over. In this activity, the contents of the box are trivial and unimportant - it's the process of discovery that matters, how we figure out what's in the black box.

The twist that I've added to the FOSS idea will allow students to use a new "technology" to gain a better understanding of what's going on. I won't reveal the twist until the students have gone through it. I will say, however, that the idea came to me while reviewing the history of the discovery of the atom and it's structure. Thompson's "plum pudding" model (no nucleus) was replaced by Rutherford's (and later Bohr's) nuclear model (electrons "orbiting" a central nucleus). Rutherford came up with the model after experiments in which alpha particles were fired at gold foil - most went straight through the foil, but a few bounced back, a phenomenon incompatible with the idea of an atom with uniform density, and thus the tiny, dense, central nucleus was postulated. Suddenly it occured to me...TBA