I put together a "lab" on living vs non-living things. I still don't like the way this subject is treated in texts and I still haven't got a good lab to go with it - and yet I think what could be more fundamental to a biology class than understanding what a living thing is? I think I know why I'm having trouble. My pie in the sky curriculum would incorporate this question into a culminating activity, rather than an opening activity - yes, begin with the question "what is "life," but let the students develop the idea over the course of a year's study rather than cramming the "characteristics of life" down their throats (OK, drumming it into their heads? Pick your cliche) as a content objective to be more or less memorized at the beginning of the year.
So I've spent several days in class on the activity and devoted ridiculous amounts of time to thinking about and planning it, only to realize that it just doesn't fit in or work as a one-shot lesson or activity. It's not too late to salvage some things from it, but I need to think more long-term about how to keep the question alive, no pun intended, throughout the year.
I have this tendency also to overcomplexificate. I have too many things going on in the activity and that, in part, leads to a lack of a clear message to the students. So let me summarize the lab. It's a pretty standard sorting of things into categories. Some are living, some non-living, and some - heck, I'm not even sure how to classify within that dichotomy. In my mind I had created a different set of categories that includes living/non-living, but adds a group of "dead" things such as beef jerky and a dried bay leaf, and a group of things "derived from living things" like milk, gummi bears, and apple juice*. At the time I thought it would be a great idea to incorporate some dichotomous sorting strategy into the lab. I also thought it should be an open-ended task. Big mistakes for a couple of reasons.
First, a lot of the sorting criteria used by the students generated ridiculous amounts of discussion - I know, that sounds like a good thing, but remember the objective here is to introduce the idea that living things share certain characteristics yadayadayada. So now I've opened up whole other areas of debate including natural vs. unnatural, edible and non-edible, etc. Great topics for discussion and ultimately relevant, but a distraction from the objectives of the lab/unit at hand. I guess that underscores why we prefer to use observable features as sorting criteria.
Secondly, students don't have enough information in front of them to really get into the content I want them to get nor do they have the prior knowledge to focus in on it. There's no way they are going to infer or observe most of the characteristics of living things going on in front of them, especially not in a single lab period or two. Or to know that gummi bears are made of gelatinous proteins and sugar, neither of which is "alive" but both of which are derived from living things. How would they know or observe that? Again, this is an argument for thinking of this question as a long-term inquiry investigation that should be infused into the course and revisited at appropriate times.
At the suggestion of my science coach, I did include a section of the lab worksheet for students to write down any of these questions that came up. I will pick the more interesting ones to put up (A "Wonder Wall") around the room and return to them at appropriate times during the year. I had done this kind of thing in the past, but for some reason I stopped doing it in the last few years. It's a good habit to get back into.
*Items for sorting included a mealworm (live), a sprig of mint (alive I think), acorns (freshly harvested from the park), a glass marble, a rock, a paper clip, coffee beans (roasted), and the above mentioned beef jerky, dried bay leaf, powdered milk, and apple juice. I would post the lab sheets, but they were frankly a disaster in practice. I will simplify in the future and ask students to categorize each item as living or non-living. This would lead to some speculation about what criteria must be met to qualify as "living." It might also lead to an idea that paper clips and beef jerky just don't belong together. There's something fundamentally different about them. Using foods as the "dead" materials was probably a mistake as well. I should have included wood, perhaps, or a preserved specimen. Again, I would leave it at the question stage here, and revisit the materials as the year goes by and ask students to refine their categories.
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