Back to Basics?

After going through a series of labs and projects over the last few weeks, I looked at the calendar and the curriculum and started to panic. Actually, the panic began when we spent 2 weeks on a digestive system project and got disappointing results on the regents test items relating to digestion. Now I am looking at a good deal of content that still needs to be covered, wondering how I can fit it all in. I've got most of the human bio topics still to address, plus ecology. I need to revisit evolution and genetics in the ecology unit and genetic engineering in the human bio section. That's about one calendar month for each of those major sections, then a couple weeks for regents review in June. That means any labs or projects we do need to be pretty tightly connected to the curriculum, limited in focus, and held to a pretty tight schedule. Looks like a lot of planning & thinking this weekend about how to do this without lecturing full-time for the next 2 months. At the moment my head is empty of ideas. I do have a bunch of sheep hearts lying around at school that we can dissect, so that's my fall-back lab for next week. Just need to find some interesting angle on it...

Results - Of Sorts

(Original Post on this Topic)

Good Technique:

This group did a nice job of keeping the detergents within their respective wells. The row of 3 smaller wells with virtually no change were for plain water (control, center well), Woolite (top of picture between 2 & 6), and ALL (lower portion of picture between 3 & 5). There are no enzymes in either of those two detergents.

Bad Technique

This group was either careless with the drops or jostled the petri dish around after drops were in place. The enzyme action is all over the place, and no useful data can be gathered.

However, of the 15 pairs in my class, we had about 12 with good results, and consistently Tide & Cheer worked best on the gelatin. Don't know if that translates into better cleaning action on real stains with real clothing, but I will encourage the student from yesterday to pursue that angle of investigation.

Science is a messy business

A fellow on a biology listserv just blasted cooperative learning and declared, without hesitation, that kids learn best when a teacher stands in front of the room and explains things to them. I hope we one day get past this "one true way to teach" false choice that so many educators are hung up on.

I wonder what his labs are like? I ask, because I have done a series of lab activities lately that were quite messy. Their original purpose was content based - I had a specific content objective that the lab was supposed to demonstrate. In each case, however, I have wound up teaching more about the scientific process than the content, because if I am honest with my students (which I ALWAYS am :>) and help them analyse the results and draw valid conclusions, then all the labs have been inconclusive - they do not conclusively demonstrate the content objective I started with.

Now, I think this is OK, or even pretty cool really. Students learn how difficult it is to control all the many variables that might influence the outcome of an investigation. They learn about the limitations of our measuring tools, about the importance of following a procedure precisely and consistently, the importance of repeated trials or large samples, or carefully recording results and calculating averages, e.g. They even get ideas for exit projects - either re-do one of the experiments and try to clean up some of the mess, or they think of other possible questions to investigate.

A concrete example. I found this series of activities on enzyme action. I am only using the one activity (Mello Jello) to test the effect of different detergents on dissolving the proteins in Jello - some of the detergents have enzymes, some don't:

The jello is prepared and poured into petri dishes, after adjusting the pH with sodium carbonate. Students use a straw to poke wells into the jello, then place a few drops of detergent solution into each of the wells. Tomorrow they will measure the change in the diameter of the wells after extracting the liquified jello with a pipette, presumably the ones with greater enzyme action will dissolve more of the gelatin. I've left out a lot of details, but it's a pretty nice set up, if it works. Of course the set up isn't that easy for 8th grade students. Some of them still have motor skill issues.

I didn't make it any easier for them. I made the gelatin a little too soft, so extracting the plug from the wells was a little difficult. Students had difficulty placing the drops in the wells with the detergent, spilling drops all over the place, probably contaminating some of the wells.

At the end of the period a student asked if she might be able to actually test detergents on clothing as an exit project. She made that connection herself, I didn't suggest it. I think it's a great idea if she pays close attention to the role of enzymes in the process and investigates the variables that affect the enzyme action, the organic molecules that the enzymes work best on, etc. I have seen this activity done poorly, where the only point was to do a product test and little or no science content was developed from it. But investigating enzyme specificity, pH, temperature, etc. seems like a valuable enterprise to me.

I have no idea what results we will get tomorrow. If the results are inconclusive, that's OK. Students will have learned some lessons about the scientific process and they are at least thinking about enzymes, meaning that they might actually be curious enough to pay attention when I have to "explain" it to them.

(Follow up post)

Disappointment

I went through the old regents exams and pulled out as many questions as I could about the digestive system for a test. There weren't that many that dealt exclusively with the digestive system - I could only find 8 questions out of 9 previous exams that I could use. There were a few of other questions that included the digestive system, but they were concerned with how the digestive system interacts with other body systems, so I couldn't use them for this particular test. I supplemented with a couple of questions from their textbook.

I was not pleased with the results. About 2/3 of students failed the test. I'm not sure where I went wrong. I think I asked the right kinds of questions for the research part of their projects, I had students perform presentations for the class on the digestive system, and in the end I went over all the details in a lecture/discussion format just to fill in any holes in their research and answer any lingering questions. I think I covered pretty well the content that was on the exam, without "teaching to the exam" so to speak. I did not teach with the actual exam questions in mind (i.e., give them practice questions that are paraphrased versions of the test questions), but I taught what the students would need to know in order to figure out the questions.

I could and probably will assign part of the blame to the students. They are simply not working as hard as they should be: Often they go through the motions, complete the assignment, but are not always fully engaged in the thinking part of the game. I have to say that on some level it bothers me that an "accelerated" class doesn't take more pride in their work or go beyond the minimum requirements of a task.

So now what do I do given these circumstances? If students aren't working hard enough, it is of course my job to bring them around. I may have to do what I've been loathe to do until now - start calling parents, sending home tests to be signed, all that nonsense that just reinforces the forced learning mentality - learn or else! But maybe that's just the nature of middle school students, even "high" achieving ones.

Digestive System Model: Photo

A rough idea of what the models looked like - balloons and construction paper. One of the students made the labels as an extra part of the model for hanging in the classroom - it's a nice touch and I wish I could incorporate it into the assignment, but with space being limited, and my room totally overused, it just isn't practical to have 16 models of digestive systems hanging around for other kids to come in my room and knock down.

From mouth to anus is about 25 feet, this model being roughly actual size.

Click here for previous post on this topic.

Guinea Pigs

Fridays are bad days to plan things like presentations, labs, new material, etc., and today was true to form. About a third of my class was out for some kind of musical performance and of course they weren't all from the same group, so several groups had missing members. I also left my camera at home, so no photos till Monday.

Actually a good thing it turns out. In spite of the missing persons, I decided to go ahead with a volunteer group for one presentation. I wanted to use them as guinea pigs, and told them as much when they volunteered, and gave them extra credit for going first - it's only fair since they will make a lot of mistakes that others will learn from (hopefully). And mistakes they did make. They were nervous, which reinforced the need to be prepared and have notes - it's hard to talk off the top of your head when your nervous. A few members of the group didn't know their stuff, so it gave me a chance to ask questions to let the others know what they would be expected to know. They also found out that there's a difference between being able to answer a teacher's questions about a topic and being able to explain something without prompts from the teacher. They didn't speak clearly or loudly enough. Some of them had poor body language, staring downward, fidgeting, etc. Some of the students seem to have learned more about teaching from sitcoms than from observing actual teachers: I don't think I've ever heard a real teacher say, "Now class, today we are going to learn about the digestive system..." - you have to imagine the kid putting on his mock friendly teacher face and reciting that line.

The other students rated the whole group' presentation based on the rubric. I rated individual students. In general they were a bit more generous than I was, which is OK. I will give a final score based on an average of the individual scores and the group scores.

The scale models aren't quite living up to my expectations. They all look pretty much the same: Once they saw a group using balloons for some of the parts, everyone wanted balloons. Making it a group project in class was part of the problem. In the future I would probably make it a homework assignment - they might get a little more creative if they have to look around the house for materials or go to the dollar store or grocery store and find something to work with. Class time was probably better spent preparing the presentations, working together on the research.

Final Parts of Digestive System Project

The basic strategy and introductory components of the project are in this post:

Is eating a "waste" of time?

I've elaborated on the details of the nutrient digestion, as well as a rough guide to the sizes of the various parts of the system to be used for the scale models. The whole project write-up can be found here:

A Journey Into the Digestive System & Beyond

and a set of guidelines and rubric for the presentations.

Guidelines & Rubric

The rubric is an adapted version of a generic presentation rubric from:

Teach-nology

Tomorrow are the presentations. I will post a picture or two and report on their performances.