Unit 5 and the benefits of "lab first"

I'll admit, I may have strayed from the central theme of modeling instruction-- "the model."  I'm still struggling with the concept of the "model" for biology.  Our models just end up being, well, notes.  I realize I haven't even been using the word "model" this semester as I did in the earlier units.  I should try to improve upon that and re-incorporate the concept of the model.

But I have become an ardent fan of the "lab first" style of teaching science.  I don't think I'll ever go back to a traditional lecture/lab structure.  One of many teachers' criticisms of labs is that the students often miss the point.  I frequently saw this myself:  you'd cover a topic like osmosis and diffusion, then go into the lab supposedly to reinforce the concepts.  The problem was the students often couldn't put two and two together and just ended up going through the motions.  I'd frequently skip discussing the lab in lieu of just having them answer questions about the lab, which they often answered poorly.

The benefits of switching to lab first are innumerable.  Two of the biggest are that it forces you to actually discuss the lab results and it gives the students something tangible to make connections with.  The only downside is that I occasionally get a snarky comment from a student who thinks he/she knows it all ("I don't get how this is supposed to show us ______.").  But even those are rare and have greatly decreased.

For example, this week I have been covering cell membranes and transport.  Hypertonic, Hypotonic, and Isotonic are terms students traditionally struggle with.  So earlier this week, we made rubber eggs (instead of the potato lab) that were ready for today:

From left to right, eggs soaked in distilled water, a mixture of corn syrup and water, and corn syrup alone

The students were able to talk out what happened to the eggs and form a conclusion based on what they already learned about osmosis.  All I had to do was introduce the new terms.  The concept of "hypertonic" is a million types easier for a student to grasp when they are quite literally grasping a deflated egg in their hand.  And when they got confused, I just reminded them to think about the eggs.

I gave my classes Unit 5 Exercise 2 today (I replaced "potato" with "egg").  Several of my students told me it was "easy."  That's nice to hear for a change!

Unit 4 Wrap Up

Remnants of our photosynthesis lab

You know that feeling when everything hits the fan?  That's been my past couple weeks.

I thought Cellular Respiration and Photosynthesis went well.  My test results from last week said otherwise.  Looking back, Unit 4 was WAY too much material and way too diverse of material.  I was aware of this while I was teaching, but I didn't realize quite how significantly it impacted my students until the test.  Grades were still good, but class averages were lower than usual.

In my darling standard biology class, the 50:50 split was worse than ever.  Half the class had high As, two Cs, and the remaining students failed and failed badly.  For those students who failed, they temporarily lost their lab privileges and in lieu of lab completed an open notes re-test.  The strategy seemed to help, re-test grades were much improved, and I was able to work one on one with many of them while the other students were working on a dialysis tubing lab.  I realized two things working with the students individually:  1) just how overwhelming this unit was, and 2) the average sophomore in high school knows NOTHING about plants.  I mean nothing at all.  Multiple students said that my class was the first time that had EVER heard that plants make their own food.  I'm not sure I've ever encountered that before... but without any prior knowledge to help make connections, the process of "photosynthesis" was a billion times harder for them.  Who woulda thunk it.

In the meantime, we've started Unit 5 The Cell.  I've made some modifications due to time.  We did an intro to the microscope and looked at plant and cheek cells.  Then we did some diffusion/osmosis experiments, including perfume in air, food coloring in water, and glucose/starch in dialysis tubing.

Out of all my classes, only ONE group included "air" particles in their diagram.  Obviously this wasn't the group.

Dialysis tubing with glucose/starch solution placed in a beaker of DI water and Lugol's Iodine.  Fun fact- glucose didn't diffuse through the tubing as it should have this time around. I inadvertently reinforced a misconception in all my students' minds.

Not the strongest conclusion ever... 

We also set up a "rubber egg" osmosis lab instead of the potato lab included in the teacher notes.  Meh, I wasn't feeling the potato set up.

We have, count 'em, less than FIVE more weeks to get through:  transcription/translation/protein synthesis, enzymes, mitosis, meiosis, and all of genetics.  Ouch.  Let the panic attack begin.

Unit 4 Reflections: Cellular Respiration Continued

Cellular Respiration-- not one of the most interesting things we get to teach as biology teachers.  I mean honestly, raise your hand if you actually care about the Krebs Cycle?  I sure don't.  And I've never totally understood why or how it's important for the state to test students on whether more ATP is produced in Glycolysis or Oxidative Phosphorylation.  But I digress...

We held our board meetings on yesterday's activities.  Here's how I set it up:

Yesterday, I had written a generic definition of "cellular respiration" on the board that they copied down between activities.  I didn't talk about it at all, I just told them that they were modeling "cellular respiration" with the ball and stick models.

Today, I asked them to refer back to that definition and create a white board with a verbal, mathematical, and diagram explanation of that definition of cellular respiration using evidence from the two lab activities.  They were confused and stumped, but surprisingly game and receptive to the challenge.

Prior to WBing, we had recapped about the "ingredients" in each of the balloons, and even hypothesized a little about each of their role in inflation of the balloon.  They had some really interesting theories they were all sure of-- the warm water caused the molecules in the balloon to move faster, causing expansion of the balloon.  The warm water dissolved the sugar faster so it could "react" with the yeast.  The yeast was a catalyst.  The yeast produced oxygen.  I just kept telling everyone those were interesting theories.

Most groups used the chemical equation for mathematical (I kinda tipped them off on that), and diagrams of the balloons or models were easy enough-- but they were stumped on the verbal.

In each class, I spend a lot of time with about 50% of the groups firing questions at them, and basically ignored the other groups.  I tried to focus on the "weaker" and more uncertain groups.  They all had the same questions:  "We don't know what you want us to do.  These labs had nothing to do with each other."

In my rapid firing, we focused on the glucose and the chemical equation.  Glucose was one of the reactants in the model of cellular respiration.  Was glucose involved in the balloon lab at all?  (Yes, it could be derived from the sugar)  Was anything else in the chemical equation also found in the balloons?  Where did the oxygen come from?  What evidence did you have CO2 may have been produced?  Does it seem plausible that this reaction could have happened in the balloon?  So if I leave sugar sitting on the counter, it will turn in to CO2 and water, right?  (Umm... no...)  Then why did the balloon inflate?  What else was in the balloon?  Re-read that definition-- why did we add the yeast?  What did we discuss about yeast earlier?

And then about that time, each group had the most rewarding OH MY GOD I GET IT light bulb moments.  :) :) :) :)

My only regret is that these groups were SO excited they "got it" and while many of their peers still didn't... and they WANTED to blurt it out in the board meetings.  The groups I spent time with were waving their hands in the air the entire board meeting, wanting to talk... and I reeeeeally wanted to let them show off their new found knowledge.  But... I also wanted everyone else to have that same epiphany.

We then did a terribly boring textbook "active reading" session about ATP.  Great way to cap that good discussion, huh?  But there was a reason.  On Monday, we had a district teacher inservice with a speaker who I will not name.  He was not one of the better educational speakers I have ever heard.  While he made some good points, overall I thought he was extremely antiquated and out of touch with today's students and schools.  His big emphasis was on more reading and writing-- less doing, more reading, writing, and note-taking.  Kids today aren't college prepared because they can't read textbooks and they can't write papers (I do agree with that part).  One of his criticisms of science teachers was that we "do" too much and pride ourselves on not even using a textbook (um, guilty).  I disagree with him that you should only read and write about science, but I do think I am doing my students a disservice if they never have to trudge through a science textbook at least a few times.  While we do read in class, our reading is usually article-based.  The speaker gave me a good reminder to step it up with the textbooks.  Reading about ATP was a perfect opportunity-- I can think of no topic more dull to practice reading dull stuff.

Each student received a photocopy of the 4 pages out of the text on ATP and highlighters.  We read the first few paragraphs together and discussed how to identify the important points... then I set them free with a guiding question (what provides energy for the cell) and told them to keep highlighting what seemed important.  Afterwards, they were to write a paragraph reflection of the reading that answered the guiding question.  We discussed our paragraphs afterwards, which was extremely insightful.  While many students did fine and wrote great summaries, here is a direct quote from a bright honors student with a 98 class average:  "I didn't understand a single thing I read."  Hmmm.  While I don't think we will be reading the textbook every day, I definitely do think I need to throw it in more frequently.

Unit 4 Reflections: Macromolecules and Cellular Respiration

...and we're back from our lovely 10 day fall break today.  And jumped right in with cellular respiration.

I've had to add a lot to unit 4.  Not only did I toss in all the ecology standards, but I also needed to cover the biological macromolecules in more depth than the AMTA lesson plan suggested.

The AMTA lesson plan has students researching proteins, carbohydrates, and lipids on their own with a few guiding questions, then jumping in to comparative dissections.  My state EOC exam tests pretty darn heavily on proteins, carbohydrates, and lipids-- especially the structures and how to determine their presence in the laboratory.  Plus, our biology teachers here usually save our dissection for the last days of class after the EOC exam, since dissection and internal anatomy are not tested.  So, I ended up skipping the dissections (for now) and spending more time on the macromolecules.

Having the students research the macromolecules with guiding questions was futile.  First of all, when given the option of textbook or Google, students always go to Google.  I don't think that is necessarily a bad thing, as textbooks are becoming utilized less and less, even at the collegiate level.  But... as sophomores in high school, students can be easily led astray by misinformation online.  Especially on a topic like this, which is loaded with intimidating new vocabulary like "monosaccharide" or "polypeptide."  The whiteboard results I got, to put it simply, were really bad.  I still think it was a good activity, but I will definitely limit them to the textbook next time to avoid wasting nearly an entire class period.  Instead of dissections, we then went to the lab to practice testing for macromolecules.

Sudan IV testing for lipids

The AMTA curriculum kicks off cellular respiration with a yeast lab using Vernier Probes to measure % O2 and CO2.  The total amount of Vernier equipment my school owns:  0.  We got nothin'.  So it was back to the drawing board again.

What I decided to do was combine a yeast balloon lab with the next activity in the lesson plan, which is modeling cellular respiration with ball and stick models.  First, students created balloons with yeast and differing amounts of warm water, sugar, and air:

They measure initial diameter, set their balloons aside, while I briefly introduced them to the term "cellular respiration."  They were instructed to make a model of a glucose molecule and 6 diatomic oxygen molecules:

A glucose and a pile of O2 - not bad for students who have never taken chemistry, let alone organic chemistry. I wasn't going to split hairs on the position of the bonds in the glucose at this point. Maybe I should have.

They were then told a chemical reaction occurred between the molecules and they needed to create two new molecules.  I asked them to think about waste products, respiration, and had to prod some groups on ideas... but all of them eventually came up with CO2 and H2O.  They were then challenged to figure out how many CO2 and H2O molecules this reaction would create.  Once they were complete, they had to create an equation for cellular respiration.

Then we revisited our balloons and determined change in diameter.

We didn't get much time to discuss or create a consensus.  My plan tomorrow is to hold a board meeting with a verbal, mathematical, and diagrammatic representation of cellular respiration based on the results of the two activities.  And I guess I'll see what I get!