Tag Archives: learning by doing

Pressing none of the right buttons

So, last week I made reference to a Year 7 lesson on Animal Behaviour  that I thought people might like to try. Scanning back through previous posts, a kind of retro-burble, I notice that I had already mentioned this in passing as part of a Year 13 lesson. Given that the new A-level specification has completely removed any mention of Animal Behaviour as a Biological topic (why? what were they thinking?!!? absolute madness!!!!) I have simply moved all the wonderful practical activities down to KS3 so that our students get at least some exposure to this fascinating area of Biology.

Which brings us to Skinner Boxes. This follows rather neatly from the work they did with Hettie and Herbie (our hamsters) in their splendid cardboard mazes. After a brief review of the pros and cons of studying behaviour in a laboratory setting, I explain that today they will be working with a brand new animal. Can they guess what it is?

I leave most of the girls in the lab, under the supervisory gaze of our technician, and take two of them (pre-selected) into a neighbouring lab. Here I show them the “Skinner Box”, simply some tables rearranged to enclose a small, square area, with a button-operated bulb on each side (your Physics technician can run up a pair of these in 5 minutes or less). I explain to the two girls that they will be operating the Skinner box. This involves following the instructions on a series of experiments (Skinner box operator instructions 2 Skinner box operator instructions 1 where “rats” (i.e. Year 7 girls) are put, one at a time, into the box and allowed to explore their surroundings. The operators sit outside the box, opposite each other, with a box of Maltesers (to provide suitable rewards), and a long ruler (to provide “punishment”) each.

They quickly grasp what they’re meant to do. I tell them to keep the Maltesers out of sight, under the desk, and to not let anyone else read the instructions. For the first series of experiments, every “rat” will be a sample in Experiment 1 – the “rats” simply have to do is press the button and light up the bulb – if they manage this, they get a Malteser….

I go back next door. Have they guessed the animal yet? Mice! Woodlice! Guinea pigs! Rabbits! No, it’s a much simpler animal. Very basic instincts. Very readily available in a school setting. At this precise moment you are never more than, oooh, 50cm from one…. Oh, is it us? Bingo!

I tell them that they will play the part of experimental rats. That I’m going to take them one by one into my other laboratory and observe their behaviour for 15 seconds. That’s all. They’ve seen how hamsters behave in a strange setting – just pretend you’re a hamster. And I will be filming it all on the department i-pad.

And we’re off. Olivia, the first “rat” in, provides a textbook example.  She snuffles around inquisitively and, with seeming inevitability, presses a button. Flora (one of the Skinner Box operatives) dutifully delivers a Malteser. Olivia giggles with surprise and delight and immediately presses the button again. Voila! Another Malteser is provided. I quickly stop her because I don’t want the Maltesers to run out – she’s got the idea, she’s learned the association.

Experimental rats get to watch the other rats being tested – it’s partly the logistical difficulties of having yet another holding area, but mainly because I want them to see and enjoy what’s going on.

At this point, something rather surprising happens. The next 5 girls do nothing – literally, nothing. They stand there, all self-conscious and slightly giggly, some not even looking around, but absolutely refusing to risk doing anything in case it’s wrong. “What am I supposed to do?” some of them mouth at the other girls, but they are under strict instructions not to give any clues, and after 15 seconds I put them out of their misery (i.e. I stop the experiment – I don’t put them down humanely!).

Sofia, rat number 7, behaves just like Olivia (hurrah!) and then, joy of joy, in steps Maria who just decides that she will spend her 15 seconds spinning like a whirling dervish, her long blonde pony tail whirling behind her. “I’m dizzy….” she gurgles delightedly as she staggers out of the test area. By now, of course, every girl in the room now realises that they should have done and while feeling rather foolish and frustrated, they’re also enjoying seeing others miss the point.

By the end, only 5 out of 20 girls were sufficiently curious and lacking in anxiety to win some Maltesers. The rest just didn’t want to risk doing anything in case it turned out to be wrong, whatever that might mean. Where does this fear come from? Our education system? Our nationality? Can we blame Michael Gove? Whatever the reason, it makes for a good life lesson. Take a chance! Just do it! What’s the worst thing that can happen? You might win a Malteser!

Of course, having now all seen the kind of thing that’s going on, they’re all suitably prepped for the second round of experiments. This time I let everyone watch, because all the experiments are different. And now they are wonderfully imaginative and creative in their quest to get the right behaviour pattern. I particularly like the girl who just stands in the middle of the box and says, very quietly and politely, “Please can I have a Malteser?” Some girls find they are being prodded by a ruler – which continues until they press the button. And so on.

It makes for terrific discussion. How is this different to the maggot behaviour? Which is better for learning, reward or punishment? Should you revise with chocolate or electric shocks? And where are the real life examples of this kind of learning? This last takes them a while, but they eventually come up with learning what stinging nettles look like (could be a good comparison to start the exercise – demo lots of different leaves – which ones do they know), and the warning colours of bees and wasps.

Learning about Learning by doing – the only type there is.

And that’s nearly yer lot for this year. I’ll post one more burble next Wednesday, and then it’s the summer holidays. I, for one, can’t wait.

Strawberry and Coconut genetics

I forget who gave me the idea (I’m afraid I can’t claim it as my own), but if you’re currently extracting DNA from onions with fairy liquid (as my poor, weeping Year 12s used to do), then I’d recommend switching to strawberries and coconut shampoo as I did this year. Smells delicious, looks spectacular DSC_8169 (a little like you’ve liquidised a hamster), and produces prodigious quantities of what they’re happy to accept is DNA (though, truth to tell, most of the white goop is almost certainly pectin).

But onions (cheaper), strawberries (make sure you use coffee filter papers – the goop is too thick to go through standard lab filter paper) or frozen peas (frozen peas, along with onions, are the recommended vegetable of choice for the NCBE), there are ways of telling this story. I saw a teacher recently end the Year 12 Nucleic Acids topic with the DNA extraction exercise, reflecting their belief that practical work is a “just a bit of fun”, tagged on at the end if you’ve got time after the serious business of delivering immaculate notes and diagrams. By then, however, the end product comes as something of an anti-climax because they already know all about it. So what’s the point?DSC_8172

I prefer to do it like this…

Start with the DNA extraction. It’s fun, it’s messy, you can throw in some interesting questions on why you need to use detergent, 60’C water baths, protease and ice cold ethanol, and they end up with great goopy snot-like dribbles of “DNA” – several 1000km of the stuff if you reckon on 1m per cell.

Again, I should stress that if you want a higher percentage of real DNA, then onions or frozen peas are better, but given that we’re not going to sequence/amplify/carry out X-ray crystallography with the extracted material, I’m happy with my strawberries. The key learning point, apart from interpreting the extraction design, is that cells contains loads of this stuff, so it must have some really important function.

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OK, so there it is, DNA. What next? Well, there’s obviously loads of it, so it presumably has some importance to cells, but what exactly does it do and how exactly does it do it? They’re motivated to find out more so I send them off to think through some of the classic experiments that identified DNA as the molecule of inheritance.DNA experiments exercise

Next lesson, it’s time to explore the structure. You could just tell them, of course, but why not get them to work out the structure for themselves? I do no more than tell them that nucleic acids are polymers of nucleotides, and sketch the structure of a simplified nucleotide for them. They then do exactly what Watson and Crick did – cut out card models and try to fit them together.DNA model instructions DNA model parts (tip: make sure your sugar/phosphates are on a different colour card to your organic bases). Again, I must cite my sources – this is another of Bill’s typically brilliant creations.

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What makes this wonderful to watch is that even if they can remember A-T and C-G from (i)GCSE, they can now see why it has to be that pairing – A to T to 2, C to G to 3 (say it out loud), is my tip for remembering the number of hydrogen bonds.

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We then bring all the nucleotides together in a large class molecule…

DSC_8202…and I play them the clip from DNAi where Jim Watson recalls the moment when they saw it  – the morning of February 28th, 1953. I tell them he got a Nobel prize for doing what they’ve just done – if you make your students feel brilliant, then they will do brilliant things.

We go back to the model and discuss it. What can they see? They can see that, to put it together, the two strands have to run anti-parallel. They can see the symmetry that the purine/pyrimidine pairing gives. It’s easy to point out the 3’ 5’ direction. I mention the footnote to the original Nature paper – “It has not escaped our notice that the specific pairing we have postulated immediately suggests a possible copying mechanism for the genetic material”

Can they see it as well? Yes they can! That base pairing means each half is a template for the other may be half remembered from (i)GCSE, though not with the clarity provided here. The hydrogen bonds which provide such a ready means of unzipping the molecule are also starkly obvious. Their next homework will be interpreting the design and results of Meselson and Stahls’ beautiful experiment. DNA Replication Meselson Stahl prep Meselson Stahl experiments

And so on. We hang our model from the ceiling and attempt to make it 3D and helical. It comes in very useful when explaining PCR to the Year 13s.

In the next lesson, when I finally give them a simplified diagram to label, DNA basic structure the detail they recall and include is fantastic. Because they figured it all out for themselves while I made a coffee and fed the hamsters.

Bupples and Benedicts

Back to burbles of a strictly biological nature this week, and a recent idea that passed quality control with Year 7.

So, what do you think of Benedict’s Test for reducing sugars?

To be honest, I’ve always regarded it a pretty boring part of any Biology course. Oh, it’s wonderfully colourful, and the students always enjoy the chance to get out the Bunsen burners, but given the intoxicating wealth of mind-boggling Biology available to anyone tasked with writing a specification, it’s odd that it repeatedly survives the cut, while Immunology (to take just one example) gets repeatedly hacked to the bone and beyond.

Now, one of my main projects this year is to completely re-write the Year 7 Scheme of Work. I want to move away from a course where factual material is delivered in vast, turgid chunks, to lessons that encourage curiosity about the natural world, asking interesting questions and answering them through experimental investigation – you know, something a bit like Science. As far as possible, as with all my teaching, I want them to find things out for themselves.

Being a general science course, I spent the autumn term working on Chemistry (Purification) and Physics (Energy) which has been a lot of fun, and I’ve learned loads as these are both well outside my area of expertise (particularly Physics, which I gave up when I was 14). But now we’re finally on to the first Biology topic and I’m feeling a lot more zonally comfortable. The theme is Cells and Human Reproduction and I’m basing it largely on apples and hamsters. Wonderful things, apples….

So, opening lesson, do they like apples? They nearly all do. Why? Because they’re crunchy! Well, lots of things are crunchy (bricks, gravel, celery, cockroaches) – there must be something else going on. Because they’re sweet! Aha, why are they sweet? Because they contain sugar! Good hypothesis! But how do you know? Ermmm….because sugar is sweet? Maybe, but lots of things might make something sweet, how do they know that it’s specifically sugar that makes apples sweet? Blank looks.

Right, working in pairs, they have 4 small beakers, one of sugar (glucose), one of distilled water, one of apple juice, and one with a mysterious blue liquid. Pausing only to demonstrate safe use of a simple water bath, I tell them to use the above to prove that apple juice contains sugar.

The blue liquid is, of course, Benedict’s reagent, but they don’t need to know that. And I deliberately don’t tell them that it’s a test for sugar, otherwise the whole learning outcome of the lesson is negated. What are they going to do?

I’ve praised curiosity and the value of testing ideas empirically since September, so they’re very happy to try lots of things. Again, it’s one of those lessons where you’ve got to be quite hands on, moving quickly between the pairs to hear their ideas and head the more ridiculous ones off at the pass. Some of them think they should separate the sugar from the apple juice by evaporation (echoes of the Purification topic) so I point out that I haven’t provided an evaporating dish – the water bath is for heating. Plus even if they did this, how would they know that the separated powder was sugar?

Many of them just shovel all the ingredients into a test tube and heat it. Oh the excitement! It goes brick red! Wow! Fantastic! Well done! What does that show? Ermmmm…. And at this point they really start to think.

So they heat the blue liquid with apple juice. It goes brick red! What does that show? Ermmmm….

So they heat the blue liquid on its own. Good. What explanation are you eliminating? Still doesn’t show its sugar, of course….

So they heat the blue liquid with sugar. And so on.

Nobody’s mentioned controls, fair tests, but they demonstrate that Ben Goldacre is absolutely right – children intuitively understand the principles of a scientific experiment.

By the end of the lesson, they’ve taught themselves Benedict’s test and, based on the follow up homework which I’ve just finished marking, the vast majority understand the importance of eliminating other possible explanations with controls. And they feel really pleased with themselves because they’ve done it all themselves. Better still, in the next lesson, they can all recall what they did and why they did it.

More on apples to follow – they are a fabulous biological teaching tool!

Have a good week.

Post Burble

Why bupples in the title…? It’s how my eldest son pronounced “apple” when he was 2 years old. I encourage my students to do the same.