Tag Archives: Year 13

Miracle berries and my eureka moment

Sorry this is 24 hours late, but I’ve spent a very enjoyable day down at Streatham High School, taking a look round their new labs and discussing everything from iGCSE to KS3 science. It’s always so interested and useful to visit other science departments – we should do more of it.

Anyway, what shall I burble about this week? I was quite pleased with a new idea for introducing the Nervous System to Year 13. It was inspired by one of last year’s Year 13s who gave me some experience altering tablets as a thank you present. No, not what you’re thinking. It was pack of mberry miracle fruit tablets, available for £12.50 a pop at http://mymberry.co.uk/ and featured on the Graham Norton show https://www.youtube.com/watch?v=TJwuo2Y7KXs. The protein present, miraculin, causes a conformational change to your sweet receptors such that they bind to “sour” molecules. Result – a slice of lemon tastes like lemon sherbet. I got my Year 13s to suck on a slice of lemon, and then dissolve one tablet as per instructions on their tongue, and then try the lemon again. Sensational reaction! Then get them to explain it…  Along with all the revision of receptors and proteins, it’s a really neat way of showing that our perception of the world depends entirely on which part of our brain impulses get sent to…

What else? Well, I could tell you about the amazing fun I’m having with Year 7, or share the Year 12 practical investigation into osmotic inhibition of bacterial growth, or maybe the Year 9 Martian Biologist challenge – how can you tell the difference between Eleanor and a geranium? But I want to take a trip down memory lane and share my eureka teaching moment, when I suddenly realised what it was all about.

It was my second term at St Paul’s. I was due to start the Immune System with Year 12 and I was planning my standard kind of lesson – project image of macrophage, tell them about macrophage, give out picture of macrophage, label on board, draw picture of phagocytosis, etc etc. In other words, not a lesson, but a lecture, with no active learning, just information delivery. Students all passive. Me hoping to enthuse them with the inherent brilliance of macrophages and the sheer ebullience of my teaching personality. Ahem.

And then, clearing out the filing cabinet in my lab, I found an old sheet left behind by the retiring biology teacher who I had replaced. Here it is.

The Immune System

Natural Immunity

In mammals, non-specific or natural immunity operates partly through PHAGOCYTIC white blood cells (leucocytes).

  1. Observe a prepared slide of a blood smear. Using an Atlas of Histology and Biology textbooks to help you, identify and draw labelled diagrams of a phagocyte and a lymphocyte.

Add to your diagrams the mean diameter for each type of white blood cell (in mm) and a concise description of the cell’s appearance.

2)        Draw annotated diagrams to illustrate the mode of action of a phagocyte.

From where are phagocytes derived?

What are the two main types of phagocyte? How may they be distinguished?

It doesn’t look like much. No fancy formatting or sexy SEM images or even a joke or two. But the lack of frippery probably helped me “get it”. And it was so simple! I just needed to step away from the white board, put down the marker pen, and stop talking. I needed to tell the students as little as possible. Quite the opposite. I needed to let them find out for themselves. Make them do all the work. Base it around practical observation or investigation. Make it a journey of discovery. Make it active learning. My job was to guide and enable, not just tell them stuff. It came as a revelation, though in fairness to my brilliant PGCE teachers, it was basically what they had tried to tell us during the teacher training course.

So why hadn’t I got it earlier? The fear, I think, is in letting go, relinquishing control of the class, because as long as they’re looking at me and copying stuff off the board, I’m doing my job and it’s all nice and safe. The only down side is that, underneath all the busy scratching of pens, the students are bored and not actually learning anything….

Anyway, I’ve modified this leucocyte activity a bit now – in fact, I use a simplified version with Year 11 to put some practical activity into what can become a very theory heavy topic. I basically just give them the blood smear and a microscope. I tell them to find the blood cells (a challenge, coz they’re so small, but they can do it!), and then to find the ones with purple inside them. Draw them. Draw them large (half a page each). Label as much as you can. What’s the purple stuff? How can you tell? And so on. They love the challenge, the variety, the element of the unknown, the discovery…

Ugh. 8 period day tomorrow, just to round the week off nicely. Good news, I end it with Year 7 fully indulging their pyromaniac tendencies!

Ta ra.

Chemiosmosis and DNP; endosymbiosis

I am indebted to one of my colleagues for the following idea – I think it’s brilliant, many of you may already use it, or something similar, but it was new to me and sent me rushing to e-bay to purchase a World War 1 brass shell casing. Not got one in your department? You really should! I would put it up there with our Archaeopteryx fossil cast, our horse front leg bones and our giant brine shrimp tank as being an infallible source of student excitement and curiosity.

Year 13 again, I’m afraid. And as the attached powerpoint shows, it’s the story of the women working in munitions factories in WW1, and the fact that they showed dramatic weight loss (they also turned yellow and were called “canaries”, but that’s another tale). Why? Why? It’s a great example of how to open a lesson with a mystery – it grabs their attention, their imagination, and they get excited because they want to know the answer, they know they’re going to find out the answer, and, if you do it right, they get to work out the answer, which makes it even more satisfying.

So, one of the components of the explosives put into the shells was DNP, or di-nitrophenol. These days, it’s better known as an illegal weight loss pill, and there’s the tragic story of the young Leeds University student who died after taking it. But in the munitions factories it was just a weird and unexplained mystery. What does it do? It acts as a proton channel in the inner mitochondrial membrane. Now why would that make you lose weight? Their ability to explain this is a great test of their understanding of oxidative phosphorylation. You can also link it to brown fat, small babies, and hibernation. So, buy a shell! You can get them for around £10 to £15 on E-bay, and if nothing else, you get the satisfaction of explaining to the school accountant why you’re purchasing WW1 munitions…

…I’m also looking forward to being challenged over my purchase of a bottle of whisky for Year 7 Science. They’ve been studying separation techniques and I set them the challenge of working out how they would separate water and alcohol. As a consolation for not being allowed to actually do it, I’m taking them up to the school kitchen on Friday to teach them how to flambé bananas, which will be deliciously fun, but will also dramatically demonstrate why we don’t distil alcohol in the lab! Flambé bananas, I should add, are the signature dish of Bill, along with fluffy pancakes and slow barbecued lamb.

I’m afraid my idea for getting students to work out the Krebs Cycle flopped rather badly. That’ll teach me to never share an idea before I’ve tested it! Not only did it not work, they got terribly confused about everything and I had to wade in and do some heavy duty lifting to rescue things. It’s been modified now, and I’ll try it again next year, but much more carefully…

Nick and I are currently both trying to get a working model of chemiosmosis going, like the one Brian Cox showed on his programme I can’t remember the name of. Acid and water separated by some visking tubing with a couple of electrodes – a battery, basically – should be able to power a small motor. Mine didn’t even power a small LED and we ended up with about a litre of 0.1M HCl on the floor. Ahem. The origin of life needs a little more work…

One thing that does work is Endosymbiosis with Year 12. After a little background on the history of life and that crucial moment when complicated cells first appeared, I introduce them to Lynn Margulis (see attached sheet) and her idea. They then have to make some predictions about mitochondria based on this suggestion – and then find out if these predictions are true. It can take them a while to figure out what I mean by “prediction” but they will all suggest the presence of plasmids, ribosomes, binary fission, size/shape and susceptibility to antibiotics. The best of them will even predict that mitochondria should have two membranes, which is always a champagne moment.

Have a great week.


Munitions and DNP

TEM bacteria vis plant cells

Lynn Margulis and Endosymbiosis

Eating raw onion and turning on bacteria

Some people have been asking about the new A-levels and what we’re going to do. My preference, and the general feeling of the Curriculum Committee, is to abandon AS, free up the Year 12 summer for teaching (and having a year free of public exams!), and revel in all that extra time for practical work. But in the first year, when not all subjects have accredited specifications, we’ll still do AS for all subjects. I’m inclined to stay with OCR – better the devil you know – even if they can’t give me a clear answer on how my A2 students, who did their first set of PSAs on the field trip at the start of term, will not be disadvantaged with respect to all the students who do their PSAs after the 1st December when the mark schemes are released. C’est le dejeuner de le chien, if you ask me.

Anyway, back to the classroom. I’ve realised that I really really really really really like teaching Behaviour. We’re on to Insight Learning and after starting the lesson with the classic banana suspended from the ceiling and asking a student if they can get it down (disappointingly, in a girls school, they always get a sensible chair to stand on – back at SPS, you could always rely on the boy to give up after a desultory and ineffective leap, thereby enabling you to point out that he was definitively less intelligent than a chimpanzee), I then got the students to try and work out a number of wooden puzzles – this kind of thing http://www.theotherbranch.co.uk/item.php?pro=SPUZD. I let them work in pairs and give them about 4 or 5 minutes on each one.

Discussion then focuses on how they set about solving them – mostly, it’s trial and error. But the Indian Rope Trick is almost impossible to solve with trial and error, you have to have the insight, the moment of lateral clarity that makes you realise how to do it. Most students don’t get it within the lesson (I’ll be honest – it took me 2 days!), but at least one always does – and you then get to describe and explain how you worked it out (and if don’t know how to do it, I’m not telling!). Can chimps/monkeys do the same? I then show them the Capuchin monkey BBC film (“Monkey Puzzle” – extraordinary film of extraordinary animals) and set a homework asking them to try and figure out what types of behaviour are on display.

Elsewhere, Year 9 have been comparing the cells of onions and bananas. Both plant cells, but utterly different (if you’ve not done banana, just smear a tiny amount on a slide and stain with iodine – they are jam-packed with starch grains, are blobby and irregular, and have really thin cell walls). The girls draw and annotate both, and then use their observations to explain the differences between onions and bananas. I usually eat a raw onion for comic (but also illustrative!) effect. Homework is to write a letter from an angry baby to its parents, explaining why they shouldn’t be weaning it on to raw onion and why can’t it have nice squishy banana insteady? This always generates splendidly indignant babies and really differentiates those who “get it” and those who don’t. The drawings usually tend to be magnificent too. Lovely lesson because, apart from eating the onion, I don’t do much.

And my other Year 13s have been turning on E.coli in the Lac Operon investigation. If you don’t do this, you really should (I can send protocol details if you’re interested). It’s brilliant! Two culture broths of bacteria, one cultured in lactose, one cultured in glucose – and measure how quickly they break down the indicator ONPG to a yellow compound (ONPG is broken down by lactase aka beta-galactosidase). Not surprisingly, the lactose culture, rapidly turns yellow. But what I still find amazing is that in the course of the lesson, the glucose culture, introduced to lactose only at the start of the lesson, does turn very faintly yellow within the hour – the repressor is off and the gene is being expressed! The students find it very challenging to explain the differences and, again, it’s a great differentiator. But mainly it’s just really cool.

That’s me done for this week. Happy teaching!


TECHNICAL NOTES for lac operon

Intro to Lac Operon

Lac Operon

Year 13 – behave!

Dear Everyone,

Happy New Academic Year! Not that new, come to think of it, given that we’re already 3 weeks in. I would have re-started these weekly burblings earlier, but I’ve been swamped with such joyous things as UCAS references, Departmental Review meetings and the Year 13 Field Trip (actually, this was pretty joyous, even if nothing but giant slugs turned up in the Live Mammal Traps ). It’s also meant I’ve not had time to plan lessons properly, which has resulted in some Year 7s and 9s being rather short-changed – ugh, the kind of lessons that keep you awake at night. Still, I’ve never taught Year 7s before, and they are very nice. And very small.

The practical highlight so far has been Behavioural stuff with the Year 13s. I do enjoy putting the students in my Skinner Box. You need to borrow a couple of power packs/switches/bulbs from Physics but otherwise it’s a doddle. Arrange some chairs/benches in a square, put a switch/bulb on opposite sides, allocate two students to the two switch/bulb set ups (with a set of instructions each – attached – and a tube of smarties each) and then put the other students in, one by one and see what they do. Highly entertaining.

And taxes/kineses with maggots always amazes me by how brilliantly it works. No background theory – just straight in. Choice Choobs (© Burnett 2005) are easy to make – just a cardboard tube with a hole in the middle for introducing the maggots, and a bung. Get them to design the experiment, collect the data, analyse with Chi2, research the behaviour etc. Why is this adaptive? And so on.

Kineses are even easier – A3 paper, food dye, A3 sized tray for putting over the top. Dip a maggot in the dye, pop it on the middle of the paper and let it go. Record distance travelled and number of turns for 30-60 seconds. It produces wonderful, Jackson Pollock-esque images, and it works. The maggots go twice as fast in the light, and turn much more in the dark. Again, design, collect, analyse, research. These are really nice ways of revising basic skills (what type of graph? Where are the error bars? How do you analyse? Standard deviation?) and brilliant at really nailing experimental design/controls (how do you know your maggots don’t just head north?).

It also throws up some good statistics stuff – If 8 maggots out of 10 head to the dark, it’s not actually a significant effect, even though it looks like a clear preference. So what do you need to do?

That’s it for this week!


Skinner box operator instructions 1

Skinner box operator instructions 2