Monthly Archives: November 2014

Fun with Fungi

OK, I take it back; WordPress is great – I’m just being more than unusually incompetent in trying to figure it out. I think (touch wood) that I’m getting the hang of it…

And golly, the burblings are being read all over the world! OK, so 1 hit in Australia (hello, Melissa!) and one hit in America (hello, Julie!) doesn’t quite equate to global domination, but it’s a start….

Back to the plot.

iGCSE classification.

Ugh.

Doesn’t get much duller than having to learn the defining features of the 5 Kingdoms. It’s rather like conceding to Rutherford that, yes, all science is either Physics or stamp-collecting, a grim throwback to the days when all Biology could do was describe and classify things, because it was all far too complicated/small to actually understand. It’s a challenge, I think, to make this topic interesting.

The first thing I do is break it all up; schemes of work don’t have to follow the exact order of the specification, and it’s a good tactic to disperse the duller stuff across the terms and years. So the Year 9s can compare plant and animal cells under the microscope and observe some of the obvious differences – a homework where a plant and animal cell meet in a bar and have an argument as to which is the superior cell gets them to use the information. Comparing a student to a geranium from the perspective of an alien scientist draws out the other points of comparison.

Bacteria and protoctists? Save them until Year 11 when they can meet them in the context of disease.

But Year 10 is when they meet yeast as they learn about respiration so it seems a sensible time to learn about yeasty things. It starts easily enough with a picture of a mushroom. What’s this? A mushroom. Well done. How would you classify it? It’s a bit like a plant – sessile, multi-cellular – but it can’t be a plant with that chitin cell wall and the lack of chlorophyll. Hang on, lack of chlorophyll? That means it must be…. anyone remember the term?…. heterotrophic! But how can you be heterotrophic if you can’t run after your food (which is the whole point of not having a cell wall!)?

This is where it gets hard. A mycelium of hyphae? A who? A what? I can still remember that awful feeling of blank incomprehension that usually swept over me in French lessons, but reared itself in Biology when I first encountered these terms. Without context, without function, it’s just meaningless vocabulary. So they need to see it and understand it.

Here are three ideas, not mutually exclusive. One, suggested by Bill, is to carve up a pumpkin about 4 days before the lesson. As he says, nothing does fungal growth quite like a pumpkin. You get to pull it apart in front of the students to reveal the great fluffy mass within the oozing, pulpy ex-pumpkin. Yum. Another, discovered serendipitously, is to just leave an agarose gel in the fridge for 3 weeks. The inevitable fungal spores grow into glorious 3D stars, captured within the gel, as the hyphae snake out into the gel. They are startlingly beautiful.

Or (and this is my personal preference), you can start by asking them if they’re hungry (always a good question for teenagers). Yes? Right, come over here! Lots of food over here! They cluster eagerly around the big box – but are rather disappointed when I reach in and pull out a toilet roll. No? No-one wants to eat a toilet roll? But why not? It’s full of energy! Burn a few sheets to demonstrate presence of energy in toilet paper. Not tempted? Hmmm. But what’s paper made of? Wood. Which comes from? Trees. Which are? Plants. And plants are made of? Plant cells. So which part of a plant cell do you think paper is made of? The cell wall. Which is made of? Cellulose. Aha, what’s cellulose made of? They probably don’t know, so point them at the helpful cellulose models made by your Year 12s (next week for details on this!). Cellulose is just hundreds of glucoses joined together. And glucose is a? Sugar.

So, why can’t you eat toilet rolls?

And here’s the chance to revise digestion, and enzymes, and enzyme theory.

So, even if we did eat a toilet roll, it would have little nutritional benefit because we can’t digest it, we don’t have the right enzymes. But I’m going to introduce them to an organism that can…

At this point they stuff their own toilet roll with a fungal spore mix from http://www.ncbe.reading.ac.uk/NCBE/MATERIALS/MICROBIOLOGY/oyster.html.  This then goes on the back burner as we do a few more respiration experiments, or set up the fast plant experiments, or whatever. A few weeks later, we fish them out and take a look.

OK, a word of warning. It’s a pretty strong pong! Think rotten Stilton with a strong overtone of even more rotten Camembert. But! What can they see? How would they describe it? The toilet roll is full of wispy fluffy hairs. What’s going on? And here you can talk about hyphae and extra-cellular digestion and how the whole fluffy mass is the mycelium. Words to describe what they can see, a function to fit to the new vocabulary, it all makes sense.

A few weeks later, the toilet rolls sprout an amazing crop of oyster mushrooms, and we go up to the kitchens to fry them in butter and garlic. And isn’t it amazing??? I mean, just think about it!!!! Here’s an organism that can convert a toilet roll into oyster mushrooms! Saprophotastic!

Even Harry Potter can’t do that.

Sylvia Plath mushroom poem can be found here http://genius.com/Sylvia-plath-mushrooms-annotated with some nice pictures of fungi… would make a lovely addition to the lesson

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Malteser and sardine salad

Hello!

I must say that I’m not overly impressed with WordPress. For one thing, you’ve probably noticed an annoying box at the top of my home page. No idea how it got there, no idea how to get rid of it. Grrrr. And then, when I tried to form a Word Cloud to help people find certain topics or resources, it took me hours to achieve absolutely nothing. Double grrrr.

Anyway, it’s achieving its main function of hosting my burbles and linking them to specific resources. And it’s free, so I really shouldn’t grumble.

I’m going to stick with Year 9s this week. Bill’s flipped diffusion worked brilliantly, as did the follow up, and they can now describe and explain diffusion based largely on what they have observed and deduced. My one modification for next year is to include a classic “cheat” that I’m sure we’re all guilty of – the warm/cold diffusion rate was different, but not as much as you might expect. So next year I’ll be providing 0.1M cold acid to compare with the 1M warm acid (though, of course, they will be told that the concentrations are equal). I’d love to hear other examples of this kind of educational economy with the truth – it would make a good post!

Next up, we’re going to review why diffusion is important. I like to use this Powerpoint sardine simpler version – another Bill creation – for them to observe and interpret. What’s going on here? It’s very neat. Notice, incidentally, how creative you can be with this much maligned software, once you’ve learned some of the basic animation features. Notice, too, the complete lack of notes! There’s a few questions to go with this, linking back to the microscope work they’ve done on Protoctists a few weeks back meet Mr Paramecium .

I then ask for a volunteer. They might be hesitant as they’re not sure what to expect, but I reassure them. I tell them they’re an amoeba. I remind them that they need a constant supply of oxygen. I produce a box of maltesers. Each malteser represents oxygen. We imagine that they need one oxygen every 3 seconds to survive. I then shovel maltesers into them at the rate of around 1 every 3 seconds. All good fun. The idea is that a single celled organism can rely on simple diffusion from the environment for its oxygen demands.

I then ask for 10 volunteers. No hesitancy now! I line them up in a row, with the original amoeba at the far end. Now they’re cells in a multi-cellular organism. Same rules apply. They each need a malteser every 3 seconds. Can they still rely on diffusion from the outside world? It’s great – the maltesers never get past the 2nd or 3rd “cell” – so they immediately see the problem – it’s too slow, and the oxygen all gets used up anyway.

Back to the powerpoint! Look at the sardine and the idea of an oxygen transport system. And then they all dissect a sardine (or mackerel, or herring, or whatever comes off the slab!). The excitement over this activity is astonishing! I like to set little challenges, so as well as getting them to cut out the gills and dip them in water/observe under the binocular microscope, I encourage them to try and find the swim bladder without bursting it, to find the heart, to not reduce the fish itself to a pile of mangled sushi… Labelling and annotating this diagram Why a Sardine cannot rely on Diffusion alone for its oxygen supply can always come later…

Right, I’ve got a train to catch. More next week!

Year 9 diffusion

Good morning!

My Year 9s have finished their animal/plant cell introduction to iGCSE with an exercise where they pretend to be Martian scientists who have taken two samples of life from Earth – a geranium and a student – and are trying to figure out whether they’re just slightly different versions of the same thing, or whether they are fundamentally different. It’s a fun way of getting them to work out the key classification points, without actually telling them.

They’re now into diffusion as a logical extension of this – what do cells need? And how do they get these things? Always keen to try something new, I started this year with Bill’s exercise (attached). Like all great ideas, it’s deceptively simple. But look at it in a bit more detail, you start to see not only why is it fun, engaging and challenging, but also why it works so well as a learning activity. Note the lack of preamble, no “today we’re going to study diffusion…” introduction, just straight into a “do this and figure it out” approach.

It’s fun – they love the little cubes (though they were disappointed to learn about their lack of edibility) and are genuinely intrigued by the colour change. They can explain this at one level – the challenge is to push them beyond the “acid is moving into the cube” description, to something more rigorous about particles. But they quickly see the effect of concentration and by the end of the activity they’ve basically worked out the definition of diffusion for themselves, and seen/measured that it happens more quickly if the difference in concentration is greater.

I’m following this up with an adaptation of my olde introduction to diffusion (attached). As well as making lots of different sized cells, they’re also going to compare diffusion rates at two different temperatures. Again, they work it all out for themselves. The questions are for homework.

Next week I’ll tell you how I move this on to multi-cellular organisms and maltesers…

Have a great week/weekend!

Paul

1LT1 – Flipped diffusion in jelly blocks 1

Acid bath and agar blobs with temperature NOV 2014

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.