Tag Archives: nervous system

Mapping Retinas

You can’t really go wrong with eyes. Oh, unless a student starts feeling queasy with the eyeball dissection. But it’s one of those Slam Dunk Open Goal Shoo In topics that you would have to work really hard at to make dull. So the following is just throwing some random ideas out there which you might consider (if you don’t already do them).

I start by making the entire class stare at a huge red heart projected on to the board for two minutes.


Then immediately switch to a white screen. They love this – it’s weird, it’s unexpected, it’s slightly unsettling, and it stimulates the obvious question – what the…?

So then we map their retinas.


This is a resource I found in an age old file 15 years ago or more, so it’s not original, but I love it. Keeps them usefully occupied for 45 minutes or so and all you need is some A3 paper, sellotape, meter rules and two pen lids, one red, one green. I’ve adapted it a bit and added a homework exercise with interpretive questions to help them understand the wonderful maps that they produce…


Once they’ve figured that out, you can go back to the red heart trick and ask them to explain it.

And if you are dissecting eyeballs, do make sure you see how high the lenses will bounce…


Sheep Dash and Water update

Last week I wrote about a last minute lesson plan emerging from a fog of exhaustion and panic (a Groundhog moment from the first year of teaching where every single lesson is like that!). I’m pleased to report that the lesson in question was a great success, the Year 8s enjoyed the activity and could almost immediately understand and explain the difference between their two sets of results ( see attached exercise here Sheep Dash experiment). I also made use of the class skeleton and a spare Chromebook to talk them through the sequence of events that take place from the moment that the sheep makesits dash, to their successfully(or not!) clicking the dart gun.

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I’m following that up with a simplified version of Bill’s marvellous Brain Injury exercise (also see last year) which is an excellent example of how you can turn what could be a dull lesson in information delivery into a lesson of learning and discovery. It’s based on the fact that most of what we know about brain function was originally deduced from linking an injury to a specific region of the brain (stroke being the classic example), to the symptoms that follow. Students “damage” localised areas of the brain and are told the resulting symptom(s) – they then try to infer what that part of the brain does. (brain injuries) It’s also a great illustration of the potential of Powerpoint, where the direction of the lesson is determined by the students’ choices, not by the linear construction of the slideshow. Have a go! It’s strangely addictive, even when you know the answers….

The new Year 12s are adjusting to life at A-level. I talked last Year (22nd October) on my introduction to Water (which is also my introduction to the A-level course). One girl this year got the HIJKLMNO(5) clue in less than a second (literally!) which given that I normally expect this to take 5-10 minutes, rather threw my lesson plan. But once the water circus and the water properties homework is out of the way, I then go back to the importance of the solvent properties, particularly the idea that metabolic reactions take place in solution. I talk about the origins of life. I talk about Miller and Urey and show them this (amino acids intro it’s another one of Bill’s splendid animated Powerpoints), stressing the idea that in certain conditions, complex organic molecules can arise spontaneously out of simple ones. But there’s a problem….

I herd them all into a corner of the lab. You’re all complex organic molecules, I say, amino acids and nucleotides and stuff, all in solution, pouring out of that cold vent in the ocean floor. The rest of the lab is the big wide ancient ocean, 3.5 billion years ago. If you could only bump into each other, we could get life kick started! But what happens….?

It’s lovely. They all drift apart, sub-consciously (perhaps) recalling Year 9 lessons on Diffusion, until they’re evenly spread throughout the “ocean”. I stop them. What’s happened???? Why can’t you bump into each other???? Oh no! Life is never going to happen… unless…. What else must we have? They instantly see the need for some kind of enclosing structure to stop them diffusing irrevocably apart. What do we call that enclosing structure? A cell membrane! Aha! And what property, I say, must a cell membrane emphatically NOT have????

This last question usually requires a few seconds thought…. Someone might suggest “permeability”, which is fine – I praise the answer and then park it for a future lesson – but what else? Given what they’ve just done, what property must the membrane NOT have? Yep, that’s right, it must not be soluble in water. Which means it must be made out of something…? Hydrophobic. Can they think of any common hydrophobic organic molecules….?

This launches us into Lipid chemistry and the background to cell membranes, one of my favourite topics on this or any other specification.

I structure it this way because I like the story, the logical sequence (rather than sticking water into a random lesson half way through the course), and the evolutionary context. I like the way it stresses the primary role of a membrane – which helps when we come on to compartmentalisation – and I always like getting them up out of their chairs and doing something, even if it’s just role-playing an amino acid in an ancient ocean….

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.