Origins

I’ve burbled on this topic before, but only briefly, tucking it at the end of a piece principally about World War 1 Shell Casings and the link to deadly diet drug, DNP…. I want to revisit it, primarily to describe in more detail the lesson, how I structure it, why it works, and use it as an example of how you can turn a non-practical lesson into a process of inquiry and discovery.

See what you think. Better still, let me know what you think!

Year 12. We’ve just about finished Cell Ultra-structure, they’re about to do a homework on Electron Microscopes. I show them this picture…

embryo

As ever, Powerpoint for me is a way of projecting thought-provoking images or interactive animations. I never use it to deliver notes – the phrase “Death by Powerpoint” exists for a reason…

So, what is this?

And immediately, they’re engaged. It’s a mystery! A puzzle! They’re all thinking and all have some kind of suggestion. I also use it as a way of encouraging involvement – have a go! what’s the worst thing that can happen? you might be wrong! but at least you tried…

After a round or two of interesting ideas, I start providing clues and someone usually guesses, correctly, that it’s a human embryo on the end of a pin.

I follow this up with another picture of a human embryo, just a bit closer in.

embryo 1

OK, key question, what did this start life as?

Yes, that’s right, a zygote. A single cell. Formed when a sperm and egg fuse…

But that egg, where did that come from?

From the mother. Of course.

And how did that individual start life? Yes, exactly, another zygote! Also formed from a sperm and an egg…

And that egg, where did that come from…?

We start a regress, back through the generation, through ma to grandma to great grandma and beyond.

If we keep going, I ask, where do we eventually get to?

To apes, someone say! Well, OK, yes, a common ancestor of us and apes to be strictly accurate, but no, much further… how far can you go?

They get it. The very first cell… This year, one of them can actually refer to LUCA (Last Universal Common Ancestor).

OK, all very cool and a bit mind boggling and stuff, but how would they describe that very very early cell, in just one word?

We try out a few suggestions before agreeing on “Simple”. This makes sense. Simple things evolve before complicated things. But what does that actually imply? What would this very early, very simple cell, have looked like?

We can’t know, of course, but as a way of stimulating discussion, I show them this:

bacterium.jpg

What do they notice about this cell, particularly compared to the cells they’ve been studying?

That’s right – it’s got no nucleus, no mitochondria, no rough endoplasmic reticulum, none of the complicated internal structures of the rat liver cell that has cropped up so frequently on their interpretive electron micrographs.

So if this isn’t LUCA, what is it? What very simple cells are still among us? Again, they generally get this – it’s a bacterium.

I then contrast it with a more familiar A-level cell…

plant cell

… from which they can cheerfully pick out half a dozen different clearly visible structures.

Which brings us neatly to the key question of the lesson. How did life on earth go from this…

bacterium

to this…

plant cell                           ?

At this point, I construct a time line on the board, starting with the origin of the Earth 4.5 billion years ago and sign posting it with the key relevant events along with the way (origin of life, 3.5 billion years ago, origin of complicated cells, 1.5 billion years ago, origin of modern humans, 200,000 years ago…). I then use this to add a few notes about the types of cell involved – the simple ones, the Prokaryotes, and what this means, and then the complicated ones, from which all multi-cellular life evolved, the Eukaryotes.

This allows us all to draw breath, before we return to the key question…

How?????

We bat a few ideas around. I drop a few visual hints (mainly be juxtaposing the two images and asking them what the bacterium resembles). And eventually someone has the necessary brainwave – did one of them start living inside the other?

Bingo! Endosymbiosis! Lynne Margulis’ brilliant idea that was, as things so often are, ridiculed and rejected….

Lynn Margulis and Endosymbiosis

And finally we can get on to the main exercise where I get them to figure it out for themselves (see attachment above). For if mitochondria used to be free-living bacteria, then perhaps we can make some predictions about what we might expect mitochondria to be like.

I put them into groups of 4 and get them to jot down all the things they already know about bacteria, without looking anything up in their books or their smartphones. Their list will eventually include at least some of the following…

  • they’re really small
  • they have plasmids
  • they reproduce through binary fission
  • they have ribosomes
  • we kill them with antibiotics

From this, I get them to come up with simple 5 predictions about mitochondria, again without looking anything up. Things like, “if mitochondria used to be bacteria, then they should have ribosomes…”

Once they have a list of 5, I let them check their predictions. And lo and behold, they’re right! There is evidence for endosymbiosis, even if it happened over a billion years ago. And they figured it out.

They’re convinced. They’re happy. It’s a successful lesson.

But now contrast it with an alternative lesson plan, perhaps put into a Powerpoint presentation… it might go something like…

“Today we are going to learn about endosymbiosis. Endosymbiosis is the theory that cell structures like mitochondria used to be free-living bacteria. Evidence for this theory comes in the similarities between the two. See the following list…”

It’s the self-evaluation every teacher should carry out before every single lesson plan – am I teaching? Or am I delivering information? The difference, at every level, could not be greater…

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Russian roulette…

Just a quickie this week….

It’s Year 10 and the grim effects of smoking. The biology is interesting, though I must admit I prefer to celebrate the power of data to do good things (Richard Doll) and get them thinking about experimental design (how to show a causal link between smoking and cancer?). The following exercise is designed to cover these learning outcomes and doesn’t need much comment from me (though do look at the wonderful quote from James 1st/6th!).

Smoking and Epidemiology and Richard Doll November 2017

But how to convey the sense of genetic Russian roulette that is random mutation?

For this, I came up with the following interactive Powerpoint…

Random mutations in DNA interactive

The first slide just introduces chromosomes and we have a very basic chat about genetics and the idea of coded information.

chromosomes

A mutation, I explain, is just a random change to that information – the key point is, it could occur anywhere….

The second slide indicates 22 loci (the blue circles).

chromosomes 2

I ask a student to pick a blue circle, a locus. Any one they like. Clicking on the blue circle will, 21 times out of 23, take them to a slide saying:

Silent mutation

No effect no person

Clicking on the smiley face takes them back to the second slide, and the locus they selected magically disappears. We talk about the idea of silent mutations. Another student picks another circle, with, one hopes, the same effect.

But at some point, somebody will choose the bottom circle of the two on chromosome 7. Clicking on this circle takes them to this message:

Mutation to onco-gene

Uncontrolled cell division

Tumour

So I hope they take home the idea of random mutations and that smoking is like playing Russian roulette with your genes, but also the idea that the more you smoke, the more you increase that risk.

Short and sweet – let me know what you think!

Festive Viral Fun

So, what kind of teacher are you?

When Year 11 start Infectious Disease, I always get them to build Jolly Christmas Viruses. There’s quite a variety of cut and stick models easily accessible on-line…

virus model

…and if you photocopy them on to lots of different coloured card and lay in industrial supplies of glue and glitter and pipe-cleaners, you can’t really go wrong.

I do insist that every virus be different. I show them a clip from Secret Life of the Cell (about 15 minutes in) where we see an adeno-virus gain access to the cell using its antigen and a cell receptor (this kind of hinting at the glorious complexity of A-level Biology is all part of my retention and recruitment plan).

And then I put on some salsa music and let them get on with it for an hour…

When they’re done, they attach a bit of cotton thread and we dangle them from the lab ceiling, where they quietly drizzle glitter on innocent students for the rest of the year…

IMG_2241

Here’s a not-particularly-special bacteriophage in mid-dangle.

I’ve worked with teachers who utterly fail to see the point of this lesson. It addresses no learning outcomes, it delivers no information, it utterly fails to tick a single learning objective on the specification, it uses up valuable Copy The Notes From The Powerpoint time…. I think they panic because they feel out of control – the students are working autonomously, and this is an uncomfortable feeling if you’re not used to it.

But…

It’s fun.

It’s different.

It’s memorable.

They will do wonderful things – one student produced a virus with a little portrait of Justin Bieber at the end of each antigen – the virus that causes Bieber Fever….

It gets them asking all kinds of interesting and relevant questions.

Because how can something so tiny (a virus to a football is the same as a football to the planet Earth…) and so simple (bad news wrapped in protein) make you ill? Discussion of rabies and smallpox and herpes and AIDS all follow naturally.

Which leads nicely to Immunology. Try my simplified animated Powerpoint as an introduction to Clonal Selection and Expansion…

Immune response

 

Blow their minds…

Sometimes you just have to amaze them. Go in and say, “have you seen the news today???? They’ve only gone and detected gravitational waves from the collision of two neutron stars!!!! Isn’t that amazing???? What? Neutron stars? Oh, stars that collapsed but didn’t quite become black holes. All the space in atoms crushed down so that a teaspoon of star has the same mass as all of humanity…. And two of them collided! Caused a kilo-nova! Equivalent of 1000 supernovas!!!!! Isn’t that mindblowing?!?!?!? And that’s where all the gold and platinum in the universe is made!!!!! So my wedding ring is made from stuff formed by two colliding neutron stars!!!!”

Of course, being biological burblings, I prefer, where possible, to use biological examples.

Such as some of the experiments emerging from epidemiology.

Heard the one about the mouse?

Conditioned with cherry blossom and electric shocks (almost sounds like a treatment for hair – wonder if it would help it re-grow?). So it learns to associate the smell of cherry blossom with an electric shock, and starts trembling with fear just with the smell of the blossom. Pure Pavlov.

But then let it breed – a nice break from electric shock therapy. And then expose the offspring to the scent of cherry blossom….

The offspring tremble with fear even though they have a)never been exposed to cherry blossom before and b)never had an electric shock in their lives.

That’s incredible. How does it work? We don’t know! But that’s where and why science is exciting, pushing at the frontiers of knowledge and trying to understand the universe better.

Heard the one about the other mouse?

Stick it in a cage with a bigger mouse where there’s nowhere to hide. The smaller mouse gets bullied. Becomes fearful and runty. Doesn’t grow. Stressed and pathetic.

But then pop it in a cage with a female and let it breed. Again, makes a nice change for it.

The offspring are all fearful, runty, stunted, stressed pathetic mice.

Seems like more evidence of epigenetic effects.

BUT!!!! – now you can talk about the importance of experimental design and rigorous controls.

Repeat the experiment, but instead of letting the bullied mouse breed, extract its sperm (don’t ask how) and artificially inseminate the female.

Guess what – when not exposed to Mr Runty himself, the offspring are all perfectly normal. So not epigenetic, but still pretty bloody amazing – the female can somehow adjust her level of maternal investment based on the apparent quality of the male.

How??????

I think this kind of thing is so important. Because if you can’t get excited about your subject, why on earth should you expect your students to? And keeping up to date with the latest developments provides a constant supply of amazing stories to inspire them with.

Role-playing Homeostasis

As regular burble fans will know, I use lots of role play in my lessons. Students become molecules, baboons, ship-wrecked survivors, blood-letting physicians and so on. In this lesson, which covers the whole of the Homeostasis topic, they have a wide variety of roles. With a synoptic set of homework questions to follow. Note the props!

The downloadable script is here: Homeostasis Play anonymous version October 2017

(note that you can choose the name of a specific student by using Word replace function to replace Student with a name...)

but for ease of reading, I’ve also included it below.

Student’s Big Day Out

an adventure in the Homeostatic Wonderland of Student’s body

Dramatis personae

  • Student’s brain
  • Student’s liver
  • Student’s pancreas
  • A sweat gland in Student’s skin
  • Student’s kidneys
  • Glucose molecules
  • Insulin
  • ADH
  • Student’s muscles
  • An Enzyme
  • Student
  • Student’s teacher
  • Heart and Lungs

Props

  • Model: heart, lungs, brain, liver, kidney
  • Large beaker – red water
  • Large beaker – yellow water
  • 3 x distilled water bottles
  • Can of Coke
  • Potato
  • Thermometer
  • Torch
  • Weights

Student

You join us at an exciting point in my school day. I’m about to walk down the corridor to my favourite lesson of the week, Biology. Can my body cope with the extraordinary demands that this exercise will present? Or will I die? Let’s find out.

Student’s muscles (pumping iron)

Typical. We do nothing all day long and suddenly we have to work really hard. Contract, relax, contract, relax, contract, relax. Where’s the oxygen? Where’s the glucose? It’s not easy being a muscle, I can tell you, especially Student’s muscle. Phew, it’s getting a bit hot in here…

Enzyme

(very camp) Tell me about it! Here I am, controlling the rate of respiration, producing ATP, basically helping this boy/girl here do her work, and it’s warming up. Doesn’t he/she know I might denature? Just look at my active site! (displays active site) Very sensitive, me. What will he/she do without respiration? I’m the main character in this play, and don’t you forget it.

Brain

(yawns). Hmmmm? Whassup? Whassgoingon? Oh, right, it’s the end of Maths. Mmm,  and now I seem to have made a decision to walk along a corridor. Better check on the blood temperature. (dips thermometer into blood). Blimey! It’s gone up 0.1˚C! Time for a bit of action on the cooling front. Ermmm, what do I do? Errm, damn, if only I’d been paying attention in that fantastic Biology lesson, I’d know the answer. Help! It’s gone up 0.2˚C! This could get critical. What do I do?

Enzyme

I’m OK for the moment, but don’t push your luck. 0.2˚C I ask you.

Liver

Send an impulse!

Brain

What?

Liver

Send an impulse! Cor, call yourself a brain? I’ve seen bigger brains in an intestinal nematode. No question who the most important organ round here is.

Brain

I agree. No question at all. Look at how complex I am. Look at all the things I control and monitor. I’m responsible for all his emotions and memory and everything! Definitely THE most important organ.

Liver

Pah, if I wasn’t here to store the glycogen, heat the blood and break down toxins, you wouldn’t last 5 minutes. I’m the centre of metabolic activity, me, so less of the superiority complex. Every animal has a liver. Very few have a big brain. Check out any Year 8 student.

Brain

So what?

Liver

Well, put it this way. If I wasn’t around to break down the alcohol in people’s bloodstream on a Friday night, they would be terminally dead before Saturday morning. Anyway, stop prevaricating and send a flaming impulse! We’re all getting warm down here.

Brain

But an impulse to where?

Liver

A sweat gland, you great wally!

Brain

Oh yeah, a sweat gland. (shines torch at sweat gland).

Sweat Gland

An impulse! Hurrah! Let’s get sweaty! (squirts water over Student). Lucky I’m here. All this water will evaporate off his/her skin and he/she will lose heat as a result. How cool is that?!?! (continues to squirt Student)

Enzyme (grudgingly)
Hmmm. Things do seem to be cooling down a bit. That’s nice. But hey, not too much cooling! I’m very sensitive, me.

Liver

As she keeps saying. Hope that stupid brain is on the job. We seem to be losing a lot of water.

Brain

(snores)

Kidney

Oi! Brain! Wake up!!!!

Brain

Huh? What now? Honestly, if it’s not one thing it’s another.

Liver

(sarcastically) Notice anything?

Brain

(defensively). Er, no. (looks at thermometer). Er, yes! We’re back to ideal blood temperature! Hurrah for me!

Kidneys

Notice anything else?

Brain

What do you take me for? A biologist? Though now you mention it, this blood seems a bit sticky.

Liver

Ta da! Come on, get your osmotic pressure sensor out!

Brain

(guilty) Oops! (dips potato in blood and looks at it) Oh no! Now we’re losing water too fast! (looks at thermometer). But we’re still heating up! (shines torch at sweat gland who squirts Student)

Sweat gland

Still sweating! No sweat, sir.

Brain

But we need sweat!

Sweat gland

That’s what I mean! It’s no sweat to keep sweating.

Brain

Oh, right. (looks at potato). But the blood is getting too concentrated! If the blood gets too concentrated, something horrible will happen. And if I had only done the theory on the Osmosis project back in Year 9, I’d know what!  Help! What do I do now?!?!?

ADH

(very French: coughs meaningfully)

Brain

Who are you?

ADH

Who am I? who am I? I am zee famous ADH, that’s who. Antee, Die-yoo-rettic Hormone.

Brain

So?

ADH

Releasez moi!

Brain

What?

ADH

Releasez moi!

Brain

But I’m not holding onto you!

ADH

Look, you English fool, your father is an ‘amster and your mother smells of elderberries. I shall say zis only once. Send an impulse to zee pituitary gland which is just in front of you. And it will release me into ze bloodstream. Do it! Before your little cells shrivel up and make you even less capable of rational thought than you already are, and I shall taunt you once again!

Brain

OK OK OK, here goes. (shines torch at ADH)

ADH

Close enough! I am free! (floats along in the blood stream knocks on liver) Allo? Is zis de Kidney?

Liver

No, I’m the Liver. Go away!

ADH

Ooops, sorry, I shall try again. (bumps into Pancreas). Allo? Are YOU ze Kidney?

Pancreas

Oh go away. My receptors do not match yours.

ADH

Let’s try again. ( bumps into Kidney) Oi, Kidney!

Kidney

(cheerfully squirting water into the bladder)

What?

ADH

Stop excreting water!

Kidney

Why?

ADH

Coz I tell you to, you dozy organ. We’re losing too much water in the sweat and at this rate he/she’ll be dead from dehydration. Stop excreting water!

Kidney

  1. (stops squirting water)

(pause)

Kidney

Is that it?

ADH

I’m afraid so.

Kidney (grumbles)

Very small part for me.

Muscle

Oxygen! Give me more oxygen! And get rid of this damn carbon dioxide!!!!

Brain

(shines torch at Heart and Lungs). Come on, chaps! Work harder!

Heart and Lungs

We canna give her any more, cap’n!

Muscle

Phew! We’ve stopped! He/She must have reached the classroom.

Heart and Lungs

Thank heavens for that!

Brain

(shines torch at Heart and Lungs)

Calm down, sort out the oxygen debt, and then return to resting levels. Right, I’m thirsty.

ADH

Of course you are. That’s something else I do.

Brain

Hmm? Is the teacher watching? Quick! Let’s drink some coke! (Student swigs some Coke).

Teacher

(thunders) Student’s surname!! Are you mad! You are deliberately imbibing the drink of the devil! You will suffer tooth rot, mood swings, caffeine addiction and Type 2 diabetes! Put it away this instant!

Student

(meekly) Yes sir. Sorry sir.

Brain

(shines torch at sweat gland) You can stop too.

Sweat gland

No sweat no sweat!

Brain

Er, yes.

Pancreas

Never mind the sweat! It’s too late! The stomach is full of glucose molecules and we’re going to have big problems here very, very soon!

Liver

Yes, everyone knows that you only have a teaspoon of glucose in your blood at any moment. Student’s just drunk something that’s 30 times more concentrated! What’s going to happen?!?!? (picks on non-actor to answer the question).

Pancreas

Exactly! Luckily, I know what to do. Insulin!

Insulin

(salutes) Insulin reporting for duty sir!

Pancreas

Ah, Insulin, loyal and trusty hormone. You must hurry to the Liver. Travel in the bloodstream. You know what you must do.

Insulin

(salutes) Yes sir! (hurries off in bloodstream, passing Glucose molecules that are entering from intestine). Cor, look at all this glucose! If this gets much worse, the blood will get too concentrated, and Student will lapse into a coma. Would anyone notice? Hmmmm. But we must still avert the danger! Watch me go!

(reaches Kidney)

Oi, Liver!

Kidney

I’m the kidney! Sort out your receptors!

Insulin

Ooops, sorry. I’ll try again. (reaches Liver) Oi, Liver!

Liver

Oh, look, a little hormone. What can I do for you, little hormone?

Insulin

Less of the patronising nonsense, sunshine. You’ve got a job. See all this glucose?

Liver

Yes.

Insulin

Get it out of the blood! Take it into your cells and do something with it. But do it quickly!

Liver

Righty ho. (starts grabbing glucose). In you come, all of you, that’s it, through the membrane, out of the blood. Naughty glucose! See the problem that brain causes? If it hadn’t decided to drink that Coke, none of this would have happened!

Brain

Don’t you start again.

Liver

Oh don’t mind me. I’m just a liver. You’re the suicidal idiot who dumps all this rubbish on the body. I’m just the poor sap who has to deal with it. (sotto voce) She’d have been much better as a gut nematode. (louder). Right, you glucose molecules, line up! Attention! I’m going to put you into storage. But I can’t store you as glucose because you’ll affect my osmotic balance. Here, link arms. (glucose molecules link arms). Good! Now you’re a molecule of glycogen, and you can stay there until we need you.

Enzyme

What happened to the cooling mechanism? It’s still too hot.

Liver

Must be the school’s lack of air conditioning. Get the brain to sort it. Brain! Oh brain!

Brain

(snores)

Kidney

Oh great. He’s dozed off. What shall we do now?

Enzyme

Wake up! We’re overheating!

Sweat gland

Can’t do anything without a signal from the brain

Muscle

Wake up!

Liver

(smugly) I said this would happen.

Enzyme

I’m melting!!!!! (active site changes shape)

Muscle

Help! If he can’t work, the body can’t respire!  Check out the 7 life processes!

Kidney

Ermm, movement? growth? ermmm, beer?

Muscle

RESPIRATION, you dolt! All LIVING things respire. And we’ve stopped respiring!!!

Liver

Bother. There goes respiration. We’re going to die!!!!!

 

THE END

Hydrophobia rules

I structure the Year 12 SoW to build a foundation of important fundamental principles as quickly as possible. So we start with water, making interesting and topical links to the possibility of life on exo-planets, or Europa, and establishing all those vital properties that make it essential for Life As We Know It.

I then focus in on its role as a solvent. How can we tell if something is going to be soluble in water? We build the important vocabulary and concepts and I get them to work out whether any given molecule is likely to be water-soluble.

But is it soluble…

I get them to think of oxygen as the child at a party who won’t share its electrons nicely, so that not only is water polar, but so are -OH groups. And we explore why lipids cannot dissolve – they bring nothing to the water party, and quickly get jostled out of the way so that the water molecules can resume their endless round of speed dating, meeting new and exciting molecules every nano-second.

We then have an imaginative role play where I get them to imagine the very first origins of life on earth, a little corner at the bottom of the ocean where some organic molecules spontaneously form and can start reacting becaue they are soluble, and are therefore free to move and collide. The students are the organic  molecules, standing in the corner of the lab (the deep sea vent), but what will happen?

This takes them a while to figure out. Go on, I urge, what will you do? In solution, in the deep sea? Sure enough, they start to drift apart, diffusing to the far corners of the lab. Why is this a problem for kick-starting life? They get it – they’re too far apart to ever collide. Life will never get beyond the odd nucleotide.

So what do we need? We discuss the concept of a barrier, something that hold these molecules in one place, to prevent them diffusing into oblivion, and allow the very first reactions of life to take hold. And I ask them, what property must this barrier NOT HAVE??? This takes them a little longer as they’re not quite sure what I’m asking. But then the light dawns – any barrier intended to prevent water-soluble molecules diffusing away into the big blue sea MUST NOT BE SOLUBLE ITSELF. In other words, it must be hydrophobic. Can they think, off hand, of any potential hydrophobic molecule that might serve as the basis for this barrier, this, for want of a better word, MEMBRANE?

We look at lipids, figure out why a simple lipid can’t work, introduce the idea of a phospho-lipid, and try drawing diagrams of how they would interact with water, and how you could arrange them so that could associate happily with water while yet remaining insoluble. There’s a lovely lightbulb moment when they figure out the phospho-lipid bi-layer.

Still with me?

OK, so now they can start to work out some of the properties of this MEMBRANE thing. It’s a really nice example of how even a largely theoretical topic can be turned into a journey of discovery, where students figure things out for themselves, rather than just telling them what’s going on.

I set them this exercise.

Movement across cell membranes

A whole load of molecules/ions that must cross membranes if cells are to survive – but can they cross a phospholipid bi-layer? It’s back to the very first principles of water and solubility. If it’s soluble in water it must be hydrophilic, but the membrane itself is hydrophobic. So can water cross it? No. Can ions cross it? No! Can glucose cross it? No, no and thrice over no!!!!

I start introducing bigger ideas. Using this animated PP as an illustration.

channel proteins

Na+ cannot cross the membrane, it will be repelled by the hydrophobic core, and yet it must cross. Your entire nervous system depends on it. Every thought you have, every thing you feel and see and hear and believe is based on Na+ crossing cell membranes. Cl- cannot cross membranes. But it must. If Cl- doesn’t cross membranes you have cystic fibrosis and your lungs fill up with mucus and you are very ill. Even water itself, by definition, cannot cross a hydrophobic barrier!!! And yet clearly it must, not just for simple rehydration purposes, but the whole basis of osmo-regulation in the kidney is built on the water permeability of cells in the collecting duct.

So it must be more complicated than this…. Can they suggest anything?

The suggestions come in, slowly, tentatively, until someone eventually (and they always do) wonders whether there could be another pathway through the membrane?

What, like this? A click on the PP and a channel protein inserts itself. And slide by slide, we build up the properties of these rather wonderful structures. Specific, gated, facilitative of diffusion… It’s a wonderful moment as they start to understand the first basic principles of selective permeability. And it’s why Membranes are one of my favourite topics at A-level.

Bloody Year 10s…

Here’s how I introduced a new topic at the start of the autumn term for my bright and eager Year 10 classes this year.

It’s an interactive Powerpoint – no, wait! – nothing complicated, just a click and reveal quiz as they choose the blocks based on number or colour.

Blood eating animals introduction

Simple question to start with, can they name any of the organisms?

In fact, why don’t you try it? See how many you get…

(brief pause while eager reader attempts quiz)

How did you get on? Here’s what Year 10s generally make of it.

They all get mosquito and vampire bat. Most of them will get flea and remember it as the Robert Hooke drawing from their introduction to microscopes in Year 7. The leech is sometimes identified as a slug, or a flatworm, but a little prompting gets them there. They often call the tick a spider – for valid reasons! – but usually get Tick, VG! (joke). Bed bugs is a lottery. I point them to the clues if they get stuck. Very few get beyond “bird” for the red-billed oxpecker, though students I have taught in previous years sometimes remember that this is my PhD species… and hardly any ever get the Masai warrior.

Next question – what do all these organisms have in common? The Masai and the oxpecker throw them, because they were thinking, “they all eat blood!” but this is new.

Yet they’re absolutely right. These are all organisms that subsist entirely or largely on a diet of blood.

I take time out to explain the Masai traditional lifestyle and how they use their cattle as a source of blood and milk. This year, I made up some stage blood and asked if anyone was brave enough to try the Masai diet. One brave girl tasted the blood/milk cocktail – and exclaimed, “that’s not blood!!!” (stage blood is syrup, corn starch and food colouring).

But, key question: what does this tell you about blood?

They instantly see that blood provides a perfect balanced diet. So it must contain what?

We discuss the types of carbohydrate, protein and lipids that appear in blood and their function. So many proteins! So many functions! This takes us neatly into the four main functions of blood as a whole (thanks to Bill Burnett for the following Powerpoint review)…

Year 10 Circulation intro

… and its overall structure….

…setting them up nicely for a look at their own blood in the next lesson.