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.


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


  • 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


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…


(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.


(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?


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


Send an impulse!




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.


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.


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.


So what?


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.


But an impulse to where?


A sweat gland, you great wally!


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.


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




Oi! Brain! Wake up!!!!


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


(sarcastically) Notice anything?


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


Notice anything else?


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


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


(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.


But we need sweat!

Sweat gland

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


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?!?!?


(very French: coughs meaningfully)


Who are you?


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




Releasez moi!




Releasez moi!


But I’m not holding onto you!


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!


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


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


No, I’m the Liver. Go away!


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


Oh go away. My receptors do not match yours.


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


(cheerfully squirting water into the bladder)



Stop excreting water!




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!


  1. (stops squirting water)



Is that it?


I’m afraid so.

Kidney (grumbles)

Very small part for me.


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


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

Heart and Lungs

We canna give her any more, cap’n!


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

Heart and Lungs

Thank heavens for that!


(shines torch at Heart and Lungs)

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


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


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


(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!


(meekly) Yes sir. Sorry sir.


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

Sweat gland

No sweat no sweat!


Er, yes.


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!


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).


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


(salutes) Insulin reporting for duty sir!


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


(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!


I’m the kidney! Sort out your receptors!


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


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


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




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


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!


Don’t you start again.


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.


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


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




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


Wake up! We’re overheating!

Sweat gland

Can’t do anything without a signal from the brain


Wake up!


(smugly) I said this would happen.


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


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


Ermm, movement? growth? ermmm, beer?


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


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



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.

Loadsa dough…

First week of the summer holidays, and I’ve been spending my mornings in the village primary school, offering some sciencey type lessons. I must admit, I was a bit wary – I was told that as part of the end of term arrangements, the children were being divided into four teams of 25 of mixed age. Please could I do four mornings with each group.


I find mixed ability hard enough – I don’t believe that it’s possible to consistently and successfully differentiate in a class any bigger than, say, 2, – but mixed ability AND mixed age? From 6 to 11? From some fairly severe SEN to precoscious semi-genius? Deliver a hands-on practical science lesson?

Yeah right.

So, what would you do?

Tricky, isn’t it?

I wanted it to be fun, I wanted it to be messy, I wanted it to be different to what they would normally do, I wanted it to be science. It also had to be safe and it had to somehow involve all the children in some way.

In the end, I opted for the dough rising at different temperatures investigation. I raided the lab for water baths, measuring cylinders, spatulas, beakers, glass rods, timers and balances. My technician had the inspired idea of throwing in 25 junior lab coats. I added yeast, flour and glucose.

I asked their regular teacher to divide them into mixed age teams of 4, each at a table with the relevant apparatus. I reasoned that if nothing else, they would enjoy handling real science apparatus, learn to take some measurements, and make a lot of mess. If they learned anything else along the way, that would be a bonus.

Setting up, the water baths, set to 45′, 35′ and 20′, were around the edge of the room. Each table had the following:

  • 3 x 100ml measuring cylinders
  • 3 x empty plastic beakers
  • 1 plastic beaker containing strong white flour
  • a glass rod
  • a tea spoon
  • a small saucer of dried yeast
  • a small  beaker of glucose
  • a stop clock

One of the most useful aspects, from my perspective, was teaching the same lesson 4 days in a row. The first day was OK, but I made lots of mistakes and had to completely rethink the lesson plan – there were too many blank faced children who clearly either weren’t engaged or just couldn’t follow what was going on. In short, I tried to explain everything in one go, and then let them get on with it. As you’ll see, this was way too big an ask for primary school children! They managed, but needed lots of support…

Incidentally, I think this is a key skill to being a successful teacher. Teachers stress over lesson observation, thinking that their performance is being assessed, but actually a good observer is just looking at the students. Are they interested? Are they involved? Are they doing lots of different things? Are they asking good questions?  Are they actually learning something, or are they just writing stuff down? There are teachers who seem blissfully ignorant that their pupils are bored out of their skulls. You have to be aware of the success or otherwise of your lesson if you want to improve. That, of course, makes an assumption. Again, I am amazed by the number of teachers who show no interest whatsoever in becoming better at their job…

I digress..

So, on the second day, I started by getting each team to decide on an identifying picture/cartoon/initials that they can draw on the top of their 3 measuring cylinders so they can tell which ones are theirs.

And then I ask one child in each team to pick up the balance.

And turn it on.

They then passed it on to the child on their left. That child had to…

…find an empty plastic beaker and put it on the balance.

I ask each table to report the weight of the beaker. The beaker/balance combo is then passed to the next child who…

presses the on-button again.

This, of course, tares the balance. I check that all the balances now read 0.0g, before the two items are passed on again. The next child has to…

add exactly 20g of flour to the empty beaker.

This is more challenging, and if this has landed on one of the younger students, the older ones pitch in and help. I have told them that the best scientists work as part of a team. But I’m pleased with how this approach is guaranteeing that all the children get to do something. Plus it’s training them how to carry out a procedure they’ll have to do twice more.

The beaker with 20g of flour is then passed on to the next child (who in a team of 4 would be the first one again). This one has to…

add 3 spatulas of yeast to the 20g of flour.

It’s fascinating watching how so many of them struggle with this. It re-emphasizes the point that practical work requires and develops all kinds of skills, which we can’t take for granted.

The beaker of flour and yeast is passed on and….

… one level teaspoon of sugar is added.

I now ask them to choose one member of their team who can both walk in a straight line whilst at the same time carrying a beaker of water. This lucky student gets to

collect half a beaker of water from the 35′ water bath

and take it back to their table. Now it’s time to introduce the measuring cylinders. Taking nothing for granted, I demonstrate the lines, the numbers, the intervals. They seem quite happy with this, so I ask them to…

measure out exactly 25ml of water from their beaker into the measuring cylinder.

Nice and easy, though never underestimate the ability of your students to devise ways of ballsing up a simple procedure. Because although they now have to…

pour the 25ml of warm water into the beaker with the 20g of flour, 3 spatulas of yeast and one teaspoon of sugar….

One cheerful group of boys pours it into the original stock beaker of flour. This only becomes apparent when they try to

use the glass rod to stir it all to a thick, runny paste

and merely succeed in creating a slightly damp floury lump.

And now, I announce, just in case they were finding this all a bit too easy, comes the really challenging bit! They have to…

pour their thick runny paste from the beaker into one of the measuring cylinders without any of it touching the sides….

Children of all ages love a challenge, and these are no different. The screwed up concentration on their faces is just a joy to behold. Of course, they all fail – though one girl was doing very well until her friend made her laugh and some dough smeared the side. But overall, it’s fine – they have enough paste in the bottom of the cylinder  for them to…

…measure the volume of dough in the measuring cylinder, write it down, and then transfer the cylinder to the 45′ water bath.

Phew! Now they just have to do it all again, twice, except that their second two cylinders will go into the 35′ and 20′ water baths respectively. And only then does the real fun start. Starting their stop clock, each team has to…

every 2 minutes, record the volume of dough in each measuring cylinder at the 3 different temperatures.

Initially, they are puzzled. What’s the point in this? But they quickly realise that the dough is rising! This has them scurrying back and forth in earnest. The primary school concept of a table is an interesting one, and we have to police the water baths as the measuring cylinders have an annoying habit of turning turtle, filling up with water, and losing all the crucial dough mix. But they take it very seriously, reading the volume carefully, and writing down the value with great aplomb, one girl writing “55ml EXACTLY”, just to emphasize the point. The excitement builds as dough in the 45’C measuring cylinders threatens to rise above the top and spill everywhere. Whose will rise the highest?

Eventually, it’s time to call a halt. I get them to all sit down with their measuring cylinders in front of them. So, they’ve done lots of measuring and used lots of different apparatus and developed all kinds of skills from team-work to spatula-work. But can they see the wood for the trees? What exactly have they shown?

This is really interesting. They don’t have the vocabulary or framework to make the link between the experimental design and what has happened in their measuring cylinders. But frame the question in a different way, and most of them seem to get the point:

What would be the worst place in your kitchen to leave dough to rise?

And this triggers some excellent questions from the older, brighter ones – but why? why do things happen faster at higher temperatures?

I’ve had positive feedback from parents, teachers and students, but I’ve got to be honest, though. I reckon that most of the students would say that the best thing about their science lesson was getting to wear the white lab coat…

That’s me done for the summer. Hope to be back in September.


Kill my babies, but let me eat meat!

Just a visual PS to the last post on energy flow through food chains.

Desk 1

Here’s the start of the game: there’s the pristine tropical island, with just a little corner of cultivation dedicated to growing enough plant food to sustain two people.

Desk 2

BUT…. they’ve decided they want to eat meat every day. Oh dear. The pristine wilderness is under threat!

Meanwhile, on vegetarian island…

Desk 3

…the population has doubled, but most of the island is still untouched.

Back on the isle of meat eaters, a doubling of the population has a more profound effect…

Desk 4

Animals at the top of the food chain are running out of space. The monkey eating eagles are endangered….

Veg-ville continues to cope reasonably well with population growth….

Desk 5

The population doubles again yet we’re still using less land than two people eating meat.

Compare this to the other island…

Desk 6

And here’s the really important question. Never mind the eagles, never mind the orang utans, never mind the vanished rainforest – what exactly are they going to do when the population increases again…?

As a sobering way to wrap up the topic, you could do worse than this…

Decisions, decisions…

Year 10 and Energy Flow Through Eco-systems. Not an obviously exciting lesson, I grant, but one with scope for some entertainingly confrontational role play. After all, it’s a tricky decision, give up eating meat, or kill your babies….

We spend a couple of lessons establishing the basics. The Leaf Litter practical – identifying, counting and weighing the crawly denizens of the detrivore community – after which I collect and collate all their data for them to draw accurate pyramids of numbers and biomass.

I also show them the Flamingo/Fish Eagle/Lake Bogoria clip from Life of Birds, to emphasize the spectacular fall in numbers as you move up the food chain, from algae (gazillions) to flamingoes (one million) to fish eagles ( a few hundred). David (Attenborough) provides the necessary descriptors.

Because this is a really interesting question – what’s going on here?

The following PowerPoint (@Burnett 2005) gives a simplified breakdown of how this all might be quantified as well as a beginner’s guide to why the energy stored in, say, grass, does not all get converted into rabbit.

Energy loss in food chains

In the past, I’ve tried to make this more rigorous using owl pellet dissection – can they use the contents of an owl pellet to calculate the area that a pair of barn owls would require?

Energy Flow from Voles to Barn Owls

But it’s over elaborate and I don’t think it worked very well – they miss the wood for the trees.

In any case, having provided the necessary background, ideas and theory, I’m more interested some of the broader implications of this inexorable law of energy transfers. In particular, how should it inform our choice of food and what we do with available land.

I’ve been playing around with ideas for how to explore this through role play for quite a few years. Again, none of my previous efforts have quite worked. So, for example, I came up with a kind of Monopoly version, where they had a laminated version of a map

island map for role play lesson

that they had to divide up into vegetable and meat cultivation, and then collect food calories (based on their allocation) from another student playing the part of Gaia.

Instructions for desert island survivor game

Having established this, I added more and more students to the island, playing the part of shipwreck survivors/African refugees/rivals from a local school, forcing them to reallocate land use if everyone was going to get sufficient calories per day. It was quite good fun (important note: even if a lesson fails, your students will forgive you if they can see that you were making an effort), but, again, it was over-elaborate and they spent so much time trying to do the calculations that they missed the key point of the exercise.

This year, however, I think I finally cracked it. See what you think.

I send all but six of the students out of the lab. These six form three pairs, each of which has a 70cm x 140cm desk. Each desk represents the island on which that pair have been ship-wrecked. There are no other survivors. The island is a lush, tropical paradise, awash with orang utans and parrots and butterflies and orchids. But they’ve got to eat, so they need to clear land for cultivation.

They have a collection of green and red bits of square card – 10cmx10cm, 20cmx20cm, and 40cm x 40cm.

The small green card represents the area of land that would provide enough plant based food for one person to survive. So with two of them on the island, they need a minimum of two small green cards. The rest of the island is left untouched. It’s an immediately visual impression of land use.

But they may not want to be entirely vegetarian. Most of them will want to include meat in their diet. Thing is, though, if they want to eat meat, one small red card represents the area of land that would support sufficient animals to eat meat only once every 10 days. So if they want to eat meat every day, they need to clear ten times as much land. Suddenly the island is looking rather different, the orang utans are feeling a bit constricted.

At this point I go and collect six more students and allocate two to each “island”. Look! Two more shipwreck survivors! And by an amazing coincidence, they’re old school friends! But what are they going to do about food?

The original students have to explain the game to the new students (peer to peer learning!) and then they all need to discuss and decide how they’re going to carve up the island. It’s an interesting contrast. One table is made up of vegetarians and their island is still largely pristine. Another is occupied by unapologetic carnivores and is covered in large red cards. But everyone is still able to enjoy their preferred diet, even if the orang utans are only just hanging on.

And then they have children. The remaining students are allocated, 3 per table, as the offspring of the original settlers. Obviously their babies are beautiful and adorable but, ahem, how are you going to feed them?

At this point, things get heated. Because based on the premise of the game, the island is not big enough to support seven people eating meat every day…. And so, with the brutal and decisive certainty of teenagers, faced with a choice of cutting back on their meat intake, or discarding their babies, the babies are thrown into the sea…

At this point, the interesting discussion can start. Why does it take so much more land to sustain a meat based diet? No, it’s not because the animals need space to move around – as one student suggests, it’s because you’re putting the energy in the vegetation through another organism before eating it. As 90% is going to be lost, you need 10x as much land.

This also explains why meat is so much more expensive than bread.

And it means how we decide to utilise farmland has profound ethical implications. Should we, for example, be clearing rainforest to grow cows/grow food for cows, just so rich people can eat beef every day?

And would any of them be willing to make any compromises to their diet (such as eating meat a few times a week, rather than every day) if it could contribute to conserving biodiversity, or using the same land to feed more people? Isn’t it immoral to eat meat in a world where so many people are starving?

If you like a feisty argument in your classroom, it works a treat!

Outline and questions here: Ship wrecked on a desert island energy flow June 2017 (1)