Osmosis – The Solution to a Concentration Problem

Throughout my career I have had the privilege to observe a large volume of science lessons.  Two key stage 3 and key stage 4 topics fill me with a sense of dread in those lessons – osmosis and evolution (perhaps a future blog).  The dread stems from my experience that many teachers, with the best intentions, overcomplicate their teaching and confuse the students – all in the name of keeping it simple.  I have had the conversation below with new and experienced teachers, subject specialists and non-specialists.  I probably should have written this a long time ago.

Before the solution, first the problem

The phrase “osmosis is the movement of water from high concentration to low concentration through a partially-permeable membrane” is the problem, specifically “water from high concentration to low concentration”.  Before we go further, yes most exam boards will accept this as a definition of osmosis (but only if worded very carefully and only as an accept… rather than the main marking point) and yes some GCSE biology textbooks use that definition word for word.  Shame on the exam boards and shame on the publishers.

Why do teachers phrase it this way?  Some will see it in the textbooks and mark schemes and just go with it.  Many phrase it this way because they have just taught diffusion (movement of particles from high concentration to low concentration) and are building on that knowledge in their osmosis lesson.  Most key stage 4 schemes do not explicitly include the vocabulary of solutions (solute, solvent, solution, dilute, concentrated) so teachers use the idea of concentration of water as a shortcut to avoid reviewing these terms.

Why is it a problem?  Because it makes absolutely zero sense and requires teachers to invent a new, non-specification definition of concentration.

Why doesn’t it make sense?  When you dissolve a solute in water, you do not change the number of water molecules, therefore you do not change the “concentration” of water molecules.  The volume of the solution does not change (and definitely doesn’t decrease), therefore you do not change the concentration of water molecules.  The “concentration of water” remains constant.  If the “concentration of water” is the same on both sides of the partially-permeable membrane, there will be no net movement of water (which would make osmosis pretty boring).

“Aha”, I hear them say, “but that’s not what we mean by concentration!  We mean the relative number of water molecules compared to the number of solute molecules.  If you define it that way, then you can have higher and lower water concentrations!”  You may think this is an exaggeration or strawman, but it is something I have heard, seen on popular revision websites and on a prominent government funded tree based academy website.

If, in your desire to “keep things simple” you are forced to invent a new definition for an important keyword, a definition that contradicts the one provided in the specification*, then you have gone badly wrong. 

It is a shame that we don’t have terms to describe the situation where there are changes to the relative number of water and solute molecules.  That would simplify everything and get us out of this homonym quagmire.  Oh wait, we do – “dilute solutions” and “concentrated solutions”.

Why didn’t we just use “dilute solutions” and “concentrated solutions” in our definition to begin with?  Almost certainly because we wanted to build on the diffusion lesson and the keyword of “concentration” and didn’t want to overcomplicate or add to the cognitive load of our students by introducing the words “dilute solution” and “concentrated solution”.  I fear it is a common mistake to overcomplicate in our attempts to keep things simple.

Please, if not for me then for the poor potatoes, don’t say “concentration of water”.

Now the diagrams…

Please, if you are drawing diagrams showing water molecules and solvent molecules so you can draw an arrow to show the direction of net flow of water… MAKE SURE THE NUMBER OF WATER MOLECULES IS THE SAME ON BOTH SIDES!

This, the first image that came up on Google images, is an example of what not to do:

First, the reality problem:  In the cup on the left, how is it possible that the water level is the same height if one side has twice as many water molecules as the other?

Second, the pedagogy problem: It is too difficult for students to work out which side of the solution is more concentrated, and which is more dilute.  You are expecting them to count the water and salt molecules (ignoring the “salt molecule” problem), then work out the ratio of each side (holding all of that information in their heads).  Not to mention that the number of water molecules is irrelevant (except of course that it affects the volume of the solution).

An even better approach is to not draw the water molecules at all and just draw the solute.  Something like this:

Now it is immediately obvious which side of the left beaker has the more concentrated solution.  We don’t need to worry about ratios or different coloured particles.  The focus is entirely on the concentration of the solution.  Let’s try and improve the diagrams further.  If I were drawing it, I would use fewer particles.  You’ll inevitably get students counting them to see if they remain the same (time better spent on something else) and you’ll likely get a student who miscounts and then asks where they went/came from – causing the entire class to start arguing about how many particles it started and ended with.

(Also, for both diagrams, I’d use the words “partially-permeable” instead of “semi-permeable”).

In summary, for the love of Poseidon, don’t use the words “water concentration” or “concentration of water” when defining or talking about osmosis.  Don’t draw the water molecules when diagraming osmosis.  And don’t overcomplicate your lessons by inventing new keyword definitions, in an effort to keep things simple.

*The GCSE biology specifications do not include a definition of concentration, but luckily the chemistry specifications do.  For anyone who wants to claim that the chemistry spec definition doesn’t apply to biology, please explain the combined science specification.  Note that none include the idea of relative masses or moles of the solvent compared to the solute.

Natural Selection of Large Mammals, not anymore.

When teaching evolution by natural selection it is very easy just to think about what the examiners need to read in the students’ responses. I know that I constantly hammerhome the sequence:

Within a population there is genetic variation due to random mutations. Some of these mutations may result in different phenotypes. Following environmental change, those with the beneficial characteristic survive and breed. Over many generations the frequency of the beneficial allele increases until all of the population possesses it.

But there is a lot to unpick in that sequence, but the concept always seems to be taught towards the end of the GCSE and A level courses, and the perceived time pressure creeps in preventing me from really digging deeper with my students. However following the Linnean Society Christmas Lecture by Prof Sam Turvey (https://youtu.be/o_lG5RJ5aBs) I am finding myself questioning what we are calling natural selection. 

Again @CMooreAnderson has a lot to answer for,  this time with one of those requests for examples of natural selection. I am sure that I am not alone in thinking of examples of the outcomes rather than the process itself. We think of organisms like the star-nosed mole with a particular set of adaptations, specialists for their environment.

What if what we consider to be specialists were actually on the edge of their existence? Getting squeezed out of their desired habitats to those less than favourable conditions until they are gone forever. 

Prof Turvey gave a fantastic talk that pulled the historic data from spoken and written records in South East Asia to plot range changes since the last ice age to the present day of many large mammals. The range of some species, like the hog badger, is more or less unchanged over the last 11 000 years. However most show a contraction in distribution, but for many it is not a contraction from the edges, but instead the data showed species being pushed to the edges. This is particularly evident with the Sumatran and Javan rhinoceroses. His team showed that the distribution of both overlapped significantly, but are now found in the tiniest discrete pockets in Malaysia and Indonesia. 

It’s not just the rhinos, the patterns of the squeeze are seen in other large mammals like the giant muntjac, Hainan gibbon, giant panda, sika deer, Asian elephant to name a few. So a couple of questions remain, what was the environmental change that they were trying to outrun, and why hasn’t natural selection made them more resilient?

Prof Turvey’s research on the matter points the finger squarely at humans. Our success in growing our population has directly impacted on the megafauna through hunting, food chain disruption, habitat destruction and introduction of non-native species. The rate of change over the last 100 years is simply too fast for what have been relatively stable species for the last 11 000 years. 

From the lecture and the reading, natural selection is not a success story of the specialists but rather a tragedy happening before our eyes. It was this that my Year 11s really engaged with, contemplating the loss of the species that once co-inhabited the planet with us as demonstrated with the ghosts of the megafaunal mammals that once covered the globe. Undoubtedly the loss of species is important for natural selection in the theories we teach, but how can we continue to teach it as a success of the species that are currently still here, when many of these iconic species will be gone within the lifetime of our students.

So perhaps it is time to consider the mundane species, those ubiquitous in our local habitats. Be it bracken, oatgrass or a holly, could you give a convincing story of their evolution through natural selection? Would your students engage with the same enthusiasm when dealing with the weeds outside against the “Attenborough” species from far flung lands? I guess that’s a challenge for me over the next term or so.


Turvey et al (2016) Holocene range collapse of giant muntjacs and pseudo-endemism in the Annamite large mammal fauna. Journal of Biogeography 43: 2250–2260.

Turvey (2018) Mammal extinction risk and conservation in Zachos & Asher Mammalian Evolution, Diversity and Systematics.

Turvey et al (2017) Long-term archives reveal shifting extinction selectivity in China’s

postglacial mammal fauna. Proc. R. Soc. B 284: 20171979.

Our Best Biology Bloggers!

We thought we would collate some of our best biology blogs/bloggers all in one place for your reading pleasure!

If you fancy writing a one off piece that you would like us to host on here to share with the ChatBiology community drop us a DM on twitter or use the contact us form on the site to email us!

We have grouped them loosely around some themes!

Curriculum Sequencing

Pritesh Raichura: Sequencing of evolution – https://bunsenblue.wordpress.com/2020/08/04/curricular-narrative/…

Brett Kingsbury: MRS GREN – https://acommonbiologist.wordpress.com/2020/08/30/is-it-time-to-let-mrs-gren-die/…

Christian Anderson: For all your curriculum deep planning needs! – https://cmooreanderson.wixsite.com/teachingbiology/post/the-scales-of-curriculum-planning-why-sequence-isn-t-king

Adam Robbins: More about sequencing evolution also general great teaching tips! https://reflectionsinscience.wordpress.com/2020/11/15/sequencing-in-gcse-biology-teaching-evolution/

Teaching Methods, “How To Teach Guides”

Dr. Jo Castelino: Great blog for how to’s including this on protein synthesis https://drcastelino.wordpress.com/2020/12/27/how-i-teach-protein-synthesis-at-ks4/

Pritesh Raichura: Faithful diagrams (great example of teaching absorption in the villi) – https://bunsenblue.wordpress.com/2020/04/19/clear-teacher-explanations-2d-faithful-diagrams/…

Pritesh Raichura: Dual coding definitions (includes SA:V) – https://bunsenblue.wordpress.com/2019/12/11/clear-teacher-explanations-2b-dual-coding-definitions-complex-ideas/…

Pritesh Raichura: Dual coding processes (includes menstrual hormones) – https://bunsenblue.wordpress.com/2019/12/04/clear-teacher-explanations-2a-dual-coding-processes/…

Adam Boxer: Modelling magnification calculation – https://achemicalorthodoxy.wordpress.com/2019/12/11/modelling-modelling-into-the-classroom-with-live-drawing/…

Brett Kingsbury: DI in Biology – https://acommonbiologist.wordpress.com/2020/07/15/engelmann-and-faultless-communication/…

Jon Hale: A-Level Biology how to go beyond the CPACS – https://biozone.co.uk/news/83-no-pain-no-gain-looking-beyond-cpac-with-practical-work/

Hinterland/Beyond the Curriculum

Miss J: A great blog about extremophiles from an expert! https://missjsscienceteaching.blogspot.com/2021/01/extremophiles-tiny-organisms-making.html

Dr. Jo: Some great “outiside the box” ideas for enrichment and more! https://drjosciencesolutions.co.uk/workshops-2/dr-jo-blogs/

Jon Hale: Engaging young people through a Royal Society Partnership Grant –https://besteachingandlearning.wordpress.com/2020/01/21/engaging-young-people-through-a-royal-society-partnership-grant/

Jon Hale: British Ecological Summer School Experience –https://www.britishecologicalsociety.org/bes-18-18-summer-school-2018-teachers-perspective/

The Sequencing of A Level Enzyme Practical Lessons

I teach OCR A Biology in a small, non-selective, 11-18 girls school in Jersey. This year the school has moved to a 6 hour per week per subject timetable to aid this difficult transition based upon the end of the students’ Year 11 experience. Early on in the term, it was clear that the lack of forced revision for terminal examinations meant that learning from the early topics of GSCEs, eg Cell Structure, Digestion, etc, was not solid. This term has been a juggle reviewing and consolidating their learning from the last 3 years, whilst raising it to A level standard. The need for concrete observations for abstract concepts has never been greater at my school.

That being said, what I am going to outline is our usual plan for enzyme practicals for Y12. Some cohorts get a little bit more, some get a little bit less in terms of practical opportunities depending on the department finances, lost time due to special assemblies, and timetabling (we have some students taking A levels at other collaborative schools which may mean that they’d be predictably 10 minutes late each week).

In terms of the specification, 2.1.4 d (ii) practical investigations into the effects of pH, temperature, enzyme concentration and substrate concentration on enzyme activity is it, but to meet the requirements for the Practical Endorsement students would only need to do a single enzyme practical. So why bother doing anymore?

For me the benefits or practical work are clear. Each observation offers a tangible link to the concept for higher level thinking, building schema. By no means I am suggesting that practical work replaces the explicit instruction, but rather forms an essential part of the scheme. As students become confident applying their knowledge to the observed trends, the application of mathematical skills becomes embedded rather than a bolt-on, and their grasp of those practical skills becomes a fluency.

At GCSE, most students will only have done a starch and amylase spotting tile practical. Although it is a perceived “rite of passage” I am not a fan. How ridiculous is it that the only enzyme practical they end up doing relies on the interpretation of negative results. Cognitive Load?! Then there’s the quality of the data relying on the frequency of samples, which then requires students to be “on it” from the off. So the Y12 plan takes a backward step:

Practical 1 – How does the source of catalase affect the rate of hydrogen peroxide decomposition?

Most students have seen the elephant’s toothpaste demo in Chemistry, with manganese (IV) oxide but I do it again as the foundation of catalysts, exothermic reactions and measuring change. In terms of what I want them to develop, it’s the competence in collecting oxygen by the displacement of water and what standard deviation actually shows. Using bacterial catalase, baker’s yeast, celery, potato and bovine liver as the sources gives the opportunity to think about the conservation of the gene across kingdoms and why it’s there (Spec point 2.1.4 b), why different versions of the enzyme may exist (I’ve had a couple of students in the past delve into the phylogenetic analysis of the gene), but also what else may be happening with the idea of eliciting confounding variables such as surface area, concentration, etc.

Practical 2 – How does the concentration of catalase affect the rate of hydrogen peroxide decomposition?

At this point students have had a little experience of serial dilutions, but are not typically competent in this yet. So this practical is about developing the skill, and using ICT to support data analysis. By pulling the class data together it gives the opportunity to see the spread of data achieved despite using the same method, and same source of catalase. Which leads them to recalling the other factors which they have come across at GCSE.

Practical 3 – How does temperature affect the rate of hydrogen peroxide decomposition?

So now is the first introduction of thermostatically controlled waterbaths, and one of those life skills where what it says on the front, may not be what’s inside. This is the first point that resolution of analogue instruments is dropped in, when using a thermometer as the example. The catalase is at an agreed concentration from the previous practical based upon manageable data collection, typically they choose 1% catalase solution. At this point they are pretty confident compiling their class data, calculating the standard deviation and plotting the results. Typically the students calculate a Q10 between 1.5 and 1.85 which I think is good enough, at least they get to calculate it from their lines rather than textbook data. In terms of the theory, I like modelling the impact of temperature using hair curling foam things to show what denaturing an enzyme means in terms of shape change. Within the practical itself, the enzyme and substrate are preheated which brings in the application of activation energy as the hotter waterbath will show that hydrogen peroxide will decompose without the enzyme present giving the rationale for control experiments.

Practical 4 – How does pH affect the rate of hydrogen peroxide decomposition?

The waterbaths are at their optimum temperature from the last practical, but the catalase solutions has been made with different pH buffers. Depending on the time and resources available students record the pH of these solutions with pH probes, or just note what is down on the outside of the beaker. At this point no students typically require any assistance beyond the title on the board.

Practical 5 – How does the concentration of hydrogen peroxide affect the rate of oxygen production by catalase?

Serial dilutions again, this time using pH buffer instead of distilled water. Usually they are competent by this point and need no assistance. They get good data, the standard deviation is pretty sound too. I should mention that we don’t need to reference Michaelis-Menton at all, but vMAX is the limit of what they need. The students are pretty good at this point when it comes to explaining their data because it is only one thing to consider each time so they communicate effectively using the appropriate terminology.

Practical 6 – How does the concentration of copper sulfate solution affect the rate of oxygen production by catalase?

They do the dilutions for both the copper sulfate – catalase solution and the hydrogen peroxide. The data that comes out is good, they see what non-competitive, irreversible inhibition looks like on the graph. I would like to slot one more in with competitive inhibition but I think that limits us to cyanide ions which would take a battle to allow.

Practical 7 – How do chloride ions affect the rate of amylose digestion by amylase?

So it’s not catalase, but it is a specified enzyme, with the specified co-factor, so how to make it not a spotting tile mess? Answer: realtime colourimetry using the data harvest protocol. The nice thing about this is that the students can analyse the initial rates of reactions and make quantitative judgements regarding the effect of co-factors.

So that’s it. Undoubtedly there is a myriad of enzyme practicals that could slot in here, but I prefer to put the others in the topic context rather than the enzyme concept. Enzymes are central to so many of our phenomena, it is only right that students are experts before they get to named processes like photosynthesis.

If you would like any help with the technical support for any of the practicals, data sets or Google Form templates for class data, just let me know.

J. Hale

Twitter: @BeaulieuBio

The philosophy of biology: How it affects curricular design

During my teacher training we had to write a masters’ level essay on the implementation of the How Science Works component of the English secondary science curriculum. There was a bit of confusion as to what this really was, and many schools seemed to view it as a bolt-on exercise to appear intermittently (if at all) to tick boxes. It was seen principally as the ‘scientific method’, which meant to most people ‘how to design and carry out an experiment’.

But there’s so much more to it than this. Rather than making intermittent appearances, it transcends the curriculum, read more here:

Christian Moore Anderson


How I Teach The Heart: Part 1

This is the first in a series of posts where I will go through how I teach different topics in biology. This post will focus on how I teach the structure of the heart so pupils can identify the four chambers of the heart, the vessels of the heart, which parts of the heart contain oxygenated or deoxygenated blood, and finally the pupils should be able to describe the route blood takes through the heart.

The aim of these posts is to explicitly guide you through my lesson, including all the diagrams I draw under my visualiser, the questions I ask the pupils, what I think ‘differentiation’ is at any given point, the tasks I give pupils, and any other aspect I think is important to teaching the structure of the heart.

This blog will be split into the following sections:

  1. Introducing what the pupils will be learning
  2. ‘Dialogic’ Direct Instruction of the initial teaching of the heart

1a: How I introduce what I am teaching the pupils

The pupils have just completed self-assessing the retrieval Do Now quiz on the components of the blood, so I skip to the next slide (or image of the heart from the textbook placed under the visualiser). The slide has one image, which is a fully labelled diagram of the heart.

I pause, and then point at the image and say:

“Year 10… Today you will learn the structure of the heart, and by the end of the lesson you will be able to describe the route blood flows through the heart.”

That’s it. There are no meaningless out of context Learning Outcomes for pupils to read through, copy down, or stick in their books – just an image of the heart – an image that contextualises what success will look like at the end of the lesson.

1b: ‘Dialogic’ Direct Instruction

When you ask people to envisage what good Direct Instruction looks like, many people will see a teacher explaining something with absolute clarity, while the pupils sit in silence, as they nod along.

But I have added the word dialogic, because I see Direct Instruction as a shared dialogue between teacher and pupil, where I explain something, and after every new explanation I ask the pupils questions to check for understanding and explore it’s meaning. This is as opposed to monologic Direct Instruction which refers to the teacher simply transferring the knowledge to the pupils without clarification of meaning through questioning (or discussion).

I see teaching as a conversation of ideas. I tell the pupils something and they show me they understand it by speaking to me about it by answering my questions and then answering the questions I set them during their independent practice.

In my opinion direct instruction is singularly the most important part of the lesson, and hence the most important aspect of your practice as a teacher. This is because Dialogic Direct Instruction is what separates you from a lecturer or YouTube video, which is your ability to check for understanding and change the course of the lesson while/after you explain something.

I always tell PGCE or NQTs (or any teacher) that they can give the students the most well thought through activity or ask them with expert skill every question under the sun to check for understanding. But if you haven’t explained the science with absolute clarity, then the pupils can’t access your perfectly designed activity, answer your perfectly crafted questions, or answer the perfect retrieval Do Now questions in the next lesson. If you have’t explained it well, then they won’t learn.

I am robotic in my teaching, and the first thing I do with a new topic is think about how I can break down the whole picture into smaller chunks that build on one another through the lesson.

I firstly decide what the chunks are in the topic I am teaching, and when teaching the heart these chunks will be:

  1. name of four chambers
  2. artery vs vein
  3. naming the vessels
  4. describing the route blood takes through the heart
  5. oxygenated and deoxygenated blood
  6. describing the route blood takes through the heart including step v.

After I have decided on the chunks of the topic, the next thing I think about is how I will explain it under the visualizer using a technique called dual coding, which is drawing the thing you’re teaching and explaining it as you are drawing it. For this topic, I will spend a few minutes practicing drawing the outline of The Heart and blood vessels.

I have now planned what I will be teaching and in what order, now I think about the questions I will ask the pupils during each chunk, and after each chunk. These questions are checking to see if they are following and understand, so when they get to the independent practice part of the lesson, they can answer the questions.

I use the following techniques for the different parts of each chunk.

  1. During a chunk: I use Cold Calling to target random pupils
  2. After a chunk: I use mini whiteboards to assess the whole class

I now know the chunks I will teach the pupils, I have planned the drawings I will draw to explain each chunk, and I have planned the questions I will ask the pupils during each chunk.

This brings me on to what I do during Direct Instruction for each chunk. I am now going to explain how I use dual coding to teach my pupils the structure of The Heart.

Chunk 1a: The four chambers of the heart (atrium and ventricles)

I draw the image of the heart below under my visualiser, and as I draw I am describing what I am drawing.

“This is the structure of the heart. I am drawing the four chambers of the heart. The two top chambers are called atrium, the two bottom chambers are the ventricles”

It’s at this point that I check for understanding. I use Cold Calling, whereby I chose a student at ‘random’ to ask question(s), although I almost always chose the pupil in the class who typically doesn’t listen or can be silly, or the underachieving pupil, I rarely chose the brightest pupil.

With the diagram on the board I ask them:

‘Are the atria the top or bottom chambers?’

‘What’s the name given to the bottom chambers?’

I will then Cold Call another pupil with these questions or similar ones, again choosing a ‘silly’ or ‘underachieving’ pupil.

We are now at the end of the chunk – Pupils prepare their mini whiteboards.

I replace my labelled heart diagram with an unlabelled diagram under the visualiser.

I ask the following questions:

[pointing at unlabelled atrium]          “What are the top two chambers called?”

[pointing at unlabelled ventricle]       “What are the bottom two chambers called?”

Chunk 1b: The four chambers of the heart (left and right sides)

I now add to this knowledge by telling them that the heart has a mirrored right side and a left side. The image below shows how I label the right and left side of the heart under the visualiser as I explain this. I will also pick the image up and hold it against my chest to show them that the right side on a heart image represents it’s orientation within a person.

I replace my labelled heart diagram with an unlabelled diagram of the heart under the visualiser.

I now Cold Call a couple of students with these questions:

[pointing at unlabelled left atrium]                “What side of the heart is this?”

[pointing at unlabelled right ventricle]          “What side of the heart is this?

We are now at the end of the chunk – Pupils pick up mini whiteboards.

The questions below show an increase the difficulty of the questions as I ask them:

[pointing at unlabelled right atrium]              “Is this the left or right atrium?

[pointing at unlabelled right ventricle]           “Which chamber is this?

[pointing at unlabelled left ventricle]             “Why is this not the right atrium?

*Important point* Just because the pupils are parroting back what you have just told them – doesn’t mean they have learned it. The questioning at this point is part of my dialogic direct instruction – making sure they are following and understanding as I teach them.

Chunk 2: Arteries vs veins

I use my professional judgement and now *think* the pupils have an understanding of the four chambers of the heart, so I move onto the next chunk, which is also the hardest part of the lesson – getting the pupils to remember all the vessels that connect the heart.

It’s very easy to jump straight into naming each vessel and bypassing the foundation of all blood vessels – which is the ability to identify an artery or vein.

  1. I draw arrows leaving the heart from the pulmonary artery and state this is an artery because blood is leaving the heart via this vessel
  2. I state Artery beings with the letter A and transports blood Away from the heart
  3. Draw an arrow towards the heart highlighting the pulmonary vein

I point at the pulmonary artery and Cold Call a pupil, and ask them:

If I tell you this is an artery [pause]… will the arrow point to the heart or away from the heart?

What I like about this type of questioning is that I am telling them a piece of information, that this is an artery, I then pause, and then ask them a question to make them think about this new piece of information.

With 30 other pupils in the room – all of them are currently answering this question in their heads eagerly awaiting the pupil I asked to get it wrong, giving them the opportunity to answer the question instead. I will talk more about this type of questioning later in the post.

I repeat this question for the vena cavas with another pupil, and we end up with the diagram below as I re-clarify that arteries transport blood away from the heart and veins transport blood to the heart.

We are now at the end of chunk 2, and it is time to assess the pupils on what they have understood during chunk 2.

Before I get the pupils on their mini whiteboards, I will Cold Call question the pupils to check for understanding (not learning).

Questions I ask several pupils:

[pointing at aorta with arrow pointing away] – “Is this a vein or an artery?”

[pointing at pulmonary vein with arrow to heart] – “Is this a vein or an artery?”

[pointing at pulmonary vein with arrow pointing to heart] – “Why is this a vein?”

[pointing at pulmonary vein with arrow pointing to heart] – “Why is this not an artery?”

I am now at the point of lesson where I want to check for understanding of the whole class.

So even though this is the Direct Instruction part of the lesson – I want feedback and need to know if they pupils have followed. If by this point, they don’t know the four chambers of the heart, or the difference between a vein and an artery, I will have to go back and start my direct instruction from the beginning – No. Matter. What.

At this point I am going to assess them on *everything* they have learned so far.

I place a piece of paper over each label of the heart chambers like in the diagram below, and I start with easy questions to guide their thinking on this new and difficult topic.

I ask the pupils to get their mini whiteboards and ask the following questions:

  1. [Pointing at aorta]                              “Is this an artery or vein?”
  2. [Pointing at pulmonary vein]           “Is this an artery or vein?”
  3. [Pointing at pulmonary artery]        “What type of blood vessel is this?”
  4. [Pointing at right ventricle]      “Is this a ventricle or atrium?”
  5. [Pointing at left atrium]                      “Is this the right or left side of the heart?”
  6. [Pointing at right atrium]                   “What is the name of this chamber?”
  7. [Pointing at the left ventricle]           “What is the name of this chamber?”

If you see a mistake at any point during this whole-class mini whiteboard questioning, you must stop and correct the pupil and explain why they are wrong and ask them a similar question to re-test to see if they get it correct.

*You must not ignore the wrong answers written by pupils*

I am now sure the pupils understand the difference between arteries and veins, and can identify the four chambers of the heart, so I feel confident to move onto teaching the names of the blood vessels.

Chunk 3: Naming the blood vessels of the heart

I now draw the heart diagram again, and as I do this, I re-describe the structure incredibly briefly.

The first vessel I draw is the pulmonary artery, and as I draw the artery, I tell the class that pulmonary means lungs.

I then go on to state:

“it is called an artery because it transports blood away from the heart, and it’s called the pulmonary artery, because it carries blood away from the heart to the lungs.”

I then draw the pulmonary vein leaving the lungs and connecting to the left atrium.

At this point I ask the pupils to predict the name of the pulmonary vein and state their reasoning on their mini whiteboards.

The answer I hope to see is: “pulmonary vein – takes blood from lungs to the heart”

After the pupil’s prediction I explicitly explain that:

“the pulmonary vein is a vein because it transports blood to the heart, and it’s called the pulmonary vein because it transports blood from the lungs to the heart.”

I now Cold Call pupils with the following questions:

  • [Pointing at pulmonary artery] “Is this a vein or artery?”
  • “Why is it an artery?”
  • [New pupil]: “Why is it not the pulmonary vein?”
  • “Compare the pulmonary artery and vein”
  • [New Pupil] “Which chamber does the pulmonary artery transport blood form?”
  • “Which chamber does the pulmonary vein transport blood to?”

At this point I teach the name of the aorta and the vena cavas.

The aorta and vena cava have no obvious link to their function from their names. A way to teach a pupil this information is by stating a piece of information – pausing – and then ending with a question.

I say: The Aorta transports blood away from the heart to the body [pause] is it a vein or artery?”

What I am doing here is giving them information in red. I then pause to let the pupil process the information, and then ask them the question in green. This gives all the pupils in the class time to think before I Cold Call a pupil. I then label the heart with the word ‘aorta’, and repeat back to the class that “the aorta is an artery that transports blood around the body”

I say:The Vena Cava transports blood to the heart from the body [pause] is it a vein or artery?”

What I am doing here is giving them information in red. I then pause to let the pupil process the information, and then Cold Call a pupil asking them the question in green.

Because this is the first time they have seen this information – I am not testing the pupils for whether they have learned the information, but instead to check their understanding. So I use questions like the ones below when I Cold Call multiple pupils with an unlabelled image or use mini whiteboards to assess the whole class.

  1. [Pointing at Pulmonary Artery] This vessel transports blood to the lungs, what is it called?
  2. [Pointing at Pulmonary vein] This vessel transports blood from the lungs to the heart, what is it called?
  3. [Pointing at Aorta] This vessel transports blood to the body, what is it called?
  4. [Pointing at vena cava] This vessel transports blood from body to the heart, what is it called?
  5. Which vessel transports blood to the right atrium?
  6. Which vessel transports blood to the left atrium?
  7. Which vessel transports blood away from the left ventricle?
  8. Which vessel transports blood away from the right ventricle?

I am constantly checking for understanding, and making the pupils work with the new knowledge in low stakes assessment.

Chunk 4: Oxygenated and deoxygenated blood

I now move onto which chambers and vessels contain oxygenated or deoxygenated blood.

I start with deoxygenated blood entering the lungs and represent deoxygenated blood with blue pen (stating that blood is red – and this is just a model). I draw blood being represented by blue pen entering the lungs, and reiterate blood isn’t blue – this is a common misconception.

I start here because pupils will always be able to say something basic like ‘Blood gets oxygen in the lungs and gives away carbon dioxide out of the lungs’.

I draw the lung connected to the heart via the pulmonary vein and artery.

I now use a red pen to show blood being oxygenated in the lungs, and that oxygenated blood is transported through the pulmonary vein to the right atrium.

I now ask a pupil to go through the route the blood takes through heart.

At this point I state that the oxygenated blood leaves the heart to the body via the aorta to deliver oxygen to respiring cells (really important to remember that many pupils won’t know what respiration is – so you can keep it simple and say that oxygen is delivered to cells to keep them alive). I then say that deoxygenated blood returns to the heart via the vena cavas and use blue pen to show this.

I then describe explicitly the route deoxygenated blood takes through the heart and back to the lungs via the pulmonary artery, always using red and blue pen to differentiate between where oxygenate and deoxygenated blood is found in the heart.

Once I have explained which vessels and chambers contain oxygenated or deoxygenated blood, I interleave chunks 1, 2, and 3 with chunk 4.

I now move on to question them and use the technique shown above for questioning where I make a statement, pause, ask a question and then Cold Call pupils or use mini whiteboards.

Examples of these questions can be:

I say: deoxygenated blood returns to the right side of the heart through which vessel does the deoxygenated blood return to the heart?

I say: oxygenated blood returns to the left side of the heart – through which vessel does the oxygenated blood return to the heart?

I say: oxygenated blood leaves the left side of the heartthrough which vessel does oxygenated blood leave the heart?

How to know if you can move on?

I have questioned the pupils throughout the Direct Instruction of The Heart. I feel like we can move onto the next stage of the lesson, which is modelling the heart, whereby we draw and label the heart as a class and write a modelled piece of writing using a gap fill task. This will be the next blog post, which will describe different scaffolded tasks you can use.

People who have inspired me to teach the way I do are listed below. Thank you!

Doug Lemov: Teach Like a Champion

Adam Boxer: Blogs

Ruth Ashbee: Blogs

Kate Jones: Retrieval Practice

Mary Myatt: The Curriculum: Gallimaufry to Coherence

Mark Enser: Teach Like Nobody is Watching Book

Pritesh Raichura: blog here

Oliver Caviglioli: Dual Coding

David Rodger-Goodwin: Blog

Andy Tharby: Book on Explaining stuff

Tom Sherrington’s blog

Daisy Christodoulou: Formative Assessment book

Dylan William


Beyond description: Begin your biology curriculum with autopoiesis

Brett Kingsbury has declared MRS GREN dead. Beginning secondary biology education is a pivotal time for instilling the correct epistemic view of our subject, so what do we replace it with? Here’s my take:


Christian Moore Anderson

@CMooreAnderson (on twitter)