Sequencing in GCSE Biology: Teaching Evolution

I started to read The Ape that Understood the Universe by Steve Stewart-Williams and it got me thinking about the teaching of evolution. I posted a quick survey on twitter because it occurred to me that the sequencing of ecology and evolution is quite varied. In this blog I want to discuss the various ways it can be sequenced, why I am in favour of a particular way and then go on to talk about how I am going to teach it. 

Biology teachers using AQA: Do you teach 'Ecology' before 'Inheritance, Variation and Evolution'? @chatbiology @cogscisci #asechat

— MrARobbins (@MrARobbins) November 7, 2020

Sequencing   

The majority of schools teach AQA combined trilogy, so for the sake of brevity, and so I can draw on my own experience, I will be using the AQA trilogy spec as a starting point. I am also aware that some schools ignore the prescribed units in the spec and mix paper 1 and 2 content. For assessment pragmatism I am also going to keep all paper 1 in yr10 and paper 2 in yr11 as I think this will make my argument more concise and generalisable to most schools.

The trilogy specification orders biology content with Inheritance, Variation And Evolution (IVE) before Ecology. While a specification should not be considered a suggested route through, there is some logic to this. Understanding adaptation and competition might be easier with a good understanding of evolution, DNA and mutation. The other main option is to put Ecology at the end of year 10/ beginning of year 11. This is often chosen for pragmatic reasons, the field work is better in the summer and ecology has an important required practical that is often assessed.

I am going to argue the case that it is important to teach Ecology first from a teaching perspective.

Cognitive science and common sense tell us that it is easier for students to go from concrete to abstract concepts. However, In biology teaching we often seem to forget this. I put this down to the curse of knowledge. Once we have a developed schema we think of biological concepts from ‘small to big’. In this case from genes to adaptations. However, for a novice it is much more beneficial to draw on the concrete ideas of adaptation and work from ‘big to small’. Looking at that survey a lot of teachers are getting it wrong: Ecology needs to be taught before IVE.

This is the reason why ecology should be taught first; it provides a strong foundational understanding of competition and adaptation which can be used to construct the theory of evolution.  

Students have often discussed adaptation and competition in KS3 and even KS2. They also have a tacit understanding of these concepts from their everyday experiences. There is less of a barrier to understanding that organisms compete and over time adapt to their surroundings. However if inheritance is taught first then the students are required to internalise a large volume of novel words and concepts. If this is our foundation for explaining evolution then it is more likely to be unstable and prone to misconceptions. Within the IVE unit you can even sequence it to build up their understanding of genes and alleles before teaching evolution if you want. That way they students have all the prerequisite knowledge required.

A quick word on ability

Before I get into how I plan on sequencing evolution this year; a quick word on ability. If you are teaching high ability students you have a lot more flexibility in how you teach them. You can mix up the order and use ineffective techniques, they will still learn. They will learn slightly less than they should but they are thoroughbreds so it will be barely noticeable. This blog is not about teaching those students. It is about teaching the low to middle ability students. Those that are in the area of a grade 3 or 4. They are the ones who we need to optimise our teaching for because with ineffective techniques and sequences they get lost and give up. They can understand evolution if we teach it the right way.

Introducing evolution

For my explanation of evolution I want to achieve two things initially. I want to go from concrete to abstract and I want to try to use a series of examples that expand on each other so only one concept is being introduced at a time. 

The basic outline could be:

1. Competition: check prior knowledge and address any misconceptions
2. Adaptation: To hunt 
3. Adaptation: Cold climate
4. Adaptation: Hot climate 
5. Adaptation: Remember kids; plants exist
6. Adaptation: Reproductive
7. Defining survival
8. Gene machines
9. What is a species
10. Evolution
11. Evidence for evolution
12. Structuring answers
13. Worked example
14. Student practice

1. Competition

This will be pure retrieval for the students. Quick paired discussion and then complete a venn diagram to show similarity and difference between plants and animal competition.

2. Adaptation: To hunt

I wanted to start with an example that exemplifies the most obvious adaptations and the simplest idea of survival; food. I want it to be a familiar, but also interesting animal. I’ve gone with a bald eagle. I’m hoping most students will be able to identify the obvious features to aid hunting and some less obvious like eyesight.

3. Adaptation: Cold climate

Next we move to a very familiar example: the polar bear. We are shifting to the idea of survival as adaptation against hostile climate conditions 

4. Adaptation: Hot climate

Other side of the climate response. I’ve gone with the fennec fox to ensure the students can give me a good answer that revolves around surface area and heat loss.

5. Adaptation: Remember kids; plants exist.

I’m very conscious that this is very animal-centric. I’ve done this on purpose because animals are much more relatable for students and also because I’m not a fan of plant biology in general. So a simple cactus example should remind students of all the relevant adaptations.

6. Adaptation: Reproductive

This is where I’ve taken a detour from what I would have normally done. I want to introduce the peacock and let students try to justify its adaptations. I expect they will suggest the feathers are to scare off predators possibly. Then I want to contrast it to the peahen. I will use this contrast to try and get across the idea that survival is only useful if you reproduce and all the other adaptations that we see that seem silly from a survival point of view and there to increase the chance of attracting mates. I feel this is an area that is often ignored but is useful as a way to enhance the ‘pass on genes’ aspect of the theory of evolution.

7. Defining survival.

I want to clearly unpick what students mean by survival. This will essentially follow the rationale laid out in the examples. We will go from ‘not dying’ to ‘passing on genes to offspring’ This answer still does not explain group selection pressures, like ant communities, but that is not within the reach of the GCSE specification so it is probably best left alone.

8. Gene machines.

Now the students realise the importance of passing on genes we can describe organisms as gene machines and define this. I like it because it has a nice ring to it and I think the students will find it memorable. 

9. What is a species?

Throughout the discussions and work students will have used the word species and know its rough applicability conditions. But will they really know what it is? Again I want to use clear examples of known species to illustrate the key point of fertile offspring. I’ve chosen a horse and donkey creating a mule. 

10. Evolution

Now we come to clearly stating the theory of evolution. I have decided not to tell it as a story. While I appreciate the value of stories, i think for evolution I am going to try and make it as clear as possible without any seductive details. Those can come in with the practice questions. I’ll save finches and peppered moths for the students’ practice.

11. Evidence of evolution

Here I want to draw in the evidence from fossils and antibiotic resistance to show a variety of time scales and ensure students understand they do not need to consider the theory’s validity in this topic.

12. Structuring answers

The most important thing is for the students to fully understand the idea of evolution. The second most important thing is for students to understand the mark scheme. This is often the case in biology. Evolution needs scaffolding to encourage students not to leave the page blank due to intimidation. There are a few different versions available. I heard about this one from a tweet and then added separation to it. It seems to me that the idea of speciation is prevalent in current exam spec and so I place it in brackets because sometimes it will be relevant and other times not.

13. Worked example

Simple. Using our booklets we will work through an evolution problem with me showing how I structure my answer.

14. Student practice

Using guidance fading we will work through a few examples before letting the students lose on some exam questions.

A slide deck of the images that will take you up to step 12. I’ve tried to create is minimal to allow students to focus on my voice. I would write additional notes and diagrams on my whiteboard as appropriate. Download it here.

I think this sequence will help students grasp a deeper understanding of evolution. I think it will support the less able students to get the key concepts and be able to apply them in a question. 

I may be wrong. I’d be interested to know your thoughts. After all, discourse is how we grow as teachers.