A model for sequencing in Biology

Over the past year, I have slowly developed a model of how I atomise and sequence a Biology topic. I’ve put together a series of blog posts that outline this model and also what it ends up looking like in the classroom. The biggest influences on this model are Pritesh Raichura’s blog on designing a Science curriculum and Kris Boulton’s “My best planning” series, particularly parts 1 and 2. These posts provided me with concrete examples of concepts like categorising knowledge, atomising content to make the implicit explicit and sequencing. They’re based on the foundations of Sweller’s Cognitive Load Theory, Engelmann & Carnine’s Theory of Instruction and Rosenshine’s Principles of Instruction.

I’m a big advocate of ensuring we emphasise the “why” alongside the “how” so as to minimise the opportunity for lethal mutations. However, I don’t want these blogs to lose focus by explaining each and every principle behind my choices. To this end, I have linked to blogs, articles etc. where I refer to a “why” behind my “how”. Please check out some of the these links if they’re unfamiliar.

Part 1 of this series will focus on how I gradually atomise a topic from principles to big questions to sentences to facts and how each level contributes towards the sequencing of the topic into a coherent narrative. Parts 2, 3 and 4 will then explore how my instructional design builds the atoms back up, ensuring there’s practice to fluency at each level. Finally, part 5 will look at how I layer the levels in a learning episode so that you get a feel of what a lesson or a sequence of lessons using this model looks like.

Part 1 – Organising the atoms

The example I give in this blog series is based on a topic from the GCSE specification. I’m not saying this is should be the limit of content choice but others have written more eloquently on the weaving of hinterland in to augment the core. Plus, this just isn’t a current priority with my GCSE classes who have spent their KS3 years doing card sorts and information hunts.

Building a narrative through principles

I start with the specification for the topic. Here’s the Edexcel GCSE specification for Topic 7 Animal coordination, control & homeostasis. There’s a lot of higher and triple only content in this topic, so the resulting sequence might look very different depending on the class in front of you. I’m going to assume a triple class of predominantly higher tier students.

I’m looking here for overarching principles that might produce a narrative for several specification points. A nice method for doing this might be something similar to Fabio Di Salvo’s “smashing the spec” approach. Here’s what I initially come up with:

  1. Hormones coordinate responses to internal and external stimuli. (7.1, 7.2, 7.3, 7.4, 7.5, 7.13, 7.14, 7.20B)
  2. Hormones control the fertility of human females. (7.4, 7.5, 7.6, 7.7, 7.8)
  3. Homeostasis maintains a constant internal environment through negative feedback. (7.3, 7.9, 7.10B, 7.11B, 7.12B, 7.13, 7.14, 7.15, 7.16, 7.20B)
  4. The regulation of water content in the body is at odds with the need to excrete soluble waste. (7.18B, 7.19B, 7.20B, 7.21B, 7.22B)

There is always likely to be overlap and this helps to sequence the principles into a coherent story. For instance, I can see that principle 2 could be used as an introduction to hormones and negative feedback or as consolidation of those ideas following other examples. Principle 1 is very broad but could focus on the comparison of internal and external stimuli using the hormones adrenaline and thyroxine that both affect metabolic rate. Principle 4 needs to sit inside principle 3 as a precursor to ADH regulating water content as prior knowledge of the kidney is required to understand this. A result of all of this might look like this:

  1. Hormones coordinate responses to internal and external stimuli.
    1. Adrenaline and thyroxine comparison
  2. Homeostasis maintains a constant internal environment through negative feedback.
    1. Insulin & glucagon and negative feedback
    2. Thermoregulation as nervous example
    3. The regulation of water content in the body is at odds with the need to excrete soluble waste.
    4. ADH and negative feedback
  3. Hormones control the fertility of human females.
    1. Consolidation of negative feedback

The big questions

Within each of the principles are many possible big questions. These are the most challenging questions I want my students to be able to answer. I’d be lying if I said I wasn’t thinking about possible exam questions here. In fact, I use the various exam board question banks (Exam Wizard, Exam Builder etc.) as inspiration. But it’s not my only motive. If there was something outside of the specification that I thought was essential, I would include it without hesitation.

Let’s focus on what is now the last principle, “Hormones control the fertility of human females.”. Some of the big questions within this principle might be:

  • Explain how the 4 menstrual hormones interact to prevent further ovulation during pregnancy through negative feedback.
  • Explain how hormonal contraceptives prevent pregnancy.
  • Explain how hormonal therapy can be used to increase the chances of pregnancy.

I can now start to sequence the content within the principle. The questions above are largely in order. I need to teach the menstrual cycle and hormones first before looking at their application in contraception and fertility treatments. Let’s add this detail to my sequence:

  1. Hormones coordinate responses to internal and external stimuli.
    1. Adrenaline and thyroxine comparison
  2. Homeostasis maintains a constant internal environment through negative feedback.
    1. Insulin & glucagon and negative feedback
    2. Thermoregulation as nervous example
    3. The regulation of water content in the body is at odds with the need to excrete soluble waste.
    4. ADH and negative feedback
  3. Hormones control the fertility of human females.
    1. Menstrual cycle and hormones
    2. Contraception
    3. Fertility treatments

Sentence structures

Each of these big questions requires students to construct and organise sentences. I would produce a model answer to “Explain how the 4 menstrual hormones interact to prevent further ovulation during pregnancy through negative feedback.” and then pick apart the sentences, looking for common grammatical structures that would be beneficial to practise. This also gives me an opportunity to collate the tier 2 vocabulary that students will require. Words like stimulate, inhibit, secrete, mature etc. are likely to require the same explicit teaching and spaced retrieval that the biological content itself requires. Some of the sentence structures are below along with concrete examples:

  • Chronological sequence of the events of the menstrual cycle e.g. Menstruation occurs before ovulation.
  • Chaining the gland, target organ and effect for each hormone e.g. FSH is secreted by the pituitary gland, stimulating a follicle to develop in the ovary.
  • Comparing the gland / target organ / effect of 2 or more of the hormones e.g. Both oestrogen and progesterone are secreted by structures in the ovary and effect the uterus lining.
  • Connecting the inhibition / stimulation relationships between the hormones e.g. Oestrogen stimulates the secretion of FSH.
  • Consequences of various scenarios e.g. If the egg is fertilised then the corpus luteum remains in the ovary secreting progesterone.

With my sequencing hat back on, I can see that I should start with the events and language of the menstrual cycle before introducing the roles of the hormones and finally how they interact to produce negative feedback. So now my sequence looks like this:

  1. Hormones coordinate responses to internal and external stimuli.
    1. Adrenaline and thyroxine comparison
  2. Homeostasis maintains a constant internal environment through negative feedback.
    1. Insulin & glucagon and negative feedback
    2. Thermoregulation as nervous example
    3. The regulation of water content in the body is at odds with the need to excrete soluble waste.
    4. ADH and negative feedback
  3. Hormones control the fertility of human females.
    1. Menstrual cycle and hormones
      1. Events of menstrual cycle
      2. Roles of menstrual hormones
      3. Negative feedback
    2. Contraception
    3. Fertility treatments

Factual atoms

Lastly, I identify the factual knowledge required to construct these sentences (and, ultimately, the answers to the big questions). Using just facts about oestrogen as an example:

  1. The follicle in the ovary secretes oestrogen.
  2. The target organs of oestrogen are the uterus and pituitary gland.
  3. The effect of oestrogen on the uterus is to stimulate the repair of the uterus lining.

This is what I would describe as microsequencing. I’ll start to spot where one fact has to come before another in order to make sense. From the above example, the order of fact 1 and fact 2 is not hugely important as they can be chained in a sentence in either order. But fact 2 must come before fact 3 as fact 3 is a consequence of fact 2.

  1. Hormones coordinate responses to internal and external stimuli.
    1. Adrenaline and thyroxine comparison
  2. Homeostasis maintains a constant internal environment through negative feedback.
    1. Insulin & glucagon and negative feedback
    2. Thermoregulation as nervous example
    3. The regulation of water content in the body is at odds with the need to excrete soluble waste.
    4. ADH and negative feedback
  3. Hormones control the fertility of human females.
    1. Menstrual cycle and hormones
      1. Events of menstrual cycle
      2. Roles of menstrual hormones
        1. Glands, target organs and functions of oestrogen & progesterone
        2. Glands, target organs and functions of FSH & LH
      3. Negative feedback
    2. Contraception
    3. Fertility treatments

Now I’m not going to pretend that this is not a time consuming process. But what I’m left with at the end is a huge chunk of my planning for a topic completed and a deep understanding of the structure of a topic. I have model answers to big questions that I can live write, sentence structures as the basis for deliberate practice and factual atoms to populate quickfire comprehension questioning. I think it’s a worthwhile investment.

In part 2, I’ll look at how I introduce new content at the factual level, ensuring lots of practice in these building blocks ready for sentence construction.

If you have any questions regarding this model, please leave a comment or get in touch through Twitter.

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