A peek inside my lessons: How I teach osmoregulation

I started my career in 2003 as a Biology teacher. While nowadays I spend more of my time teaching chemistry, I still love to get stuck into some biology. One of the unusual benefits of covid related staff absences last term was the chance to get back to teaching some biology when I covered the triple science class.

Activating prior knowledge

This lesson starts with a section on activating and checking prior knowledge. We all know that students only learn by building on their existing experiences and knowledge. After all, going from the known to the unknown is a staple of teacher training. Here I want to give you an outline of how I do this and I want to justify why I do it this way.

These are the things I think my students need to know before I go into this explanation:

  • What hormones are
  • What receptors are
  • The definition of homeostasis
  • The role of the glands
  • The bloodstreams role in hormonal distribution
  • The role of the pituitary gland as the master gland
  • The control of blood sugar is also hormonally controlled 
  • The concept of osmosis (but I’m not going to review the whole of the idea, just the basic definition)
  • The role of the kidneys as a filter of the blood

I tend to assess these by using miniwhiteboards and phrasing questions so students have to write as little as possible. So I would ask “what do we call chemical messengers that travel in our blood?” instead of “define the term hormone”

This keeps the pace and the participation ratio high and gives me an indication of what things I need to reteach. I think it is worth the time to quickly reteach or remind students of any gaps that have occured. I won’t do this at the same speed it was initially taught as they will have some prior knowledge, but I might re-draw some simple diagrams from previous lessons or ask the students to note down some answers in writing that they didn’t get right so they can refer back to them later. Depending on the class I might dig a bit deeper and go into hypertonic and hypotonic etc.. especially if they are demonstrating strong prior knowledge. This will just add a little smidge of retrieval practice and demonstrate the links between the two topics in greater detail.

Setting the scene

I always like to go from concrete to abstract and when teaching biology this is often very simple. In this case I am going to use the simple story of what we experience when we urinate in a hydrated and dehydrated state. I am going to make up a simple story of two days. One day when I brought my water bottle into school and another when I forgot it. I used to choose a marathon runner before and after the race as the example, but I found some students would only link dehydration to exercise and not the lack of water consumption. So I now make it more mundane. I do add to the story that part of the day is spent ‘on call’ walking the corridors and stairs etc..

Explaining the science

Apologies for the hand writing. Being left handed and using whiteboards is precarious.

I recorded a version of the explanation section of this lesson last year during lockdown and uploaded it to youtube here.

It’s about 5 mins long and goes through how I dual code my explanation. I spent a bit of time considering how to set out my diagram, partly inspired by Pritesh Riachura’s researchED talk in 2019. I decided to go for a vertical arrangement because I find it easy to compare the left and right from the top and the bottom. I feel the vertical symmetry to the diagram allows students to easily notice the differences and similarities. I chose to draw the organs as boxes and not use a more illustrated approach because I want the students to focus on the relationship between them, not what they actually are. I can see a valid argument for including illustrations, but to me that is not the most important thing right now. They will come across those kinds of images later on in the practice questions.

The one major change I would make now would be to leave the definition until the end of the explanation. That’s the great thing about teaching, always a school day!

At the end of the explanation I get them to copy the diagram into their books so they can refer back to it.

Making them think

After the explanation we will then go into some practice. I really like doing a quick fire verbal quiz of all the pertinent points before I let the students start working through questions. The students have booklets which contain a written description of osmoregulation and a different diagram. Then they have questions. The first questions they have are simple comprehension questions like “What hormone is responsible for controlling osmoregulation?”. These try to break down the concept into all its components so the students have to think about each part specifically. The next set of questions mix prior relevant content, say osmosis or cells, tissues and organs, in with questions that pick apart misconceptions. For these I like a kind of refutation question whereby the students explain why a provided answer is wrong and write the correct version.

The final stage is exam-style questions. These are adapted from past papers and have been edited to either remove unnecessary marks or add more relevant questions to the questions scenario. The last few will be extended response style, with me completing the first one with the class as a worked example. Some of my booklets can be found here.

We make our way through these sections, stopping between each one to check the answers and deal with any concerns. This whole process will probably take about 90 minutes so will most likely take a couple of lessons.

I hope you found that interesting. There is more than one way to teach this well. This is the way I have found most effective.

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