Last week I described a successful interview lesson and how it evolved over time. This week I’m going to tell you about another interview lesson, only with a different outcome. Before I do that, here’s a photo of the Year 10 Fast Plants…
All planted from seed at exactly the same time on exactly the same day in exactly the same conditions. But one lot has been on the window sill, and one lot has been under the light bank. No prizes for guessing which is which, but as well as the obvious conclusions about plant growth and light, it’s a good exercise for making them think about what they could measure, to make a quantifiable comparison, which they can then link to the difference in treatment.
It’s also a great counter to the nutritionist who believe that there is enough energy in a seed to produce a full grown plant…
Anyway, it’s been an interesting few weeks. I’ve been applying for jobs and have now triumphantly completed a Hat Trick of Rejections. The first two I realised I didn’t particularly want, but you still want to be the one who makes that decision. It’s like when you’re a teenager and you hear that the girl/boy you don’t fancy also doesn’t fancy you. You feel strangely hurt in a completely unreasonable and illogical sort of way.
But the third one I was very keen on. I liked the school, the students, the location, the contract. And I had to teach a lesson to Year 12 on Classification, 5 Kingdoms, 3 domains, and the link between Phylogeny and Classification. In 35 minutes.
So, where to start? I wanted to review their knowledge/understanding of the 5 Kingdoms which they ought to have done at GCSE. A party game? That one where you put a post-it on people’s foreheads and they have to ask questions to figure out who they are? I quickly realised that wouldn’t work – they could simply “get it” by looking at what other people had, rather than asking the kind of questions I wanted to elicit. Quick fire question and answer review? Bit predictable, bit boring… After all, I’m trying to sell myself here, I need to flag up some of my skills…
… but it’s also really important that THEY do something. Figure something out for themselves. What could this be? Well, maybe after reviewing the 5 Kingdoms they could carry out Woese’s analysis themselves? I spend a long time researching this – data on ssrRNA is hard to find – a friend suggests it’s because the key sequences are on different parts of the gene – but I find out all kinds of other really interesting molecular details.
Could they use this to form a classification? And when they’ve done that, could we use it build a phylogeny?
It’s falling together. I have that nice, warm feeling in my tummy which tells me I’ve got something that will work.
So I put it all together, starting with this…
I hope the hyperlinks survive the journey to WordPress!
The idea is that a student selects a colour, any colour. Chance for a bit of banter. Why green? Favourite colour! Why red? Support Liverpool? No? Just like red. OK.
Clicking on the coloured oval takes you to a blank slide. Ask the question – I’m thinking of a type of organism. Here come some clues. Let me know when you can identify it. Then just press the forward arrow.
First clue: cellular. Does that help? No. All organisms are cellular. Does it exclude anything? They might suggest viruses.
Next clue will depend on the organism, but let’s say the student chose red. Second clue is: Cells have internal membranes. Does this help? Ah, now they can exclude the prokaryotes. They know it’s not a bacterium.
Third clue is: Cells have Cell Walls. Does that help? They may jump in with, “It’s a Plant!” Is it? Are you sure? A bit of thought and they realise they can eliminate Animals, but not Fungi or Plants.
Fourth clue is: Sessile. We talk a bit about how this is a really unhelpful feature. It hasn’t moved us on at all.
The fifth clue nails it: Autotrophic. It has to be a Plant.
A final click brings up: Anything else? What else can they tell me about plants? Maybe the cell wall? Right, it’s made of cellulose. And so on.
At this point, click on the smiley green face. It takes you to a picture of an oak tree. Make the point that they didn’t need to see the oak tree to know that it was a plant – they just needed one of its cells…
Clicking on the picture of the oak tree should take you back to the first slide, where the red oval will disappear. Time to pick another.
When they’ve finished these – which will give them Plants, Animals, Fungi and Bacteria – a click from Slide 1 takes them to a picture of a Euglena. What could this be? Any suggestions? Ask some questions! It’s green, which suggests plant. But it hasn’t got a cell wall, which suggests animal. It’s single celled which suggests bacterium, but it’s clearly got internal organelles, so it must be Eukaryote. They will probably recall Protoctista. An Amoeba on the next click reinforces the point that this isn’t a very helpful grouping. What’s so special about being single celled? An Amoeba is an animal in everything but multi-cellularity! And, actually, interestingly, a Euglena has chloroplasts with 3 membranes + thylakoids, which suggests interesting things about its origins (I don’t get round to this in the lesson, but it’s a nice detail to have up your sleeve).
The next slide shows all the organisms in a row. It’s the 5 Kingdoms (my son, Peter, on a water slide, illustrating the Animals). Further clicking reveals their cells. I reiterate: if you know the cell, you know the Kingdom.
The next slide, blank blue, indicates a break in the Powerpoint. Time for them to do some work!
So if we’re comparing organisms at the cellular level, what other points of comparison are there? Apart from being cellular, what do all organisms share? They quickly get DNA, followed by ribosomes and RNA. Which they must have if they’re to make proteins. And how might these vary? We talk about base sequences.
Then I hand out the data table.
As I suspect, this exercise takes them barely 5 minutes, but they’ve grouped 6 unknown organisms into 3 groups. Based on RNA and ribosomal data. Excellent.
On the board, I write LUCA. One of them has heard of the Last Universal Common Ancestor. So how does the family tree look? The line comes up, and then branches. Before the line, what do they all share? AUG as a start codon. But the branch represents an evolutionary innovation. What could have happened? There’s a choice, but maybe it’s the TATA box, or a switch from Formyl-methionine to Methionine. It doesn’t matter. One group (E) goes one way, everything else goes the other way.
And then, at some point, it branches again. A new size of ribosome? More polypeptides in the RNA polymerase? Again, it doesn’t matter, but you now have 2 more groups on two separate branches, sharing a single common ancestor. C on one branch, and A, B, D and F on the other.
Time to break the code. What are these organisms? Back to the Powerpoint and there’s a picture of some Archaea in their pretty thermophilic environment. Because E are the bacteria, C are the Archaea, and A, B, D and F are the Eukaryotes. They can immediately see that the Phylogeny, the family tree, also results in a Classification. We’ve got 3 domains. And tell me about the relatedness. Yes – Archaea are more closely related to us than they are to Bacteria, even though they appear far more simple, even though they are also Prokaryotic, because they share a more recent common ancestor.
I know it’s gone well. The students are interested, involved, curious and asking really good questions. Hurrah!
But I didn’t get the job.
Which is fine. Sort of. Except that I was responding to an advert for a TEACHING post. So I was offering my services as a TEACHER, because I would, ideally, like to move away from the box ticking admin that increasingly occupies my time as a HoD, and back to what I like, what I’m good at. But whatever it was they were looking for, I didn’t fit it. Which puzzles me. There’s lots of things I’m rubbish at: dancing, singing, tennis, DIY, admin., remembering birthdays, growing hair…. but I know I can teach. Am I really not an attractive prospect as a teacher?
Oh well, it was a fun day out. And if nothing else, I have a super new lesson to add to my arsenal.