Cloning is one of those things your students might associate with science fiction or futuristic technologies, not something they do in a biology practical, because, well, it doesn’t usually work…until now.
Unlike previous methods used for school practicals, the technique shown in the above video provides a reliable way to carry out the practical that virtually guarantees to produce clones of a cauliflower. It was developed at The Royal Botanic Gardens at Kew to allow scientists to clone plants without needing to be in a sterile lab and it’s already been used to save endangered species.
The key to the success of this technique is the sterile agar growth medium and we’ve made a separate video for technicians showing how to prepare this:
As you know if you’re a regular reader of this blog, we’re big fans of using demonstrations for science teaching and have made a bunch of films about how and why to use them in the classroom. Our latest films are different – they’re about class practicals and we hope they show how these particular practicals could be used to teach specific aspects of Biology, as well as demonstrating how practicals in general might be approached to ensure their effectiveness.
The film above shows various ways to use “algal balls” in Biology practicals – they’re fun to make and a fantastic tool for doing quantitative investigations of photosynthesis. There’s more information and detailed instructions over at the SAPS website.
I’ve just taught Boyle’s Law to my Year 13s and made use of the standard apparatus for demonstrating how volume changes with pressure… only I didn’t use it to do a demonstration. It was a small class, so I thought I’d try something different: I presented the class with the apparatus, told them nothing about it, and challenged them to have a play with it and a) work out what it did, then b) use it to tell me something interesting about how the world works.
The students told me later that they liked the activity because it “made them think” and they seemed to have enjoyed the process of being free to discuss ideas and work together to solve the problem I had set. I think it was a successful activity (although I suspect some students got more out of it than others), however, I wish I could have had more sets of the equipment so they could have worked in even smaller groups or even individually to explore Boyle’s Law. Next year, I might use this – a cheap, ingenious way to allow students to arrive at Boyle’s Law through experimentation:
UPDATE: Since writing this, Bob Worley has been in touch to tell me of a similar approach from CLEAPSS to allow students to explore Boyle’s Law and Charles Law with guidance available here.
I suspect many of you who watch the above video will know exactly how it’s done but it’s not immediately apparent to everyone, especially if you choose to present it in a way that isn’t quite honest about what’s going on.
I use this demo in my teaching to introduce the idea that an object will topple over if the line of action of its weight lies outside its base. I usually present it as a challenge: I start off with two identical (apparently) empty drink cans on my desk (yes, I know the ones in the video have slightly different designs). I offer one of the cans to a student and challenge him or her to balance it on the edge of the base. I tell them I’ll try to do the same with the other can. I make a big show of concentrating, then reveal that I have managed to make my can balance while the student’s can keeps falling over (this usually gets a gasp of approval – as I think the video shows, the can balanced on its edge looks quite disconcerting). After the initial surprise at my being able to balance the can, the students usually guess that something’s not quite right.
I think this demo works well presented as a “magic trick” because it captures students’ attention and provokes the question “what’s going on?” or “how does that work?” and that’s when the discussion begins…
UPDATE: I’ve had a couple of responses to this post on Twitter and elsewhere. I should perhaps have said that using this type of approach may not be suitable for all teachers – you have to be comfortable with the way you present a demo to a class and if showmanship isn’t your thing there’s no point forcing it (although I’d argue that this particular demo requires very little in the way of showmanship to present as a “magic” trick). We touch on this issue in our forthcoming film Demo: The Movie.
A teacher contacted me saying it was a shame I didn’t provide an explanation as it would make it easier for teachers to do the demo if they knew exactly how to do it. So, here’s the trick: place a little water in the can you want to balance before your lesson. The easiest way to judge the correct amount of water is to hold the can in the balanced position then pour water into the can until you feel it just balances. Alternatively, you could pour in liquid wax and let that set so that you have a pre-prepared can that you can keep in the equipment cupboard.