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August 2010 Archives

A while ago now I discussed how some plants are able to warn others when they're under attack by grazing animals. Now it seems that these responses and interactions are even more subtle - a new paper describes how signalling chemicals in tobacco plants can be altered by the grazers' saliva (Allmann & Baldwin, 2010).

As I described in that earlier post, plants demonstrate a number of responses to grazing. They may produce chemicals that directly harm the grazing animal in some way: poisons, maybe, or substances that inhibit the animal's digestive processes. Other, volatile, chemicals allow communication with other plants - they signal the presence of herbivores and stimulate those plants receiving the signal to produce defensive chemicals in advance of any grazing attack. And it appears that some of these volatiiles can attract predators that in turn feed on the grazers.

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X-rays were discovered in 1895 by Wilhelm Roentgen, a discovery that was to bring him the first Nobel Prize for physics. (No, I'm not really going to trespass on Marcus's territory! Well, not for long.) Like many other scientists of the time, Roentgen was experimenting with electtrifying the thin gases in vacuum tubes. One night he noticed that a fluorescent screen at one end of his lab glowed each time he ran a current through his vacuum tube. The screen continued to glow when Roentgen placed sheets of card, copper, or aluminium between tube & scrreen, but stopped when these were replaced by lead. This must have been startling enough, but he must really have been blown away to see the bones of his hand show up on the screen when his hand passed through the invisible rays emitted from the electrified vacuum tube. Roentgen had discovered X-rays.

Today X-rays are used in a wide range of applications. The structure of DNA was elucidated through X-ray diffraction photographs. Airport security systems use them to detect various proscribed items in travellers' baggage. (Recent developments in this area have led to concerns that customs officers might see more of a traveller than modesty might permit.) And of course there are the medical applications of X-rays, along with their more sophisticated spin-off, the CT (or computerised tomography) scan. CT scans are a signifcant medical tool, but they've also allowed scientists to examine some truly ancient indiviuals: CT scans of a Homo  floresiensis cranium have been used to build a 'virtual endocast' that models the indivdiual's brain & has been used to attempt to determine its affinities.

And where is this heading? Well, I now have a lovely X-ray of my left foot that shows very clearly what happens when your little toe connects at speed with a door jamb. The proximal phalanx of my little toe (that's the toe bone closest to the bones of the foot itself) is in 2 quite distinct parts. Ouchy ouch ouch! I must wear a moon shoe for the next few weeks,and the dog is Not Pleased. Not pleased at all.

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Your immune system is a wonderful, complex, multipartite mechanism that usually allows you to fight off the attentions of the various pathogenic organisms (bacterial, fungal, and viral) that you'll meet during your life. I say 'usually' because it's not always successful on its own, and even where it is, you can be laid low for quite some time - think of flu, but also think of measles, mumps, smallpox, polio... This is where vaccination comes in: this 'primes' your immune system so that it can react far more rapidly when it encounters the actual pathogens themselves. NB for a taste of some 'alternative' thinking on this concept, try this thread over on SciBlogsNZ.

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I have a dog. As a result, papers to do with dogs tend to catch my eye :) On his blog Neuroanthropology, Greg Downey reviews an upcoming book by Pat Shipman and discusses humanity's long relationship with canines. Beginning with the point that "the first animals domesticated were not food sources, but a fellow predator and scavenger: the wolf (dogs being descendants of wolves, even a subspecies by some reckoning). Clearly, domestication wasn’t first about eating the animal..." Our current relationship may have begun as a commensal one, with wolves following nomadic human hunter-gatherers - unfortunately this sort of thing doesn't exactly leave traces in the fossil record. A long post, but well worth reading (especially for those of you currently studying human cultural evolution as part of your NCEA L3 biology).

Jason Goldman writes The thoughtful animal.He's just discussed a paper looking at some intriguing behaviour in the Galapagos marine iguana. These reptiles are non-vocal, communicating among themselves through visual & olfactory signals. But - they appear to respond appropriately to alarm calls by mockingbirds, becoming more vigilant when the birds' calls indicate that a predator's on the prowl. This sort of interspecific eavesdropping's not unknown, but it's a first in a species that doesn't itself use sounds to communicate.

And at Tetrapod zoology, Darren Naish has a fascinating article about the strikingly ugly turtle, the matamata. Its weird looks are matched by its unusual feeding behaviour, for it catches prey not by snatching & biting but by inhaling it, expanding its throat to rapidly draw in large volumes of water along with whatever happens to be swimming in it at the time. How neat is that?

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Parasites are ubiquitous. I remember watching a video (years ago, while I was teaching at secondary school) about parasites that make humans their home. Lice, eyelash mites (yes, really!), various intestinal worms... I tell you, I had psychosomatic itching for days after seeing that! Then I got my hands on Carl Zimmer's wonderful book, Parasite Rex - as well as learning all sorts of stuff about parasites & how they live, I also had it brought home to me that parasites aren't just some sort of passive, undesirable house guest - in many cases they actively influence the host's behaviour in ways that enhance the parasites' ability to complete their life cycles.

I was alerted to a recent paper in this area by a blog post from another Kiwi blogger: his sub-header was 'zombie ants controlled by parasitic fungus for 48 million years', which reall y took my fancy (the link will take you to a story in the Guardian, of which more later in this post). The authors of this paper (Pontoppidan et al. 2010) point out that it's not just a case of the parasite affecting individual ants - they can structure the entire host population in terms of its distribution in time and space & thus influence their own distribuiton: the parasite's 'extended phenotype', if you will.

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On Thursday I was privileged to spend several hours (actually, a lot of the day as we didn't finish until about 8.45pm) judging the Waikato regional science fair. I always enjoy doing this as you get to speak with some wonderful young people who are doing some really good science. (It acts as something of an antidote, especially this year as I'd just written a few posts on pseudoscience -that MMS one among them - and was being to worry about the state of science understanding out there.) These young scientists are passionate about what they are doing and every year I learn something new. F'r instance, I overheard Marcus discussing the finer points of trebuchets with the builder of a modern-day form, & now I know why they were on wheels... 

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funny pictures of cats with captions

Those of you owned by cats will appreciate how accurate this is :)

(From i can haz cheezburger)

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I was reading a couple about 'raw foods' today. This is 'raw foods' as in 'foods that you don't heat above 40oC in processing them.' It's also as in, a vegetarian diet. (I do rather enjoy vegetarian food & when we had a French exchange student staying with us that was pretty much all we ate, because that was what she ate & it must be hard enough being half a world away from home without having to live in a house of voracious carnivores. But I don't think I could eat nothing but, all the time; I like meat too much.) Anyway, what caught my eye wasn't so much the diet program itself but the mis-use of science to promote it. That did rather get my goat brocolli.

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This is a new story & potentially a very exciting one (& I must thank Grant for drawing this story to my attention!). A Nature News item (Petherick, 2010) describes the discovery of green algae apparently living within the cells of salamander embryos. I'll wait with interest for the published paper, but if this finding's confirmed then it will be the first recorded instance of endosymbiosis in a vertebrate.

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There's a lot been written in the blogosphere around what's known as 'complementary & alternative medicine.' (I would argue that there's no such thing - if it works ie improves/cures the patient's health, then it's medicine). In any debate around the use of CAM someone is likely to say that at least it does no harm. For things like homeopathy you could argue that since the client is swallowing only water or sugar pills, with no active principle present, then they're highly unlikely to come to harm (witness the 10-21 homeopathic 'overdose'). The counterargument here is that if the patient relies solely on homeopathy for anything beyond self-limiting conditions then there is in fact considerable potential for harm.

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I've written a couple of times about the so-called 'Miracle Mineral Supplement', aka MMS. A recent post over on Science-Based Medicine looks at some of the claims made for this stuff, which is simply sodium chlorite, 'activated' by being mixed with citrus juice - and at some of the potentially serious side-effects associated with its use. And just now one of my readers has e-mailed me:

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I've been out of the office for a couple of days, with other things on my mind. Unfortunately when this happens there's always a pile of stuff (that needed doing yesterday) waiting on one's desk. So I'm afraid that I might not be in a position to post anything here for the next couple of days. But don't go away - I'll be back :)

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This is a re-posting of something I originally wrote for the 'other blog' - I thought I'd publish it here too as part of the occasional ruminations by Marcus & me on the subject of science teaching :-)

Recently I've had occasion to reflect on the things that have made me the sort of teacher that I am. (Yes, I know there's probably some grammatical issue with that sentence!) So I thought it might be good to write them down - for me, as a way of focusing my thinking, & also because maybe it would elicit other points of view. So, here goes...

I believe that behind every good teacher are a whole lot of other people. In my case the people on my list would include:

  • my parents, who encouraged all their children to follow their dreams & who passed on their own sense of wonder & curiosity about the world around us.
  • the inspirational high-school teachers teachers who not only cemented my love for science but also made me think seriously about the prospect of becoming a teacher myself. Mrs White, Mr Withers, Mr East - I owe you a lot. And my own mother, a teacher herself.
  • the then-Principal of Palmerston North Girls High School, Mrs Calvert: after I finished my PhD, I didn't get a research scientist's job straight away, so I began to look for alternatives. Mrs Calvert looked at a bright shiny new PhD graduate with no formal teaching experience, & must have seen potential there because she offered me a job as a biology teacher. I did my teacher training on the job, extramurally, and settled into the career that I thought I'd left behind when I began my postgraduate studies.
  • all the enormously supportive colleagues with whom I work, & have worked in the past: fellow high-school teachers, academics & the wonderful staff in our Teaching Development Unit, who let me bounce ideas around & give advice on trying new things, supporting me in taking a few risks.
  • my husband & family - thanks, guys! - who've put up with long hours & the seemingly endless piles of marking for quite a long time now.

But ultimately, you can't be a teacher without students. And I've been lucky to have students who don't seem to have minded being guinea pigs (well, not too much!) when I've tried new things, & who've been willing participants in the classroom. And that's been wonderful, because to me the teacher is a learner too, & while my students are (I hope) learning from me, I'm also learning from them.

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Last year's Level 3 paper on 'plant responses & animal behaviour' (AS 90716) had a question on northern rata - rather a lovely tree; I remember that we had one on our section back in Wairoa, when I was a kid. For some reason that tree & the big totara next to it had been left when the rest of the section was cleared.. Anyway, this question began (as all the questions do) with a bit of contextual information:

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There are other photosynthesisers besides Volvox, living in our fishpond. Bigger plants include waterlilies, various sedges, & Elodea. And at this time of year the surface is covered by a carpet of duckweed, but when summer comes the Azolla will tend to take over. Sometimes called 'water fern', Azolla contains an endosymbiont, a cyanobacterium (blue-green alga) that lives within the plant's 'body' but not within its cells (Ran et al. 2010).

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