SciBlogs

Archive March 2011

bullying – it’s everyone’s problem Alison Campbell Mar 30

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Most of us will have seen still and video images of a disturbing, violent assaut by one Wanganui schoolgirl on another. (And maybe some have wondered, as I did, whether we really needed to see that footage again. And again. And again.) It was a horrible act and one that has been deservedly condemned.

What really got me thinking about society’s responses to this, & other acts of violent, physical bullying that have hit the headlines recently, was the editorial in today’s NZ Herald. Why? Because it seems to be pointing the finger at one particular part of the community – our schools. This is understandable – up to a point! – when, for example, we see bullies ‘stood down’ for a few days and then allowed back to class. But what about this?

The expelling school [on occasions where the perpetrators are expelled] has already failed to give the culprit an environment that makes him or her feel sufficiently dignified to respect the rights of others.

This may, or may not, be correct. But why stop at pointing the finger at schools? Children are in their care for around 6 hours a day, 5 days a week, for about 40 weeks a year. So is it right to sheet the blame home to schools alone? What of the family; the whanau; the community; our wider society? Messages about self-worth and the rights of others need to come from all quarters, and if the school’s actions and expectations aren’t supported by people whose actions and opinions matter to the bully, then frankly whatever happens at school may not make much of a difference. (This is not to say that schools shouldn’t try!)

And in any case I wonder if we aren’t inadvertently giving our young people quite the wrong message here. Remember, there’s more to bullying than physical violence: emotional & mental bullying are also common, and made easier by the pervasive nature of electronic communication. (Hence the actions of Ngaruawahia High School’s principal, who is seeking to ban cell phones from the school – although that won’t stop their misuse outside the premises.)

Now, consider some of the currently popular ‘reality’ shows on prime-time TV. I would argue that they almost normalise a culture of bullying, with ‘weaker’ contestants reduced to tears on a weekly basis. How are schools supposed to deal with bullying, how are children supposed to get the message that bullying – in any form! – is just plain wrong, when such behaviour is presented as part of the evening’s ‘entertainment’?

It’s not just the responsibility of schools. This is everyone’s problem. What’s that saying again? It takes a village [a community] to raise a child.

inspired by science – the next stage Alison Campbell Mar 28

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Last year the NZ Council for Education Research published Inspired by Science (Bull et al. 2010) – a discussion paper intended to promote debate about the future of science education in this country. I found it an interesting paper, although I also thought that it didn’t really address some issues (funding, for example, or the fact that secondary schools these days have to do much more than simply prepare students for university study).

Now we have the next step along this path: the launch of Looking ahead: science education for the twenty-first century via an interactive broadcast on Tuesday 5 April (4-6pm). This report’s been developed by the Prime Minister’s Science Advisory Committee, along with the Royal Society & the Ministry of Science & Innovation. (You can read more, plus register for the launch, here.)

I’ve registered for the event already – when the details of where the event’s being ‘held’ (or at least, where to come to watch it) are available I’ll add them here. I’ll be particularly interested in hearing about how future strategies will mesh with the current, new, curiculum & upcoming changes in assessment standards; how teachers will be supported in delivering any new initiatives – and also, for pointers on how to swing societal attitudes to science around, something that changes in the classroom alone probably won’t do.

And of course, I’ll blog about it after the event – maybe even try ‘live-blogging’, provided I can a) type fast enough & b) manage to pay attention to what’s being said at the same time that I’m writing about it!

A.Bull, J.Gilbert, H.Barwick, R.Hipkins & R.Baker (2010) Inspired by science: a paper commissioned by the Royal Society and the Prime Minister’s Chief Science Advisor. New Zealand Council for Educational Research (NZCER), August 2010

my mother said… Alison Campbell Mar 27

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… not to put beans in your ears. But in the case of our fruit-loop of a burmese cat, Fidget, the operative word should have been ‘blowflies’.

About a year before she died, my old dog Bella developed ‘chronic geriatric vestibular syndrome’ - as the name suggests, this is something that often occurs in older dogs, but because it can strike at any age it’s also simply called ‘idiopathic’ vestibular syndrome. It seems to be due to inflammation of the nerves that connect the inner ear with the cerebellum at the base of the brain, thus affecting balance. We knew there was something odd going on as she began to hold her head on one side, but very quickly it got to the point where she was unable to walk and spent her time lying down. And throwing up. As well as the nausea, her fine motor control was shot & she had trouble even drinking.

When – fearing that she’d had a stroke – we rushed Bella to the vet, he said it was more likely the vestibular syndrome & told us to have a look at her eyes. Sure enough, they were flickering all over the place, trying to keep up with the barrage of ‘error messages’ that her brain was receiving from the inner ear. She got over this after a couple of days (though the head tilt remained till the end of her life), so when 13-year-old Fidget recently started the same silly-walk-&-head-tilt thing we assumed it was the same problem.

However, on Friday Fidget was throwing up & walking in circles, so the daughter took her to the vet. ‘Hmmm,’ said the vet, ‘I can understand why you thought it might be vestibular syndrome. But no – when I look into her ear on the affected side I can see….. blowfly eggs & at least one big fat maggot!’ Somehow our cat had got her ears fly-blown! This was both mortifying (in more than one sense) and expensive (because the little toad scratched & bit & required full sedation to have her ears flushed, plus an overnight stay & various meds.)

Fly strike (getting fly-blown) is a common problem for sheep farmers in NZ (& elsewhere). In New Zealand caused by any of four species of fly: the females are particularly attracted by the smell of damp wool - dirty damp wool is even better (from the flies’ point of view). They lay their eggs close to the skin, where it’s nice & moist & the eggs won’t dry out, & once the maggots hatch out they eat first through the skin & then into the underlying tissues, guzzling away until they’re ready to pupate. The wool falls out to reveal exposed flesh & if the animals aren’t treated, they’ll sicken & die as secondary infections take hold.

In Fidget’s case all we can think of is that she’d taken herself off to the gully for a nice nap after breakfast, & a blowfly’s happened past & seen an upthrust ear as a nice oviposition site. It must have been a particularly deep sleep! We’ve often said Fidget has wool between the ears…

(& speaking as the one who’s ended up having to put drops in the cat’s ears, I am extremely grateful that the vet clipped all her claws!)

can ducks count? Alison Campbell Mar 24

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I’m beginning to think there should be 36 hours in a day – I might be able to catch up with things then! Anyway, I was talking with a colleague this evening about a seminar he’d just done with his MSc students, & he said he’d begun with ‘that duck paper’ as it was a session on resource use. I liked that paper when I blogged on it originally, so I thought I’d re-post it to share it with my newer readers.

Of course they can’t – they’re birdbrains! Right?

Ducks certainly don’t have a reputation for being bright. Not like rooks & magpies, or parrots like our own kea, for example. And why would a duck need to count anyway?

Enter optimum foraging theory (& many thanks to Brendan Hicks for putting me onto this one). This behavioural ecology concept predicts that animals looking for food will put in the most effort where they get the best returns i.e. they’ll spend most of their feeding time in areas where there’s the most food. This sounds rather self-evident to us – but how do animals actually know where these areas are? How do they assess food availability? And how good are they at distinguishing between areas with different amounts of food? It’s been known for some time that animals are capable of this (Talbot & Karmer 1986, cited in Kennedy & Gray, 1993):

The remarkable ability of groups of animals to divide themselves rapidly and precisely among two or more feeding sites in proportion to their rate of food delivery results in one of the best matches between theory and observation in contemporary behavioural ecology.

Optimal foraging theory lets researchers study situations where the distribution of resources is known, and make predictions about the distribution of animals using that resource. Ducks are a good subject for such an experiment: they’re common, easy to find and observe – and they love bread :-) The theory predicts that, given two people feeding ducks at different rates, the ducks should be able to calculate which person to go to in order to get the most food. Russell Gray & Martyn Kennedy (1994) tested this with mallard ducks on the Leith River in Dunedin.

They noted that other studies found that animals didn’t always use habitat in the way predicted by optimal foraging theory: they tended to overuse areas with fewer resources and under-use areas with plenty of food. Gray & Kennedy suggested that this might be due to limits in animals’ ability to perceive differences (their ‘perceptual limit’). 

First they got the ducks used to being fed at a particular time of day, so that there would always be around the same number of ducks present. Then they began their test feedings: the researcher at one site delivered food to the ducks 6 times faster than the other researcher 16m away. And they found that overall, more ducks went to the site with the high feeding rate. The relationship wasn’t perfect, suggesting that the ducks weren’t completely accurate in their ability to distinguish which site offered the maximum feeding potential, although it’s also possible that squabbles between the ducks also had an effect on their distribution.

So – ducks aren’t the intellectual giants of the avian world, but they do have some ability to ‘count’.

R.D. Gray & M. Kennedy (1994) Perceptual constraints on optimal foraging: a reason for departures from the ideal free distribution? Animal Behaviour 47: 469-471

M. Kennedy  & R.D. Gray (1993) Can ecological theory predict the distribution of foraging animals? A critical analysis of experiments on the Ideal Free Distribution. Oikos 68: 158-166 

 song chart memes

the discussion you have when you’re really having a discussion Alison Campbell Mar 21

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One of the (many) things I enjoy about teaching is seeing students develop the confidence to take part in discussions & present (& defend) their own views on the topic du jour. Classes where that happens are really seriously enjoyable. And so it was on Friday, when I was in a tutorial class & we were (initially) working on gaining skills in paraphrasing.

This is a key skill that I would like all my first-years to develop. As part of the assessment for this paper, they need to research and write an essay, and when I’m marking I don’t want to see any evidence of plagiarism. So when they find a paper that has informaton that a student would like to use in their essay, they need to a) read for understanding, b) recognise how that material can be integrated with the narrative of their essay, & c) put that information in their own words (with appropriate citations & references, of course!). If they can do that, not only will they be avoiding the pitfalls of plagiarism, but they’ll also have developed a better understanding of the original information & of the wider topic.

But this is a learned skill & needs practice. So for the tut, I presented the class with a couple of selections from recent papers – one from a paper that I & a colleague had published last year, and another on symbiosis (which I’ve written about here). It was the first excerpt that really got things going, so I’ll give you the selected text here & then talk about what happened next:

Since the end of the 19th century there have been public debates in New Zealand that influenced the position of evolution in the science curriculum. In his review of evolution in the New Zealand curriculum, McGeorge (1992) found that as long as the term ’evolution’ was not used in the teaching syllabus it did not seem to present a problem. The explicit inclusion of the term in the senior student syllabus, in 1928, promptly sparked protests that calmed down only when the Department of Education made it clear that ‘evolution’ referred only to ‘physical geography or natural theology’ (p.208). McGeorge concluded that subsequently there were no major problems associcated with the teaching of evolution, apart from the occasional debate, simply because it did “not appear as a specific topic in school biology until Form 7 [equivalent to year 13]” (p.217) and thus did not attract much attention. He cites a member of the New Zealand Creation Literature Society, who said that ”if evolution were dealt with more widely they would push for an even-handed treatment of both evolution and creationism” (p.217).

The 1993 science curriculum (Ministry of Education 1993) did not move much from this position. Evolution gains an explicit mention only in the level 8 (living world) section of the science curriculum, which students encounter in their final year of secondary school (year 13. In fact the 1993 document, while giving evolution as a sample learning context at level 8 (p.68), provides much room for individual interpretation: for a possible learning experience it suggests that students “could hold a debate about evolution and critically evaluate the theories relating to this biological issue”, and that their learning could be assessed by the “ability to select appropriate information … which explore[s] the current theories about evolution” (p.69, emphasis added) (source of excerpt: Campbell & Otrel-Cass, 2010)

Well, the class read this, & talked about it in groups, & then I asked for comment. Interestingly, someone suggested that – quite apart from the various politicking pressure groups – one reason for delaying introduction to the topic of evolution might be that students wouldn’t be capable of the abstract thought needed to deal with some of the concepts, if the subject was introduced much earlier. I was impressed, & said so – plus I could say that this was a viewpoint that the authors of the paper hadn’t considered (lol), but equally that this was not something that appeared to have been taken into consideration by the curriculum planners back in the early-mid 20th century. Someone else countered that students might be able to understand the whole thing better if they were gradually introduced to various supporting ideas over time, which is certainly something that should be happening with the 2007 curriculum iteration. (The cynics among us wondered if it might not simply have minimised the number of students exposed to the concept of evolution, since only a small number of students were progressing to year 13 in the time period under discussion.)

That – plus various paraphrases that were put forward – took care of the first paragraph. So we moved on to the second, which is where things got really interesting as we started to talk about the distinction between acceptance and belief, and about the potential effects of religious faith on attitudes to science, and about the nature of science itself (& why some ‘theories’ are not theories at all, but unscientific/non-scientific propositions). One of the students said that they were really taken with something I said right at the start of the paper, along the lines of “I recognise that you may not all accept evolution as fact & theory, but nonetheless you need to understand it if you’re intending to go on & study biology”. Which led to talk about why I’d used the word ‘accept’, something I’d done quite deliberately: a scientist will ‘accept’ a theory on the basis of the evidence available in support but will still continue to test the bounds of that theory, while the word ‘belief’ tends to have connotations of unquestioning acceptance. I think one of the general conclusions we came to was that science can tell you a lot about how the world works, & while religion’s not very helpful in that regard, for someone of religious faith it can tell you how to live in that world. (This may not satisfy the ‘gnu’ atheists but it is a position that my students were comfortable with.)

And we talked about ‘intelligent design’ and the many problems with this particular viewpoint – for example, its inability to explain how something that’s been ‘designed’ would differ from its ‘undesigned’ alternative; its lack of predictive power; and the paucity of peer-reviewed publications in relevant science journals. Not to mention the clearly theological underpinnings exemplified in the ‘Wedge’ document – here we touched on the whole ‘god of the gaps’ argument.

Eventually we did get back to paraphrasing :-) but it was an interesting & valuable discussion that was respectful of the perspectives of others, and which (among other things) may well have enhanced my students’ understanding of the nature of science.

_______________________________________________________________________________

A discussion that – according to at least one blogger – I never allow my students to have… (i can assure him, such discussions are welcomed & common in my classroom – judging by the tone of his writing & his attitudes to those who hold opposing views, I seriously doubt I could say the same for him.)

A.Campbell & K.Otrel-Cass (2010) Teaching evolution in New Zealand’s schools – reviewing changes in the New Zealand Science curriculum. Research in Science Education 40 (published on-line 21 April 2010). DOI: 10.1007/s11165-010-9173-6

a pat a day may help keep the doctor away Alison Campbell Mar 19

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Poppa’s been in hospital for the last two weeks. Until he was transferred to a hospital closer to his home we were visiting him regularly, but there was one member of the family that he couldn’t have cuddles with, & he really missed that.

And who was he missing? Ben, the little poodle.

Poppa adores Ben, & the little fella seems to know this. He’ll go and lean against the old gentleman’s leg, as Poppa sits in his chair, & be patted for ages. Ben even tolerates spending time perched on a bony elderly knee. (It helps that the dog loves being touched & actively seeks out pats & snuggles.) He’d be an ideal hospital-visiting dog – but not at the big hospital: that’s understandable because there are all sorts of hygiene issues associated with dogs (& other animals) on the wards. But a pity nonetheless.

Luckily there are organisations like CanineFriends that organise hospice and rest-home visits for well-trained pets & owners. And now that I’m aware of them, Ben & I will be signing up. There’s also a considerable body of literature examining the therapeutic benefits of spending quiet quality time with companion animals.

Back in 1996, Beck & Meyers noted that pets were found in 56% of US households. The figures are similar in New Zealand: the Petfood Manufacturers Association tells us that 53% of Kiwi households own a cat (or perhaps that should be, are owned by a cat? - in which case, the fact that we have 3 of the little tyrants makes us seriously downtrodden) & 35% own a dog. Many pet owners may treat their four-legged companions as a member of the family (& I will confess that yes, Ben does sleep at the foot of the bed – along with whichever cat is currently ruling the roost). Cats, dogs, & other domestic pets likely serve a social function – offering a point of common interest in conversation with others (a sort of ‘social lubricant’), or acting as a surrogate family member for someone living alone (Beck & Meyer, 1996; O’Haire, 2009). Plus they accept you uncritically & never answer back! (Although cats can come pretty close!) But there’s also considerable interest in the mental & physical health benefits of living with other species.

The effects of interactions with animals on human health have been studied for more than 30 years; I can remember hearing about one such study when I was still a student at Massey University. For example, O’Haire (2009) cites earlier studies showing that simply watching animals can help reduce anxiety when people are in a stressful situation. Being with a pet dog can apparently reduce cardiovascular and psychological indicators of stress, and watching fish swim around in a tank seems to reduce anxiety – which may be why you will sometimes see fish tanks in doctors’ waiting rooms. Beck & Meyers cited a 1980 report that found pet ownership enhanced the odds of surviving a heart attack, and a more recent study that noted pet owners had reduced blood pressure & plasma cholesterol.

This suggests that pet ownership – regardless of the species of companion animal – may have a positive impact on health costs: O’Haire describes a 1994 Australian study that found that “dog and cat owners had better mental and physcial health than non-owners. They made fewer annual doctor visits and were less likely to be on medication for heart problems and sleeping difficulties”. The author of that study concluded that pet ownership most likely lowered that nation’s spend on health-related services.

Such findings have led to increased interest in the therapeutic use of animals, both in ‘animal-assisted therapy’ (which focuses on specific goals for individual patients) and ‘animal-assisted activities’ (which have no treatment goals). Interacting with a dog, for example, can increase social behaviours like smiling & laughing in patients with Alzheimer’s disease (O’Haire, 2009). Interestingly, such observations go back a long way. Jorgenson (1997) provides a quote from Florence Nightingale, who said that “a small pet is often an excellent companion for the sick, for long chronic cases espectially”.

So when Poppa’s back in his own home we’ll take Ben over as often as we can – & if/when he ends up in long-term care, we’ll be talking with the institution’s managers about the benefits for Poppa (& other residents) of having a small, soft, loving black dog coming in for visits.

A.M.Beck & N.M.Meyers (1996) Health enhancement and companion animal ownership. Annual Review of Public Health 17: 247-257

J.Jorgenson (1997) Therapeutic use of companion animals in health care. Journal of Nursing Scholarship 29(3): 249-254

M.O’Haire (2009) The benefits of companion animals for human mental and physical health. 2009 RSPCA Australia Scientific Seminar

creationist ‘report’ writing: marked down again Alison Campbell Mar 12

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Yesterday I received an e-mail from someone using the pseudonym ‘WinteryKnight, who said:

I was just wondering if you have any recent research publications on experimental biology? I am thinking about writing a blog post comparing you to Michael Behe, and I want to be as fair as possible when I compare your research publications on experimental biology in peer-reviewed journals. Please send me a list of the ones that involve lab experiments, like the Lenski experiments, in an e-mail so I can include and compare it with Behe’s research. I don’t want you to be “Marked Down” unless I find out what you can actually do in the lab.

This sounded a bit like Andrew Schlafly’s demand for Richard Lenski to hand over research data on the evolution of a novel trait in E.coli – although I hasten to add that I’m not in Lenski’s league! (I’m sure all this attention is doing wonders for my blog traffic, though!) In addition, WinteryKnight’s use of the words “Marked Down” made me think he could be another apologist for the Discovery Institute. In any case, I could guess which way this was heading, so I responded:

I don’t think so. I don’t respond favourably to ‘incognito’ requests like this, & I would also expect to be able to view previous posts by the writer to see their approach to the subject.

At which point, WK wrote:

That’s OK, I can use what you have on your web page. Thanks for your reply.

At the time I thought that my response would be quote-mined &/or misrepresented and lo! it has come to pass. (Gosh, I should give up my day job & set up shop as a psychic…) For WinteryKnight hath written… a considerable outpouring of spleen, based on inaccurate &/or sloppy research. I just know this is asking for another quote-mine, but if a student of mine turned out a bit of substandard work like this, their work would indeed be ‘marked down’.

WinteryKnight complains that I don’t appear to have any training in biology. This would be news to those who taught me, including my PhD supervisors at Massey University, and also those who have subsequently hired me to teach – wait for it! - biology. It also suggests a failure to check references, as a simple google search of my name & the phrase ‘PhD Massey’ (from my uni web page) turns up the details of my education. I am indeed a biologist by training (as well as a teacher.) He also complains that I’m not a researcher – before listing a reasonably large number of publications, the majority of which are peer-reviewed. You can’t have it both ways! In addition, he seems unaware that I have also published in the area of teaching evolution in NZ and that I regularly review new biology publications – despite his protestations, I think we can safely assume that I do know what I’m talking about. (By the way, a number of WK’s ‘intelligent design’ references are in the area of cosmology, not evolution. Sorry, WK, but you’d be ‘marked down’ for padding out your references list.)

He also fails in reading comprehension – WK has apparently failed to see my statement (in the comments thread of that original blog post)  that I do encourage discussion of ‘intelligent design’ in classes looking at the nature & philosophy of science. Which is where it belongs. No mechanism, no evidence, special pleading – Not Science.

I would also deduct marks for failing to deliver on what his original brief suggested: Please send me a list of the ones that involve lab experiments, like the Lenski experiments, in an e-mail so I can include and compare it with Behe’s research. Yet I looked in vain for this comparison in WK’s post. Why is that?

Finally, & true to the example of Casey Luskin, it seems that WinteryKnight censors posts to his comments thread. As I said earlier, this is hilariously ironic. So, in the interests of free speech, I attach below comments posted – but not published – at WK’s place and cc’d to me by Grant:

You have contradicted yourself in trying to make out she has no idea what ID is then pointing to references where she has written about ID/creationism. Sloppy, biased reporting. But then what else to expect from someone trying to shore up their beliefs?

Additionally, as she’s not research staff, not it’s meaningful to complain about a lack of ’research’ publications. It wouldn’t have been hard to find that out yourself with a few minutes on google and the university website. You obviously didn’t try.

Her interests are with the school-university interface, as her publications clearly indicate, and those are publications; you can’t pretend they’re not with word games!

’It’s not clear to me that she actually knows any biology at this point.’

Actually, it’s quite obvious she does. You clearly haven’t even tried. In fact, you must have avoided what she wrote in the article that you link to.

’and she refused to give them to me’

Not in the way you’re making out.

& Number8Dave:

What a strange post. Since when was it necessary to be a research biologist to understand evolutionary theory?

I didn’thave time to plough through all the references you copied and pasted, but the first one is an unremarkable piece on echinoderm biochemistry. No mention of Intelligent Design anywhere, though I see it’s partially funded by the Discovery Institute. Presumably the DI aim to quote from this and declare “How could anyone suggest something as complex as this could have arisen by chance?” They, and you, seem incapable of learning that complexity is not something that evolutionary theory has ever had a problem with.

Intelligent Design is not some bold new theory challenging the hidebound evolutionist orthodoxy. It dates back at least as far as William Paley’s Natural Theology in 1802. ID has really not moved beyond Paley in more than 200 years – its proponents still have no mechanism beyond “God did it”, while evolutionary theory has moved ahead in leaps and bounds. We now have a reasonable understanding of how diversity and complexity arise through evolution, although as in any active field there is much still to learn. People such as yourself who reflexively insist that life is too complicated to be natural, and therefore must be supernatural, do nothing but provide amusement and occasional irritation to the rest of us.

another form of donation Alison Campbell Mar 09

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A few days ago my fellow Scibloggers & I had a bit of a discussion around blood donations (as part of a wider discussion of issues relating to the disastrous earthquake in CHristchurch on Tuesday 22 February). While at present the Blood Service isn’t calling for extra donors, I thought I’d write another post on donation anyway – we need 3100 donations each & every week (700 of those in my local region, the Waikato) to keep up with normal demand, & a quick look around those reclining on couches round our local donor centre would indicate that the average donor isn’t getting any younger. So there’s a need for new blood (excuse the dreadful pun) & with the Blood Service on campus this week I thought it would be good to draw attention to that. (And a big ‘thank you!’ to all our students who have gone along to the Rec Centre & rolled up their sleeves for the cause.)

Every blood donation is an act that has the potential to touch a number of lives. My siblings & I were enormously grateful to the unknown donors whose simple, caring act helped provide the blood that improved my mother’s quality of life during her (mercifully brief) battle with cancer. The memory of that is one of the reasons that I became a regular donor myself. And other donors gave the blood that my elderly father-in-law needed as a ‘top-up’ during major surgery earlier this week. (He might actually have ended up with some of my platelets – but of course I’ll never know.)

So, if you’re ever considered the possibility of giving blood – take the next step. Contact the New Zealand Blood Service and talk to them to see if you meet the criteria. At the cost of maybe 30 minutes of your time every 3 months or so (for whole-blood donors) you can make a real difference to the lives of others.

an ancient origin for the human eye Alison Campbell Mar 07

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ResearchBlogging.org

We understand a fair bit, these days, about the evolution of the complex, ‘camera-type’ vertebrate eye. Not that this has stopped creationsists (most recently the ‘intelligent design’ camp as represented by the Discovery Institute) from arguing that the eye is an excellent example of How Evolution Is Wrong – what, they ask, is the use of half an eye? (The answer is, plenty, if an organism can detect the direction of a light source, or the movement of a predator – & in fact it’s been suggested that the evolution of even the most basic photoreceptors may have had a hand in the rapid increase of animal taxa during the Cambrian.)

However, one of the unanswered questions (& thus fertile ground for creationists) has always been, when? Just how deep in time is the origin of the vertebrate eye & its specialised light receptors. A new paper just out may help us to answer that question (Passamaneck et al. 2011).

Passamaneck and his co-workers examined photoreception in larval brachiopods. As a child, I first knew this group of animals by the name ‘lamp shells’, because one of the two shelly valves that encloses the animal’s body looks a bit like an ancient Roman oil lamp. I’ve still got a couple of shells somewhere around – & also a fossil brachiopod endocast, fetchingly called a ‘vulva stone’ because of its apparent resemblance to a portion of the female human anatomy.

Brachiopods are a taxon of marine invertebrates with a reasonably long fossil history – their remains have been found in rocks dating back to the early Cambrian, more than 500 million years ago. Along with the majority of other animal phyla brachiopods are ‘protostomes’: a grouping based on a number of shared embryonic features but named for the fact that when the embryonic gut is forming, the opening that will become the mouth develops first, ahead of the anus. Chordates like us, on the other hand, are ‘deuterostomes’ and yes, you’ve guessed it, the mouth forms after the anus :-)

So, you might expect organisms so different as mammals & brachiopods, seperated by such a gulf of evolutionary time, to have different means of detecting light. According to Passamaneck & his colleagues, you’d be wrong.

Both chordates such as ourselves and the invertebrates (including brachiopods) are bilaterally symmetrical. Passamaneck et al. argue that there is good evidence for “the coexistence of both [ciliary and rhabdomeric] photoreceptor types in the last common bilaterian ancestor” of chordates and invertebrates. (That post of PZ’s that I’ve just linked to gives a really good description of the two types of light detectors in bilaterally symmetrical animals, and the paper I’m talking about takes that work another step forward.) However, scientists have generally thought that only vertebrates’ “cerebral eyes” (ie eyes intimately linked to the brain) use ciliary photoreceptors to detect the direction of light sources, while invertebrates use rhabdomeric receptors for this task. Passamaneck’s team decided to test the hypothesis that protostome invertebrates’ cerebral eyes use only rhabdomeric photoreceptors, using larvae of the brachiopod Terebratalia transversa as a test case. To do this they collected data on the structure & morphology of these eyes, and also on patterns of expression of the relevant genes.

Protostomes do have ciliary photoreceptors, by the way, but up until now it’s appeared that they’re usually found deep in the ’brain’ of protostomes & have non-visual functions ie they’re not involved in detecting light stimuli. However, because the pigments are similar to those expressed in the rods & cones of our eyes, there’s the suggestion of common ancestry. It’s been hypothesised that over time these receptors migrated to the surface of the body & acquired visual functions on the way.

Fully developed, swimming T.transversa larvae have two rows of pigmented spots, described as eye spots, at the anterior end of their bodies. (Younger, non-swimming larvae don’t have them.) The research team determined that these spots are effectively simple eyes made up of 2 photoreceptor cells. One of these cells has a lens-like structure & the other, pigment granules, and both have extensive ciliary membranes positioned between lens & pigment. In addition, each cell of each eyespot is linked by a nerve cell to the larval ‘brain’, which justifies their description as cerebral ‘eyes’. (The ‘brain’ of these larvae is perhaps better described as a cerebral ganglion: a concentration of nerve cells at the anterior end of the animal’s body.) In other words, the researchers found that this protostome species had ciliary photoreceptors on the body surface, rather than the expected rhabdomeric receptors. And this in turn suggests that a key feature of the vertebrate eye, the ciliary receptors that we know as rods & cones, goes back a very long time indeed, to the last common ancestor of protostomes and deuterostomes.

The team went on to look at the expression of a particular gene related to light reception – a c-opsin – cloned from T.transversa. They concluded that this gene was similar to opsins found in other bilaterally symmetrical animals (whether proto- or deuterostome), and that this similarity was due to the groups having shared a common ancestor that also possessed this opsin molecule. And in Terebratalia larvae this c-opsin is expressed in the eyespots, which also supports the idea that they use ciliary photoreceptors. Also, these photoreceptors are definitely used in detecting and responding to directional stimuli: placed in a phototaxis chamber with a light source to one side, swimming larvae moved towards the light source, but went back to a fairly even distribution in the chamber when the light was switched off.

All this led the team to decide that

While ciliary photoreceptors are not the predominant form in the larval cerebral eyes of protosomes, they are found in a phylogenetically diverse range of taxa. It should, therefore, be considered that the use of ciliary photoreceptors in eyes may [possibly] be an ancestral condition for… Bilateria.

In other words, the complex mammalian eye has is evolutionary roots in something akin to the simple eyespots of a tiny marine invertebrate larva.

I wonder what the Discovery Institute will make of that?

Passamaneck YJ, Furchheim N, Hejnol A, Martindale MQ, & Luter C (2011). Ciliary photoreceptors in the cerebral eyes of a protostome larva. EvoDevo, 2 (1) PMID: 21362157

talking past each other? Alison Campbell Mar 06

13 Comments

I’ve spent a bit of time over the weekend, reading through the various posts related to Ken Ring’s attempts to predict future events: here, here, & here, for example. (Yes, really. For once I had a bit of time on my hands & no particular need to do anything else.) I found this a rather chastening experience. Here’s why.

This particular topic (whether or not Mr Ring can do what he claims, and the responses by the media & the scientific community) has generated a fair bit of heat, & it would be fair to say that the heat is on both sides. Scientists & science communicators (often one & the same, at least here on Sciblogs) are concerned that Mr Ring’s ideas get so much air time & are accepted by many. Others, speaking for ‘the public’ (which is an unfortunate term for a highly heterogeneous group whose one common feature is that they are not scientists), feel that the science community is trying to force their views on people & not give opposing views a fair hearing. (And then there are those who come across as ‘anti-science, but I’m not going to address that cohort here.)

And this is what bothers me most. The members of that second group (the ‘others’, above) are not ‘anti-science’. They are doing their level best to tell ‘us’ (the scientists/sci.comms. folk commenting on those threads) how this issue, & our handling of it, is perceived by ‘the public’. The fact that they’ve continued to raise obviously deeply-held objections to ‘our’ point(s) of view means that we’re not really doing a particularly good job of establishing true two-way communication here, & in fact more than once I couldn’t help feeling that I was with two groups of people who, with the best will in the world, were talking past rather than to each other. I worry that we run a real risk of alienating people who are generally supportive of science by giving the impression of dismissing/not listening to their views, at a time when good communication of and about science is probably more important than ever before. Maybe we (i.e. members of both these groups) need to establish the views and understandings we have in common, and then begin to take things further from there?

I shall now duck briefly below the parapet  :-) ….

 

 

…. & emerge again to try to start a discussion here by addressing a point made by Markj on (I think) this thread of Ken Perrott’s. Markj, I think you said that people should be free to make use of all available information to make up their own minds on a problem or topical issue. I agree with you 100% on this. But this raises an immediate question: how do we get all available information out there? There really are issues with getting science into the public sphere (at least some of which relate to existing conceptions about what science is and how it works).  As Sir Peter Gluckman said, how can we ensure that the public has the information necessary to reach a consensus on matters where science has something to contribute? What can all parties do, to get us headed in this direction?

Over to you, folks :-)

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