SciBlogs

Archive January 2011

attitudes towards teaching evolution in the (US) classroom Alison Campbell Jan 31

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ResearchBlogging.org

A little while back I wrote a post on the fact that so-called ‘intelligent design’ is simply creationism by another name, a name intended to obscure the link & to get around the US prohibition on teaching religion in science classes. When this was posted on the NZ Sciblogs site, one commenter said, Firstly, there is nothing to fear, even if it is true. Students can think for themselves, can’t they? I was reminded of this when readinga new article in Science magazine’s Education forum: Defeating creationism in the courtroom, but not in the classroom (Berkman & Plutzer, 2011).

The ‘courtroom’ in the article’s title refers to the Kitzmiller vs Dover case, which followed the decision of the Dover (Pennsylvania) School Board to include materials on ‘intelligent design’ in science classes, and which saw that decision overturned on the grounds that it was effectively requiring teachers to present creationist materials & views in class. This was one more negative outcome for creationism, in a losing streak which has seen attempts to bring creationism into science classrooms thrown out in federal courts for the last 40 years. However, Berkman & Plutzer warn that science may not be winning where it counts most - in the classroom. Collecting data in a US-wide survey of high schoool biology teachers, they found

a pervasive reluctance of teachers to forthrightly explain evolutionary biology.

Can it really be that bad? Well, yes. In the most conservative school districts, around 40% of biology teachers didn’t accept human evolution (c.f. 11% in the least conservative districts), with the outcome that they spend very little time teaching evolutionary biology. On a more hopeful note, the authors estimate that 28% of all high school bio teachers consistently teach evolution using curriculum guidelines recommended by the National Research Council. But another 13% “explicitly advocate creationism or intelligent design by spending at least 1 hour of class time presenting it in a positive light” (Berkman & Pluzter, 2011).

That’s about 40% of bio teachers – what about the other 60%? The ones the authors describe as the “‘cautious 60%’ who are neither strong advocates for evolutionary biology nor explicit endorsers of non-scientific alternatives’? It turns out that these teachers report wanting to avoid stirring up controversy, & also that in many cases they haven’t studied evolutionary biology themselves & so aren’t confident that they can properly answer questions about it in class. Berkman & Plutzer found that in this group there were 3 common strategies for avoiding controversy: a) teaching evolution with reference only to molecular biology, which is an incredibly narrowly-focused approach that avoids dealing with the question of speciation; b) telling students they need to know about evolution for state exams, without aiming for a deeper understanding; & c) going for false ‘balance’ by presenting material from all sides, & letting their students decide what to accept. Which is what my commenter was suggesting; after all, we’re supposed to be encouraging students to think for themselves, aren’t we? What can be wrong with that?

The issue with this is as relevant to science education in New Zealand as it is to the context described by Berkman & Plutzer, and it hinges on the nature and quantity of information that students could be presented with. As Berkman & Plutzer say, is your average teenager really going to read, & assess, the literally thousands of peer-reviewed scholarly articles on the subject of evolutionary biology? And such an approach could run counter to the 2007 NZ science curriculum, because leaving it to students to decide what ‘counts’ & what doesn’t carries with it the message that “well-established concepts like common ancestry can be debated in the same way we debate personal opinions” (Berkman & Plutzer, 2011). Those 3 approaches for treading softly around particular sensitivities are actually going to work against attempts to teach the nature of science. They

undermine the legitimacy of findings that are well-established by the combination of peer review and replication… [and] fail to explain the nature of scientific enquiry.

And no, I don’t think we can sit on our laurels in this area, here in New Zealand. Yes, we have a national curriculum that expects that evolutionary concepts will be introduced to students when they first start primary school. (Having said that, private schools can and do opt out.) But this requires that teachers – at all levels – have the training, resources, & support to teach this material well, to use the opportunity to help students engage with the nature of science, & to handle the inevitable questions when they arise.

And I do hope that we have moved on a bit from 2005, when a Ministry of Education spokesperson told a Herald reporter - talking specifically about evolution – that a “full exploration of these theories should include a consideration of challenges that have been made to them,” and that “challenges to accepted scientific understandings should be considered in science lessons.” 

The problem here, of course, is that a true ‘science controversy’ has science on both sides.

Berkman MB, & Plutzer E (2011). Defeating Creationism in the Courtroom, But Not in the Classroom. Science (New York, N.Y.), 331 (6016), 404-405 PMID: 21273472

(Those interested can find supporting on-line material here, including the questionnaire used by the authors.)

the improbability of an eye Alison Campbell Jan 28

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Because I seem to have very little time on my hands at the moment, I thought I would re-post something I wrote very early on in my blogging career – it hasn’t dated & in fact is quite relevant to a more recent post on ‘intelligent design’ creationism

The camera-type eye of humans (& in fact all vertebrates) is often held up as a classic example of what ‘intelligent design’ (ID) proponentsists (& no, that’s not a slip of the keyboard) call irreducible complexity. The argument goes like this: a) the camera-type eye needs all its parts to function. b) It couldn’t possibly be assembled randomly as Darwinian theory claims. c) The eye thus supports the concept of intelligent design. After all, Darwin himself commented that “To suppose that the eye, with all its inimitable contrivances for adjusting the focus to different distances, for admitting different amounts of light, and for the correction of spherical and chromatic aberration, could have been formed by natural selection, seems, I freely confess, absurd in the highest possible degree” (1859, “On the origin of species”).

 For starters, that comment about evolution occurring through random processes couldn’t be further from the truth, as regular readers will be well aware. But for now – if the ID hypothesis were true, then intermediate stages in eye development would be useless. Darwin recognised this possibility, and countered it by going on to say** that, “if numerous gradations from a perfect and complex eye to one very imperfect and simple, each grade being useful to its possessor, can be shown to exist; if further, the eye does vary ever so slightly, and the variations can be inherited, which is certainly the case; and if any variation or modification in the organ be ever useful to an animal under changing conditions of life, then the difficulty of believing that a perfect and complex eye could be formed by natural selection, though inwuperable to our imagination, can hardly be considered real” (1859, “On the origin of species”).

The eye is a structure that can detect the difference between light & dark (& in many cases colour as well); determine the direction that the light’s coming from; and focus the light to get a sharp image (for people with 20:20 vision, anyway). In other words, it’s a structure that helps us to gather information about our environment. And natural selection can favour an improved ability to gather this information, even in tiny increments, in comparison with other alternatives available at that point in time.

For example, a very basic eye would consist of a few light-sensitive cells, allowing the animal to distinguish light from dark. An individual with a slightly curved ‘eye’, rather than a flat one, could gain some selective adviantage as it would be able to tell what direction the light was coming from. Such functional intermediates do exist in nature: there is a complete series in molluscs, from a flat light-sensitive surface to the complex camera eye of cephalopods. What’s more, eyes have evolved independently in at least 5 other phyla. The lens proteins are the same as, or similar to, existing proteins with other functions, but have been co-opted for a role in vision. (In other words, a key structure in the eye did not have to evolve ‘from scratch’.)

And how long would this take? In a 1994 paper, Nilson & Pelger modelled the eye’s evolution through the continuous small improvements that would be expected, if possession of even the simplest light-sensing organ had a selective advantage. Their most pessimistic estimate for the time it would take to move from a light-sensitive patch to a focussing lens? Less than half a million years. A camera-type eye is indeed an impressively complex structure – but its complexity is certainly not irreducible.

** in the next breath – but creationist quote-miners always leave out the second part of the paragraph, preferring to use how Darwin described a problem but not his solution to it.

D-E.Nilsson & S.Pelger (1994) A pessimistic estimate of the time required for an eye to evolve. Proceedings: Biological Sciences 256(1345): 53-58

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PS one of my readers has provided a link to a nice piece of satire on the subject of intelligent design…

changing the culture of science education at research universities Alison Campbell Jan 24

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ResearchBlogging.org

That’s the attention-grabbing title of a new paper in Science magazine’s ‘education forum’ section (Anderson et al. 2011). Most readers will know that science education is a subject dear to my heart, & a topic that Marcus & I write on from time to time (here & here, for example). The authors are all professors at the Howard Hughes Medical Institute & are supported by that institution to create ‘new programs that more effectively engage students in learning science’ (ibid), so I was keen to see what they had to say on the topic of raising the profile and status of teaching at the tertiary level.

In the opinion of Anderson & his colleagues (& it’s an opinion that I share)

Science education should not only provide broad content knowledge but also develop analytical thinking skills, offer understanding of the scientific research process, inspire curiosity, and be accessible to a diverse range of students.

 Now, you might think, ‘well, obviously!’, and certainly all my colleagues would agree that these are good aims, but the devil’s in the detail. All institutions have what are called ‘graduate profiles’, & ideally when new curricula are being developed, or existing ones reviewed, their relevance to that graduate profile should be at the forefront of everyone’s minds. The difficulty, though, is that most university lecturers aren’t trained teachers but have generally ‘picked it up on the job’. They’re not familiar with the science education literature &, with all the pressures on them to generate external funding and maximise their research profile, it’s going to be hard to take the time to find and read relevant material. Heck, at the moment I struggle to find time, and that’s in my research area!

Anderson et al argue that turning this around requires a culture shift at the level of the institutions themselves, suggesting that these institutions need to “more broadly and effectively recognise, reward, and support the efforts of researchers who are also excellent teachers.” They list 7 initiatives that would move things along towards this end.

Educate faculty about research in learning. There’s a wealth of literature out there on ways to enhance teaching and student learning. (I’m reading some of it myself at the moment.) But the key thing here is time. Without time for researchers in any given discipline to sit down & get a a feel for the education literature (without feeling guilty about not spending that time reading in their ‘own’ field, applying for research grants, supporting research students, or teaching…), & to play around with some of the ideas therein, this will be a long, slow process. Maybe a grassroots approach might be better, more engaging? At my institution we’ve got ‘teaching advocates’ (Marcus is one) who organise informal lunchtime sessions for people to sit down & discuss particular teaching approaches, or maybe just throw ideas around. These are good ways of getting discussions going & supporting people in what they’re doing in the classroom.

Create awards and named rofessorships that provide research support for outstanding teachers. Well, we certainly have awards: in-Faculty & cross-campus at this institution & all others I can think of, plus the national Ako Aotearoa awards. And it’s jolly nice to get one, too! But a question that I’d rather like to look into is, what is the wider impact of these awards? They’re nice for the awardee (in a time when the purse-strings are tight, it’s nice to know that you’ll be able to go to a couple of relevant, conferences without having to think too hard about how to fund it!), but do they change the attitudes & perceptions of others on-campus? Do they have a lasting impact on institutional culture?

Require excellence in teaching for promotion. The authors argue, & I agree, that this needs to be a broad-brush approach, not restricted to looking at data from end-semester course appraisals. They say, “[we] must identify the full range of teaching skills and strategies that might be used, describe best practices in the evaluation of teaching effectiveness (particularly approaches that encourage rather than stifle diversity), and define how these might be used and prioritised during the promotion process.” And as part of this we need to encourage people to try new things. There’s a real worry, & risk, that trying something new in the interests of improving your teaching will backfire: if for whatever reason the students don’t like what you’re doing, those end-semester scores may well decline as a result. Which is why these shouldn’t be the only way of measuring teaching quality and effectiveness. (This, of course, requires that the people involved in determing promotion rounds need to be aware of the existence & value of other means of assessing teaching quality.)

Create teaching discussion groups. the teaching advocate meetings run by Marcus & his counterparts, & the institution’s ‘teaching network’ meetings, are developing a nucleus of such groups. Maybe members of these groups might be interested in working on peer assessment of teaching? You can learn an awful lot from watching other experienced practitioners in action – I know I do. It can be a bit nerve-wracking, having another teacher sit in on your classes, but the discussions afterwards can be really rewarding. (In that regard, something like panopto is an excellent tool to aid reflection on your own teaching, if you’d rather someone else didn’t sit in & give you feedback.)

Create cross-disciplinary programs in college-level learning. Or maybe even just cross-disciplinary discussions. When I taught at high school, everyone was involved in staff meetings, so you had plenty of opportunity to talk with people teaching in other subjects. You tend to lose that sort of collegiality in large tertiary institutions, because every Faculty, & sometimes every department, will have its own tearooms & meeting spots. And that’s a pity, really, because unless you go out of your way to meet your counterparts in other parts of the organisation (or even just go to one of their in-house seminars), you can be closed off from some really interesting discussions about research & practice. (But yes, it is hard to find the time. Time, again; that really does seem central to all this.)

Provide ongoing support for effective science teaching. This can potentially be expensive up-front, but has long-term benefits in terms of student engagement & outcomes. Expensive, because students learn science best when they’re engaged in doing science – & this means lab & field work, as often as not.  But how else are students to learn what it is to ‘do’ science, & to become really engaged in that doing?

And finally, Anderson & his colleagues recomment engag[ing] chairs, deans, and presidents (in NZ, a ‘president’ would be a vice-chancellor), because institutional leadership is crucial in bringing about such changes. These leaders – & in fact, all involved in teaching & learning, need to

foster a culture in which teaching and research are no longer seen as being in competition, but as mutually beneficial activities that support two equally important enterprises, generation of new knowledge and education of our students.

Anderson WA, Banerjee U, Drennan CL, Elgin SC, Epstein IR, Handelsman J, Hatfull GF, Losick R, O’Dowd DK, Olivera BM, Strobel SA, Walker GC, & Warner IM (2011). Science education. Changing the culture of science education at research universities. Science (New York, N.Y.), 331 (6014), 152-3 PMID: 21233371

rules of rational debate Alison Campbell Jan 20

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In my idle moments (haha) I visit a number of different science blogs – both the posts and the comments threads can be educational and entertaining as well. Sometimes, for particular topics (vaccination being one, but anything to do with ‘natural health products’ can almost be guaranteed to set things off as well), the discussion can be derailed by one or two commenters who seem unwilling or unable to follow the normal rules of a rational debate. This can make it really hard to keep a discussion on track & must be frustrating for others trying to follow the thread of ideas.

Anyway, while browsing Peter Bowditch’s Millenium Project I came across a poster encapsulating those rules. I thought I’d share it here, not least because these rules can apply to debate in a classroom just as much as they can to a face-to-face, one-on-one discussion and an internet forum or comments thread. (Click on the graphic for a higher-quality image.) I can see myself applying some of these statements in some of the threads I visit :)

 

the mind’s eye Alison Campbell Jan 18

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I always enjoy reading Oliver Sacks’ books, not least for the wonderful anecdotes but also with the humane, compassionate way in which he described & discusses the various problems that his patients present with. And so I was delighted to get my hands on another one, The Mind’s Eye – as the title suggests, this volume examines the ways in which neurological problems manifest themselves in the way we see the world. One reason the book caught my eye was its cover: red with yellow font – & a font that’s deliberately fuzzy & blurred in places, by way of mimicking how some people see the world. Another reason was that as a child, I remember being fascinated by the question of how other folks perceived colour. I mean, was their ‘red’ the same as the ‘red’ that I saw? And if it was different, how would we actually know, given that we’d both use the same name for the colour of fire-engines & ‘red delicious’ apples. (I didn’t think of traffic lights – there weren’t any in Wairoa when I was a kid.)

The Mind’s Eye set me thinking about that second reason again, because with at least some of the patients he describes, their self-developed coping mechanisms mean that you wouldn’t necessarily know. People without the ability to see in 3-D, for example. This is something that most of us take for granted, & so we assume that everyone else (except, perhaps, those unfortunates who’ve lost an eye to accident or disease) also sees the world in glorious stereopsis. But they don’t; it’s just that in many cases they deal with it in ways that mask what we ’3-D viewers’ would see as a deficiency – & may well have adapted so well that even the possibility of 3-D vision is not attractive to them. And indeed, having monocular vision need not be seen as a handicap: Sacks comments that the first person to fly solo around the world, Wiley Post, did so with only one eye. (The other was removed surgically, following an infection, when Post was in his mid-20s.)

An individual with an uncorrected squint (strabismus) may also lose the capacity for binocular vision, & in the past it was generally thought (based on observations & experiments on other animals) that if a squint wasn’t corrected early in a child’s life, that person would forever after see the world ‘flat’, lacking the depth perception necessary for stereoscopy. But Sacks relates how he received a letter from a neurobiologist, Sue, who’d gone for most of her life in just such a ‘flat’ world after a childhood squint had not been properly corrected. When she was in her late forties, Sue’s sight began to deteriorate and, with the support & advice of a developmental optometrist, had practiced & done exercise after exercise until she acquired the ability to see the world in 3 dimensions. Take a moment & think about how this might feel… frightening? terrifying? wonderful? (It was definitely the latter, in her case.)

Another example Sacks discusses is ‘alexia’, or ‘word blindness’ – the inability to recognise written language, something that is due to damage to a specific part of the brain (say, by a stroke). As someone who reads & writes – copiously! – on a daily basis, both for pleasure & as part of my job, I simply cannot imagine what it would be like to lose this ability. It was something of a relief to read (heh) that at least one of Sacks’ patients was able – slowly and painfully – to recover some of his old skills in this area. A related disorder is ‘prosopagnosia’ – the inability to recognise faces (something that Sacks described in his 1985 book The Man Who Mistook His Wife For a Hat (Yes, seriously, that’s what happened in this particular case study).

Perhaps the most poignant example in the whole book is that of Sacks himself, in an extended essay that combines diary entries with self-reflection following on his diagnosis of a ocular melanoma – a tumour affecting his eye. The details of how the growing tumour encroached on his vision are both fascinating and awful (& if they’re bad to read, think how you would feel to have these things actually happening to you). Surgery to insert a radioactive plaque & subsequent lasering, both targeting the tumour, saw him lose his binocular vision – rather ironical given that Sacks at one point belonged to the New York Stereoscopic Society. Four years later, in 2009, bleeding behind the retina of the affected eye saw him lose almost all sight in it – including his peripheral vision. This meant that he experienced something that hitherto he’d only known through working with patients who’d suffered strokes in a particular region lf the brain – anything, any person, any object, on the affected side effectively ceased to exist for him. As Sacks describes it:

This came home even more forcefully when Kate [his PA] and I finished our walk and headed back to my office. I walked ahead and got into the elevator – but Kate had vanished. I presumed she was talking to the doorman or checking the mail, and waited for her to catch up. Then a voice to my right – her voice – said, “What are we waiting for?” I was dumbfounded – not just that I had failed to see her to my right, but that I had even failed to imagine her being there, because “there” did not exist for me.

Such personal anecdotes make The Mind’s Eye a compelling and affecting read.

O.Sacks (2010) The Mind’s Eye, pub. Picador. ISBN978-0-330-51399-9

resistance to science Alison Campbell Jan 17

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ResearchBlogging.org

One of the topics that comes up for discussion with my Sciblogs colleagues is the issue of ‘resistance to science’ – the tendency to prefer alternative explanations for various phenomena over science-based explanations for the same observations. It’s a topic that’s interested me for ages, as teaching any subject requires you to be aware of students’ existing concepts about it, and coming up with ways to work with their misconceptions. So I was interested to read a review paper by Paul Bloom & Deena Weisberg, looking at just this question.

Bloom & Weisberg conclude that there are two key reasons why people can be resistant to particular ideas in science. One is that we all have ‘common-sense intuitions’ about how the world works, and when scientific explanations conflict with these intuitions, often it’s the science that loses out. The other lies with the source(s) of the information you receive.

And they suggest that ‘some resistance to scientific ideas is a human universal’ – one that begins in childhood & which relates to both what students know & how they learn.

Before they ever encounter science as a subject, children have developed their own understandings about how the world works, based on their own experiences of that world. (This means that they may be more resistant to an idea if it’s effectively an abstract concept & not one that they have experienced – or can experience – on the personal level.) Bloom & Weisberg cite research showing that the knowledge that objects are solid, don’t vanish just because they’re out of sight, fall if you drop them, & don’t move unless you push them, is developed when we are very young children. And we develop similar understandings about how people operate (for example, that we’re autonomous beings whose actions are influenced by our goals) equally early.

Unfortunately for science educators (& communicators!), these understandings can become so ingrained that if they clash with scientific understandings, those particular science facts can be very hard to learn. It’s not a lack of knowledge, but the fact that the students have ‘alternative conceptual frameworks for understanding [these] phenomena’ that can make it difficult (maybe sometimes impossible?) to move them to a more scientific viewpoint. The authors give an example based on the everyday, common-sense understanding that an unsupported object will fall down – for many young children, this can result in difficulty seeing the world as a sphere, because, after all, people & objects on the ‘downwards’ side should just fall right off. And this idea can persist until the age of 8 or 9.

Another example: offered the following diagram, many college undergraduates will pick the ‘common-sense’ option, B over the correct answer, A. Interestingly, in this case, real-world experience can change this – if asked instead about the path of water from a curved hose, most would pick A (Bloom & Weisberg, 2007). (Maybe textbook authors need to think carefully about the analogies & examples that they use to illustrate concepts…)

 

                        Source of image: an on-line modified version of Bloom & Weisberg’s Science paper

And it seems that psychology also affects how receptive people are to scientific explanations. When you’re 4, you tend to view things ‘in terms of design & purpose, which means (among other things) that young children will provide & accept creationist explanations about life’s origins & diversity. Plus there’s dualism: ‘the belief that the mind is fundamentally different from the brain’ (Bloom & Weisberg, 2007), which leads to claims that the brain is responsible for ‘deliberative mental work’ (ibid.) but not for emotional, imaginative, or basic everyday actions. This in turn can mean that, as adults, people can be very resistant to the idea that the things that make us who & what we are, our personality & our very selves, can emerge from basic physical processes. And that shapes how we react to debates around such topics as abortion & stem cell research.

In other words, those who resist the scientific view on given phenomena do so because the latter is counterintuitive, although this doesn’t really explain the fact that there are cultural differences in willingness to accept scientific explanations. For example, about 40% of US citizens accept the theory of evolution – below every country surveyed with the exception of Turkey (Miller et al. 2006). Part of the problem seems to lie with the nature of ‘common knowlege’: if everyone regularly & consistently uses such concepts, children will pick them up & internalise them (believing in the existence of electricity, for example, even though it’s something they’ve never seen). For other concepts, though, the source of the information is important. Take evolution again: parents may say one thing about evolution, and teachers, another. Who do you believe? It seems, according to Bloom & Weisberg’s review of the research in this area, that it all depends on how much you trust the source.

The authors conclude:

These developmental data suggest that resistance to science will arise in children when scientific claims clash with early emerging, intuitive expectations. This resistance will persist through adulthood if the scientific claims are contested within a society, and it will be especially strong if there is a nonscientific alternative that is rooted in common sense and championed by people who are thought of as reliable and trustworthy.

Yet we live in a society where ‘alternative’ explanations are routinely presented by media in a desire to present ‘balance’ where there isn’t any, or indeed, without any attempt at balance at all. And the internet makes it even easier to present non-scientific views of the world in an accessible, authoritative & reasonable way. As science communicators & educators, my colleagues & I really are up against it, & I would say there’s a need for Bloom & Weisberg’s findings to be much more widely read.

Bloom P, & Weisberg DS (2007). Childhood origins of adult resistance to science. Science (New York, N.Y.), 316 (5827), 996-7 PMID: 17510356

J.D.Miller, E.C.Scott & S.Okamoto (2006) Public acceptance of evolution Science 313: 765 – 766. doi: 10.1126/science.1126746 

something old & something new Alison Campbell Jan 12

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Due to popular request (oh, all right, one of my colleagues asked), I thought I’d upload some pictures of the old & new fishponds. Meant to do it when I first wrote about the Great Goldfish Shift but for some reason our VPN server kept cutting me off when I tried to upload the images, & then other things cropped up…

So here’s what the ‘old’ ponds looked like when they first went in, back in 2005 (this is the ‘upper’ pond:

upper pond.jpg

 

And here’s one of the ponds once everything was growing nicely (including the fish population):

upper pond II.JPG

 

The ‘new’ pond has a way to go to reach this state…

new fishpond 1.JPG

 

… but the fish have slowed down on their consumption of pondweed. Now they all turn up with their mouths open at feeding time, prior to acting like sharks in a feeding frenzy :)

We still have to work on getting the plants properly established, though. Please don’t laugh at the soap rack – it was the best we could think of! In the ‘old’ pond there were stepped areas for some of the emergent vegetation to grow in, but that’s not really an option with a bath :)

new fishpond 3.JPG

pesky little hoppers Alison Campbell Jan 09

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With the new house came a long drive lined with agapanthus. My mother would have said, “the dreaded agapanthus”, & she wouldn’t have been far wrong. I don’t like the things very much; they spread very vigorously & I tend to view them as a weed. (I see from Te Ara that Biosecurity New Zealand was looking at calling for a nationwide ban on the plants, back in 2007. I wonder what happened with that? Where we live now, every second house has agapanthus in the garden.) Still, we haven’t really given any thought to what we might replace them with, so the agapanthuses (agapanthi?) have had a reprieve for the moment. And this means that I have to cut back all the spent flowerheads – a bit before they’ve finished flowering, actually, so as to minimise the chances of them setting (& spreading) seed.

This is a bit of a back-breaking job, as it happens, bending down to cut the stems off low. (The Significant Other suggested going hell-for-leather with the pruning shears but that would make an awful mess.) But it’s given me a good view of what’s living in the leaf clumps – & as far as I can tell, it’s mostly passion-vine hoppers (Scolypopa australis. The pesky little things keep flying up & landing on the inside of my glasses & it’s a bit unnerving, I can tell you, to have blurry brown things creeping round in front of your eyes! (For those not familiar with these little beasties, there are some lovely images by Phil Bendle here.)

The adults are about 10mm long, with dark grey-brown bodies & transparent wings supported by a lattice of dark brown veins. The nymphs (juvenile form) are quite different, with creamy white bodies marked with brown spots, and the most wonderful collection of bristles sticking out of their rear ends – reminiscent of an arthropodan shaving brush. Both nymphs & adults feed by inserting long pointed mouthparts (rather like hypodermic needles) into the phloem of plant stems, an efficient if rather vampiric way of getting nutrients as they don’t even have to suck: because phloem is moved around the plant under positive pressure, the animals just have to sit there & breakfast, lunch & dinner simply flow into their guts.

This is quite a cool trick, actually, because the layer of phloem tissue in a stem is very thin, just a few cells thick, & before modern technology came along it was very difficult for an enquiring botanist to insert a needle into the phloem for purposes of measuring flow & nutrient content. This problem was overcome by using aphids, which are also little plant-suckers. Once an aphid had got its mouthparts nicely into the phloem, the scientists wouldcut the insect’s body off just behind its head. The disembodied head remained attached to the plant by its embedded mouthparts, & phloem sap would continue to flow through it for several days.

Because aphids, hoppers & the like are tapping directly into a plant’s nutrient transport system, a heavy infestation can be quite debilitating for the plant. (Not that this seems to be the case for our dreaded agapanthi; their growth is revoltingly vigorous.) The female hoppers cut little slits in the stem in which to lay their eggs, thus creating an opening for infection which can result in die-off of the affected parts. And, as with human drug addicts who share needles, as the hoppers move from plant to plant they can spread disease from one feeding station to the next. In other things, they’re not something you want in large numbers in your garden.

I suspect it’s a vain hope that they’ll stay on the agapanthuses & leave our nice new passionfruit vines alone…

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In other news: the goldfish must like their new pond :) There was a lot of piscine hanky-panky going on when I went out to feed them this morning.

plankton & philosophy – and critical thinking Alison Campbell Jan 07

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Grant & I have stumbled across another NZ science blog, planktonandphilosophy (well, he did the stumbling & then pointed me there). We both particularly liked the excellent post on misreporting of statistics on armed bank robberies: if you took the headlines at face value, the number of armed heists soared last year. But this post looks at the actual data & discovers…. drumroll…. that they’ve dropped. Go over there & read the whole story :)

goldfish & duckweed Alison Campbell Jan 05

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Well, our happy expectations of duckweed & waterfern carpeting the top of our nice new goldfish pond have been dashed – the little beggars (fish) scoffed the lot! We’ve restocked with weed from the old pond but somehow I suspect we might be doing that for a while.

Which shows how ignorant I am about goldfish, really. Back at the old house we were removing great handfuls of weed from the top of the pond, pretty much every second day. (The pumpkins grew very well on this.) Same fish, same amount of commercial goldfish food every day. The only difference I can think of is the lack of any real functioning ecosystem, in the sense that until all sorts of invertebrate life colonises the new pond, there isn’t anything other than the weed to supplement our feedings if the fish get peckish between meals. So maybe we’ll just have to feed them more… And keep some weed growing in a separate bucket, as this goldfish afficionado suggests.

I should have looked into it more deeply, really, as it seems that goldfish adore duckweed… (Which just goes to show that data trump personal anecdote every time!)

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