Since I was asked what a cnidarian “head” is in reference to this work on multi-headed cnidarians, I’ll answer. In short, they don’t have one.
Pharyngula
Evolution, development, and random biological ejaculations from a godless liberal
Since I was asked what a cnidarian “head” is in reference to this work on multi-headed cnidarians, I’ll answer. In short, they don’t have one.
This is a short video clip of myotome formation in a zebrafish embryo — it’s the subject of an upcoming column in Seed, so I’m putting a short visual aid here.
You can Download the Quicktime movie (620K), or you can watch it via YouTube. Watch closely, it’s short and it flies by!
I’d reconciled myself to the fact that the sun will die in about 5 billion years — time enough to get all the important stuff done, I thought — but now Chris Mims tells me we’ve only got 12 million years. I mean, that’s like going to the doctor, and he says, “Good news, Mr Myers, you’re going to live to be 90” and then he calls you up a little later and says “whoops, little slip up there, you’ve got a month to live.” It’s not good news.
The story is a bit speculative—we’ve long known that there are these very rough periodic extinctions in the fossil record, and now a few wild-eyed theoreticians suggest that it might be correlated with our system’s rotation around the galaxy, and every 60 some million years we swing around to the side that’s getting zapped a little more heavily.
Just to throw a little restraint into the guesswork, though, the mass extinction data shows considerable variability, and also the idea that we’re going to get irradiated is a little excessive. Passage through the rough side of the galaxy would be an event spanning millions of years: the earth was not sterilized in previous events, but if this were the cause, it would mean that there would be a low level increase in radiation over a very long period of time that would have stressed life to varying degrees. We do have 12 million years to manufacture lead-lined umbrellas and try to develop cosmic-ray resistant wheat. I’m just going to have to trust my great600000th-grandchildren to get their act together in time.
High school education makes a difference, but not quite in the way I’d hoped or expected. A recent correlational study looked at the effects of more discipline-specific education at the high school level on grades in college. That is, if a student took heaps of physics as a high school student, how much will it help her in biology, chemistry, and physics? We’d expect that it should help the student perform better in college physics — she has a head start, after all — but one might naively hope that better mastery of a foundational science like physics would also help with chemistry and biology. On the other hand, perhaps bulking up on biology in high school wouldn’t help much at all with physics. Let’s look and find out!
The results are a little disappointing: there isn’t much of a cross-discipline effect at all. You might be a physics wiz in high school, but it doesn’t mean you won’t be floundering in college biology. Here’s the summary chart, which isn’t particularly well-designed, but you can puzzle out the meaning. They looked at performance in three college disciplines, biology, chemistry, and physics, and correlated it with how much high school biology (orange), chemistry (green), and physics (blue) that the students had taken.
Look at the first orange bar. That’s saying that students who had taken a year of biology in high school had a greater than a full grade point advantage over students who had taken no high school biology. A year of high school chemistry gave only a half-point boost in biology, while high school physics only nudged up biology scores a little bit. It’s not just that high school physics is worthless, either — look at the blue bar on the far right. High school physics was as effective at prepping students for college physics as high school biology was at prepping students for college biology. (The middle blue bar for college chemistry is a little troubling: more physics in high school hurts your grade in college chemistry. We shall console ourselves with the immensity of the error bars.)
Oh, and the gray bars in the graph? That’s math. Math is the #1 most effective preparation for doing well in all sciences, across the board; the more math you can get in high school, the better you’re going to do in any science class you might want to take. Look at those giant gray bars — it makes almost a 2-grade point difference to be all caught up in math before you start college. Parents, if you want your kids to be doctors or rocket scientists, the best thing you can do is make sure they take calculus in high school. Please. Failing to do so doesn’t mean your kid is doomed, but I can see it in the classroom, that students who don’t have the math background have to work twice as hard to keep up as the students who sail in with calculus already under their belt.
It’s why that xkcd cartoon to the right is so perfect. (It’s so good it almost — almost — makes up for this one).
Sadler PM, Tai RH (2007) The Two High-School Pillars Supporting College Science. Science 317(5837)457-458.
A few years ago, everyone was in a tizzy over the discovery of Flores Man, curious hominin remains found on an Indonesian island that had a number of astonishing features: they were relatively recent, less than 20,000 years old; they were not modern humans, but of unsettled affinity, with some even arguing that they were like australopithecines; and just as weird, they were tiny, a people only about 3 feet tall with a cranial capacity comparable to a chimpanzee’s. This was sensational. Then on top of that, add more controversy with some people claiming that the investigators had it all wrong, and they were looking at pathological microcephalics from an isolated, inbred population, and then there were all kinds of territorial disputes and political showboating going on, with the specimens taken out of the hands of the discoverers, passed off to a distinguished elderly scientist whose lab damaged them, etc., etc., etc. It was a mess of a story, and the basic scientific issues are still unsettled.
Now the leader of the investigators who found the specimens has written a book, A New Human: The Startling Discovery and Strange Story of the “Hobbits” of Flores, Indonesia(amzn/b&n/abe/pwll), by Mike Morwood and Penny Van Oosterzee. I’m coming to this a bit late — Afarensis reviewed it already this spring — but finally got far enough down in my pile of books to encounter it.
Feeling pragmatic? Is your focus entirely practical, on what works and what will get the job done? Are you one of those fighters for evolutionary biology who waves away all the theory and the abstractions and the strange experimental manipulations, and thinks the best argument for evolution is the fact that it works and is important? This book, The Evolving World: Evolution in Everyday Life(amzn/b&n/abe/pwll) by David Mindell, does make you sit down and learn a little history and philosophy to start off, but the focus throughout is on the application of evolution to the real world. It does a fine job of it, too.
Of course it would be Phil who would remind me: today is the 38th anniversary of the first manned landing on the moon. I remember lying on my stomach on the floor with my chin in my hands, watching TV in the way only 12 year olds can and which would nowadays leave me wondering if I’ll be able to get up again, the front door open, a summer breeze blowing through the screen, the sound of someone down the street mowing their lawns, and right there in front of me, in this ordinary day in a boring little small town, I saw these grainy echos of a human being stepping onto the moon. We can do that. It was hard, and only a tiny few of us have ever accomplished it, but here in our hands and in our minds we have this amazing power to accomplish astonishing things.
How are we going to accomplish our next miracle, do you think?
One of the traditional ways to explain a scientific subject is the historical approach: start at the beginning of the endeavor and explain why people asked the questions they did, how they answered them, and how each answer blossomed into new potential. It’s a popular way of teaching science, too, because it emphasizes the process that leads to new discovery. Middle World: The Restless Heart of Matter and Life(amzn/b&n/abe/pwll), by Mark Haw, exemplifies the technique. Not only is it effective, but this one slim book manages to begin with a simple, curious observation in 1827 and ends up synthesizing many of the major ideas of modern physics, chemistry, and biology!
As a major fan of Natalie Angier, I was well-disposed to favor The Canon: A Whirligig Tour of the Beautiful Basics of Science(amzn/b&n/abe/pwll) — and overall, my opinion of the book is favorable. I’m afraid, though, that it’s filling a very narrow niche and most of my readers here won’t be interested in it…but some of you may find it just right.
You can listen in on George Johnson’s and Sean Carroll’s conversation at Bloggingheads right now. I’m doing this next week with John Horgan, so I should have closed my eyes—Sean is so much prettier than I am.
Don’t let that stop you, though. It’s interesting stuff throughout, and one of the better dialogs I’ve seen on bloggingheads.
