Stories tagged anatomy

Feb
11
2011
It's Friday, so here's today's Science Friday video. Science Friday
Science FridayCourtesy Science Friday
Today,
"Fleas are admirable jumpers -- a talent that humans have recognized for thousands of years, according to engineer Greg Sutton. Yet, until this week, exactly how fleas propel themselves wasn't understood. Sutton and Malcolm Burrows, of the University of Cambridge, filmed fleas jumping, analyzed flea anatomy, made mathematical models and cracked the flea leap mystery. It's not in the knees."
Jun
10
2009

It will be a brutal fight: No one should expect to emerge unchaffed.
It will be a brutal fight: No one should expect to emerge unchaffed.Courtesy Joe Shlabotnik
For years now, members of the robust camp of biologists—paleontologists in particular—arguing that birds evolved directly from dinosaurs have kneeled on the thighs and arms of paleontologists who believe that birds did not evolve from dinosaurs, slapped their scrawny bellies pink, and rubbed dirt and grass in their bifocaled faces. And it was only right—the birds from dino people are bigger, and their veiny biceps ripple with the science of a substantial fossil record, while the clammy palms and toast-rack ribcages of the alternate theory paleontologists positively reek of onions and contrary opinions for the sake of argument. It’s only natural.

I mean, we have fossil impressions of feathers on dinosaurs, analogous bones and body-structures in birds and theropod dinosaurs (theropods, again, are two-legged meat-eaters, like T-Rex, velociraptor, etc.), similar bird-dinosaur proteins (take a look at that last link—Liza listed a bunch of other stories in that post)… the list goes on. Some paleontologists pretty much consider birds to be dinosaurs themselves (little dinos that never went extinct). The book is closed. It’s not even fun beating up on those other paleontologists anymore, because… what’s the point? You wouldn’t beat up on a worm, would you?

Ah, but these worms may have gotten their hands on something soft in this fight, and they’re about to give it a twist…

Check it out—like a hammer from nowhere, or sudden and blatant disregard for the no-scratching rule, the birds-didn’t-evolve-from-dinosaurs people have a new weapon, and they’re back on their feet.

Before we go on, I’m just going to emphasize something real quick here: nobody is saying that birds didn’t evolve, or that they didn’t evolve from something very different from birds as we know them. The question is, from what did birds first evolve, and when?

See, the winning theory is that some theropod dinosaurs began getting smaller and more birdlike in the Jurassic period (with a couple interesting exceptions eventually getting bigger and more birdlike later on, but that’s a different story.) These dinosaurs got little, and feathery, and probably started living in trees, and adapted to leaping, gliding, and eventually flying. By the late Jurassic, we have the archaeopteryx, a feathered, toothed, clawed, and bony-tailed flying machine. By the Cretaceous, there are plenty of pretty normal-looking birds around. Easy-peasy, and there are all those fossils I mentioned before.

“Oh yeah?” say the other paleontologists, “Well what about… this?!” And with that, they flick the back of their hand into the crotch of the unsuspecting bird-dino scientists.

“What are you… aaaaaaahh….” They ask.

Birds, say the alternate theory dudes, don’t have the right legs to be descended from dinosaurs. It’s so obvious, even jerks like you should have seen it.

See, birds need to breath lots of air to be able to fly (it’s hard, I’ve tried). To breath more efficiently, birds have air-sacs in addition lungs. Running all over their bodies (even in their bones) the air-sacs help pump lots of air through the birds' respiratory systems. Fossilized bones appear to show the presence of air sacs in some dinosaur species, too, and this has been seen as further evidence for the bird dinosaur link.

The new argument doesn’t dispute that everybody loves air-sacs. It points out that birds can only move their legs in a very limited way, to keep from collapsing some of their air-sacs when they breath. Birds’ femurs (their thigh bones) are largely fixed—when they walk or run, most of the movement comes from their lower legs. All other walking and running animals—including dinosaurs—have moveable thighs.

This difference, some scientists believe, is great enough that fixed-legged birds couldn’t have evolved from moving-legged dinosaurs. They might have evolved alongside dinosaurs, sharing a common ancestor, possibly one of the thecodonts. Thecodonts were dinosaur-like (but definitely not dinosaurs) and they lived during the Triassic period. Some thecodonts evolved into dinosaurs, and the group died off by the end of the Triassic.

“That’s… all?” says mainstream paleontology, straightening up and cracking its knuckles. “Someone is about to get slapped.”

“…Hiss!” say the other guys, squaring their Gollum-like shoulders.

Until I know a little more about the research, I think I have to side with the traditional birds evolved from dinosaurs argument. The alternative theory folks point out that birds are found much earlier in the fossil record than the dinosaurs they are supposed to have evolved from, but it seems to me that that’s more of a problem of overlap than of a gap—couldn’t later bird-like dinosaurs just be the descendants of the dinosaur-to-bird transitional species? It’s not as if anyone thinks that we look at individuals in the fossil record and say, “ok, you evolved from this one, which evolved from this one” etc. If birds didn’t evolved from dinosaurs like the ones we find from the Cretaceous, then we’re left with a huge gap between thecodonts and archaeopteryx and his pals. And it would have to be some pre-dinosaur thecodont, because I feel like the independent evolution of air-sacs, feathers, and everything else in both lines would be a little too much convergent evolution otherwise.

Plus… I’m not clear on why dinosaurs couldn’t have just evolved to have a fixed leg later on, when they needed more efficient respiratory systems for flying. Their mode of locomotion would have necessarily been changing anyway…

“Hiss!!”

Interesting, though, right?

What do y’all think? Is this ridiculous? Or are we too attached to the mainstream model of bird evolution that we’re unable to keep an open mind to new ideas?

Oct
13
2008

I'm pretty sure its a myth... but why is it that you cannot kiss your elbow?

Aug
10
2007

A shark, doing it's best: Mostly he just wants to be left alone.    (photo by Mshai on flickr.com)
A shark, doing it's best: Mostly he just wants to be left alone. (photo by Mshai on flickr.com)
Scientists in New South Wales and Florida are testing a new method of measuring the biting force of a great white shark using computer models.

Attempts have been made to measure sharks’ biting force underwater, in captivity and in the wild, although these are known to provide inadequate results. Sharks will generally do weak a “test bite” before applying the full force of their jaws, and these test bites are generally all that’s measured.

In this new experiment, researchers are dissecting a 2.4-meter long great white shark, in part to make an extremely accurate computer model of its anatomy, and in part to drive home the point that the animal should have just allowed them to measure its bite while it was alive. Advanced computing methods, originally developed for “calculating stresses in structures such as bridges,” will then be applied to the model, and should provide a much more accurate range of the shark’s biting force.

This process contrasts sharply with my own, I believe, much more elegant test of shark biting power. There are several simple steps involved in my method: Step 1 – gather a variety of small to medium sized objects. Step 2 - Rate the hardness of these objects, not on an objectively quantified scale, but relatively (for example: The kitten is harder than the pillow, but not as hard as the dictionary). Step 3 - Take these objects to your nearest shark. Get the shark to bite the objects (this can be difficult, but the right combination of chum and verbal abuse should do the trick). You will then have a simple and easy to understand scale of shark biting strength (for example: the shark could crush the pillow, the kitten, the dictionary, and the cookie jar, but not the lawn mower engine). If you still feel, at this point, that you need a measurement that uses more universally accepted units, you can then crush similar objects by yourself, far away from the shark, using free weights, or forty-pound bags of dog food. These can then be easily converted into newtons, or pounds per square inch, or whatever your physics teacher requires.

If the computer model method proves to give reasonably accurate results, I suppose it will then be up to individual researchers to choose that method or mine. It will just depend on whether someone doesn’t want to get their hands dirty, or if they care about style and integrity.

May
12
2006

Today's Pioneer Press contains a letter to the editor from Ms. Sheila Steiner, of River Falls, Wisconsin. She writes:

"Would an anatomist in the U.S. have been allowed to skin a human body and fill it with plastic, pose it, and put it on display for a viewer fee simply because prior permission had been granted by the now deceased?

I cannot help but wonder how those who knew the living person think and feel about having their former loved one plasticized and on display.

It is reminiscent of an exhibit in Mexico where corpses were taken from graves and displayed to show how they had been preserved through minerals in the Earth.

It deeply troubles and saddens me to know that we have lost respect for the living as well as the dead. And we explain our unethical behavior as "an incredible learning opportunity".

Please skip the Body Worlds exhibit. Use your 20 dollars to feed the hungry or to buy a good anatomy book for a school."

Steiner's is a perfectly legitimate opinion, but what do you think? Whether you're here in the museum, and you've actually seen the exhibit, or you're visiting via the Internet, we want to know what you're thinking and feeling about the Body Worlds exhibit.

Did you find it gross? Beautiful? Disturbing? Fascinating? Moving? A little of each? Tell us about it.

Want to discuss the ethics of it? During the run of the exhibit, we're featuring four experts from our Advisory Committee (a Catholic theologian, a Hmong physician, a medical ethicist, and a body donation program director) to help answer questions and provide perspectives. Paul Wojda, a theology professor at St. Thomas University, is the first in this series. Ask him your questions!