Posted: 22 Dec 2009 02:37 PM PST
Modern koalas are known for their cuteness, nearly exclusive eucalyptus-leaf diet, and the unexpectedly weird noises they make.
Now, new research into their ancient ancestors shows that the koalas' odd appeal arose through the evolutionary interplay between an increasing reliance on an odd food supply and the need to maintain distinct ear structures for hearing each others' bellows.
By studying the skulls of koala predecessors that lived five to 24 million years ago in the Miocene, an Australian team argues that evolution reshaped the animals faces to enable them to eat the tough leaves while maintaining their specialized communication anatomy.
"The unique cranial configuration of the modern koala is therefore the result of accommodating their masticatory adaptations without compromising their auditory system," write the researchers, led by Mike Archer, a paleontologist at the University of New South Wales, in a paper in the Journal of Vertebrate Paleontology.
The koalas communicate across the Australian forests by making low-frequency calls that are shockingly uncute (listen to the embedded video). The upside to the sounds is that they can travel longer distances — they act like the long waves of AM radio instead of the shorter waves of FM. The researchers hypothesize that the ancient koalas evolved their communication system at a time when the Australian continent was drying out and the koala habitat becoming less dense. By lowering the frequency of their calls, they were able to maintain communication in the sparser forests.
To hear the lower frequencies, they evolved an ever larger apparatus in the middle ear. Modern koala bellows can travel more than 2,500 feet.
Meanwhile, as the Miocene wore on, those same forests were increasingly dominated by the eucalyptus, which became the koalas' main food source. To make use of that resource, though, they had to add chewing power to deal with the tough leaves. And it's that combination of evolutionary quirks that yielded the strange skull of Phascolarctos cinereus, the modern koala.
Citation: "Cranial Anatomy of Oligo-Miocene Koalas (Diprotodontia phascolarctidae): Stages in the Evolution of an Extreme Leaf-Eating Specialization" by Julien Louys, Ken Aplin, Robin M.D. Beck, and Michael Archer in the Journal of Vertebrate Paleontology 29(4):981–992, December 2009
Image: Dorothy Dunphy.
Posted: 22 Dec 2009 11:07 AM PST
<< previous image | next image >>
Not all nuclear reactors are built alike. Power plant designs can vary in their fuels, coolants and configurations, a fact beautifully illustrated by a series of reactor wall charts originally published in issues of Nuclear Engineering International during the 1970s and 1980s.
Since then, the charts have been lovingly collected by Ronald Knief, a nuclear engineer at Sandia National Laboratory. Recently, he completed his collection with help from the Idaho National Laboratory library and began to digitize the drawings. The first eight out of more than 100 have now been permanently archived online by the University of New Mexico libraries.
"This is not a CAD/CAM-type thing," Knief said. "This really is art."
Like the maps that accompanied many issues of National Geographic, the charts were inserts that could be pulled out and tacked up like a poster. They also served as teaching aids for Knief during his tenure at the University of New Mexico, and served to illustrate his books.
"He saved most of them, and it turns out that hardly anyone else saved them, including the publisher," said Donna Cromer, a librarian at the University of New Mexico, who has worked with Knief on the project.
Drawn from reactors built in different nations, the cutaways direct attention to the variety that exists in reactor design. Knief chose these eight as a cross-section of the industry.
"Each of them is representative somewhat of the state-of-the-art version of a particular reactor type," Knief said.
Douglas Point, pictured above, is a boiling-water reactor. In this type of plant, the coolant water flows directly through the fuel, boils and becomes steam, which drives a turbine.
"It's a direct cycle," Knief said, "similar to a standard coal plant."
Boiling-water reactors are a common form of American reactor.
Story via Bibliodyssey
Image: Nuclear Engineering International/University of New Mexico
|You are subscribed to email updates from Johnus Morphopalus's Facebook notes |
To stop receiving these emails, you may unsubscribe now.
|Email delivery powered by Google|
|Google Inc., 20 West Kinzie, Chicago IL USA 60610|