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Evolution of birds is result of a drastic change in how dinosaursdeveloped by efwegbe erergeer
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Evolution of birds is result of a drastic change in how dinosaursdeveloped |
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The results of the study appeared May 27 in an online edition ofthe journal Nature . "What is interesting about this research is the way itillustrates evolution as a developmental phenomenon," saidArkhat Abzhanov, associate professor at Harvard and studyco-author. "By changing the developmental biology in earlyspecies, nature has produced the modern bird -- an entirely newcreature -- and one that, with approximately 10,000 species, istoday the most successful group of land vertebrates on theplanet." While it's clear simply from looking at the skulls of dinosaurs andmodern birds that the two creatures are vastly different --dinosaurs have distinctively long snouts and mouths bristling withteeth, while birds have proportionally larger eyes and brains -- itwas the realization that skulls of modern birds and juveniledinosaurs show a surprising degree of similarity that sparked thestudy. "No one had told the big story of the evolution of the birdhead before," said Bhart-Anjan Bhullar, a Harvard PhD studentand first author of the study.
"There had been a number ofsmaller studies that focused on particular points of the anatomy,but no one had looked at the entire picture. What's interesting isthat when you do that, you see the origins of the features thatmake the bird head special lie deep in the history of the evolutionof Archosaurs, a group of animals that were the dominant,meat-eating animals for millions of years." To tackle the problem, the researchers turned to an unusualmethodology. Using CT scanners at Harvard and The University ofTexas at Austin, they scanned dozens of skulls, ranging from modernbirds to theropods -- the dinosaurs most closely related to birds-- to early dinosaur species. By marking various"landmarks" -- such as the orbits, cranial cavity andother bones in the skull -- on each scan, researchers were able totrack how the skull changed shape over millions of years. Tim Rowe is a director of The University of Texas High-ResolutionX-Ray Scanning Facility, where some of the scans were performed,and study co-author.
"We examined skulls from the entire lineage that gave rise tomodern birds," Abzhanov said. "We looked backapproximately 250 million years, to the Archosaurs, the group whichgave rise to crocodiles and alligators as well as modern birds. Ourgoal was to look at these skulls to see how they changed, and tryto understand what actually happened during the evolution of thebird skull." What the researchers found was surprising -- while early dinosaurs,even those closely related to modern birds, undergo vastmorphological changes as they mature, the skulls of juvenile andadult birds remain remarkably similar. In the case of modern birds, Abzhanov said, the change is theresult of a process known as progenesis, which causes an animal toreach sexual maturity earlier. Unlike their dinosaurian ancestors,modern birds take dramatically less time -- just 12 weeks in somespecies -- to reach maturity, allowing birds to retain thecharacteristics of their juvenile ancestors into adulthood.
Ultimately, Abzhanov said, the way the bird skull evolved --through changes in the developmental timeline -- highlights thediversity of evolutionary strategies that have been used overmillions of years. "That you can have such dramatic success simply by changingthe relative timing of events in a creature's development isremarkable," he said. "We now understand the relationshipbetween birds and dinosaurs that much better, and we can say that,when we look at birds, we are actually looking at juveniledinosaurs." "It shows that there's so much for evolution to actupon," Bhullar agreed. "When we think of an organism,especially a complex organism, we often think of it as a staticentity, but to really study something you have to look at its wholeexistence, and understand that one portion of its life can beparceled out and made into the entire lifespan of a new, and inthis case, radically successful organism." Other institutions participating in the study include UniversidadAutonoma de Madrid, Spain; New York College of Osteopathic Medicineof the New York Institute of Technology; and the American Museum ofNatural History. I am a professional writer from General Industrial Equipment, which contains a great deal of information about waterproof duffle bag , waterproof duffle bags, welcome to visit!
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