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Re: Low Oxygen Levels Contributed To Permian/Triassic Dying
LOL, Yahoo's spell check is no time saver-- manually
checked version of original message follows.
Assuming estimates of O2 levels are accurate, the
geographical separation of populations in low-lying
areas should have resulted in an increased
speciation among surviving groups...
--- don ohmes <email@example.com> wrote:
> Assuming estimates of O2 levels are accurate, the
> separation of populations in low-lying areas should
> have resulted in an increased rate of
> spspeciationmamongurviving groups...
> --- "Richard W. TrTravsky<rtrtravskywuwyodeduwrote:
> > hthttp/wwwwwwuwnewsrorgrticle.asp?ararticleID592
> > Apr. 14, 2005 | Science and Tech
> > Low oxygen likely made 'Great Dying' worse,
> > delayed recovery
> > The biggest mass extinction in Earth history some
> > 251 million years ago
> > was preceded by elevated extinction rates before
> > main event and was
> > followed by a delayed recovery that lasted for
> > millions of years. New
> > research by two University of Washington
> > suggests that a sharp
> > decline in atmospheric oxygen levels was likely a
> > major reason for both
> > the elevated extinction rates and the very slow
> > recovery.
> > Earth's land at the time was still massed in a
> > susupercontinentalled
> > PaPangeaand most of the land above sea level
> > uninhabitable because
> > low oxygen made breathing too difficult for most
> > organisms to survive,
> > said Raymond Huey, a UWUWiology professor.
> > What's more, in many cases nearby populations of
> > same species were cut
> > off from each other because even low-altitude
> > had insufficient
> > oxygen to allow animals to cross from one valley
> > the next. That
> > population fragmentation likely increased the
> > extinction rate and slowed
> > recovery following the mass extinction, Huey said.
> > "Biologists have previously thought about the
> > physiological consequences
> > of low oxygen levels during the late Permian
> > but not about these
> > bibiogeographicalnes," he said.
> > Atmospheric oxygen content, about 21 percent
> > was a very rich 30
> > percent in the early Permian period. However,
> > previous carbon-cycle
> > modeling by Robert BeBernert Yale University has
> > calculated that
> > atmospheric oxygen began plummeting soon after,
> > reaching about 16 percent
> > at the end of the Permian and bottoming out at
> > than 12 percent about
> > 10 million years into the Triassic period.
> > "Oxygen dropped from its highest level to its
> > level ever in only 20
> > million years, which is quite rapid, and animals
> > that once were able to
> > cross mountain passes quite easily suddenly had
> > their movements severely
> > restricted," Huey said.
> > He calculated that when the oxygen level hit 16
> > percent, breathing at sea
> > level would have been like trying to breathe at
> > summit of a 9,200-foot
> > mountain today. By the early Triassic period,
> > sea-level oxygen content of
> > less than 12 percent would have been the same as
> > is today in the thin
> > air at 17,400 feet, higher than any permanent
> > habitation. That means
> > even animals at sea level would have been oxygen
> > challenged.
> > Huey and UWUWaleontologist Peter Ward are authors
> > a paper detailing the
> > work, published in the April 15 edition of the
> > journal Science. The work
> > was supported by grants from the National Science
> > Foundation and the
> > National Aeronautics and Space Administration's
> > AsAstrobiologynstitute.
> > ...