Dramatic shift from simple to complex marine ecosystems occurred 250M years ago at mass extinction

PhysOrg ^ | November 23, 2006 | Field Museum

[SunkenCiv]

The earth experienced its biggest mass extinction about 250 million years ago, an event that wiped out an estimated 95% of marine species and 70% of land species. New research shows that this mass extinction did more than eliminate species: it fundamentally changed the basic ecology of the world's oceans... Specifically, the data and analyses concern models of relative abundance found in fossil communities throughout the Phanerozoic. The ecological implications are striking. Simple marine ecosystems suggest that bottom-dwelling organisms partitioned their resources similarly. Complex marine ecosystems suggest that interactions among different species, as well as a greater variety of ways of life, affected abundance distributions. Prior to the end-Permian mass extinction, both types of marine ecosystems (complex and simple) were equally common. After the mass extinction, however, the complex communities outnumbered the simple communities nearly 3:1.

[Mike Darancette]

The impactor theory for the P-Tr extinction is finding a hard sell these days in favor of climate change due to volcanic out gassing of the Siberian traps. Nova on PBS blamed the extinction on global warming caused by volcanic CO2. Never once did Nova mention attendant cooling caused by volcanic out gassing.

It's quite a coincidence that there is evidence for both impact and volcanism as the cause for at least two of the major mass extinctions (K-T and P-Tr), or is it?

[GoLightly]

Earth is not capitalized.

It's not? So, howcome you capitalized it? ;o)

[SunkenCiv]

Nova on PBS blamed the extinction on global warming caused by volcanic CO2.

Of course -- the global warming demagogues and "Sixth Extinction" demagogues are trying to sell it because they're trying to sell their political agenda. I appreciate what you're saying though:

It's quite a coincidence that there is evidence for both impact and volcanism as the cause for at least two of the major mass extinctions (K-T and P-Tr), or is it?

There really isn't any evidence for massive volcanism at the boundaries, but if there were (and it is often said that there is, such as on that NOVA program), what could have caused it just at those times when mass extinction occurs?

When the iridium abundance in the boundary layers were found to be too high, the previously gradualists started claiming (falsely) that the iridium would be enriched if all the volcanoes on Earth erupted simultaneously and strongly.

The question then, obviously, was what would cause that? :') After that, someone claimed that even a large impact wouldn't cause eruptions anyway.

So that left the impact model standing alone, which is where it still stands. There isn't a viable alternative to it, and the efforts to discredit it is the result of something analogous to what Judge Bork warned of, the political seduction of the sciences.

I think it was the former young turk Robert T. Bakker (of "The Hot-Blooded Dinosaurs" fame) who joined in the non-chorus, claiming that a large impact not only never happened, but also wouldn't cause extinction, and furthermore, that there was no evidence that the mass extinction was even sudden. So there. :')

The defense against the impact model seems to be summed up as, the extinction was already inevitable, and the impact may have happened, but was just a huge coincidence and didn't do anything to the species which went extinct.

[Mike Darancette]

After that, someone claimed that even a large impact wouldn't cause eruptions anyway.

I have yet to hear of a reason for the sudden appearance (concurrent with formation the Snake River Basalt) of what is now the Yellowstone Hot Spot some 17mya, other than an impactor.

[SunkenCiv]

I don't doubt that local volcanism might result from impact, but not worldwide volcanism. :') I just cone accept that. [rimshot!] Magma told me there'd be days like these. [rimshot!]

http://www.freerepublic.com/focus/f-chat/1743929/posts?page=3#3

"He asserted that he has found evidence -- in the form of gravity anomalies and certain rock deposits -- for such an impact in the South Atlantic, in an area where, many scientists believe, South America, Africa, and other land masses fit together in the primordial supercontinent called Gondwanaland. Rampino claims that the gradual breakup of Gondwanaland into present-day continents may have been initiated by the catastrophic impact."

[grey_whiskers]

Interesting question, if this article is correct.

"Broken window" theory does not work in economics, but apparently *can* work in ecosystems.

I have some guesses why, I'd like to get your take on it.

Cheers!

[grey_whiskers]

G.K. Chesterton in his book The Wisdom of Father Brown (originally published in 1929) had as a side topic in one of his short stories the concept of "catastrophism" which seems to touch on this...

"Thus, when a very unobtrusive Oxford man named John Boulnois wrote in a very unreadable review called the Natural Philosophy Quarterly a series of articles on alleged weak points in Darwinian evolution, it fluttered no corner of the English papers; though Boulnois’s theory (which was that of a comparatively stationary universe visited occasionally by convulsions of change) had some rather faddy fashionableness at Oxford, and got so far as to be named “Catastrophism.”"

Cheers!

[night reader]

The earth experienced its biggest mass extinction about 250 million years ago...

Bush's fault!!!

[Dustbunny]

Wow, they were actually able to determine this due to what was found in fossil communities throughout the Phanerozoic. Amazing.

[SunkenCiv]

Ive never been a Phanerozoic, but I still tune in. ;')

[SunkenCiv]

Thanks, that sounds like it may have been a precursor to the late Stephen J. Gould's punctuated equilibrium model, although that was mostly a semantic exercise or spin-doctoring.

[grey_whiskers]

Thanks, that sounds like it may have been a precursor to the late Stephen J. Gould's punctuated equilibrium model, although that was mostly a semantic exercise or spin-doctoring.

Chesterton was an adult convert to Catholicism and an ardent anti-evolutionist ;-)

Odd that you should call Gould's punk-eek "spin-doctoring"; I thought it was a fairly well-supported description of discontinuties in the rate of mutations and/or speciation.

...and as such, might cause problems with a simplified 'DNA clock' method of dating things. :-)

Cheers!

[SunkenCiv]

...and as such, might cause problems with a simplified 'DNA clock' method of dating things.

Well put.

[SunkenCiv]

found a file on the hard drive, called "Punctuated Equilibria":

Evolutionary Dynamics: Models of Extinction
Gunther Eble, Smithsonian Institution, SFI Postdoctoral Fellow
Mark Newman, SFI Research Professor
Kim Sneppen, Niels Bohr Institute
Per Bak, NORDITA, SFI External Faculty
David Raup, Palentology, University of Chicago (Retired), SFI Science Board
Simon Levin, Ecology, Princeton, SFI Science Board

Extinction has played an important role in the development of life on the Earth... It is important first to understand the nature of extinction in the fossil record, before one can undertake any modeling efforts to try to explain that extinction. In recent years a number of claims have been made about apparent trends in the fossil record of extinction which might point to interesting underlying dynamical processes in the biosphere. Stuart Kauffman (biology, Bios, SFI External Faculty), for example, has argued that the distribution of the sizes of extinction events approximately follows a power-law form, taken by some to be indicative of criticality in the processes giving rise to extinction. Sneppen et al. have suggested that the distribution of the lifetimes of genera may also be a power law, and Ricard Sole (ecology, Barcelona, SFI External Faculty) et al. have presented evidence that the power spectrum of extinction intensity during the Phanerozoic has a 1/f form.

[SunkenCiv]

Power Spectra of Extinction in the Fossil Record
M. E. J. Newman and Gunther J. Eble
1998-12

Abstract: Recent Fourier analyses of fossil extinction data have indicated that the power spectrum of extinction during the Phanerozoic may take the form of 1/f noise, a result which, it has been suggested, could be indicative of the presence of "critical dynamics" in the processes giving rise to extinction. In this paper we examine extinction power spectra in some detail, using family-level data from a variety of different sources. We find that although the average form of the power spectrum roughly obeys the 1/f law, the spectrum can be represented more accurately by dividing it into two regimes: a low-frequency one which is well fit by an exponential, and a high-frequency one in which it follows a power law with a 1/f2 form. We give explanations for the occurrence of each of thse behaviours and for the position of the cross-over between them.

[grey_whiskers]

Thanks, more material on the "to read" pile (approx 500 websites and many books to boot). Over the last month I have read "Atlas Shrugged" (Ayn Rand), "The Quark and the Jaguar" (scientific popularization by Nobelist Murray Gell-Mann), "The Scarlet Pimpernel" (classic lit), "Eats, Shoots, and Leaves" (grammar text), "Avalon" (Stephen Lawhead novel), "Patrick", (Stephen Lawhead novel), and "Fahrenheit 451" (Ray Bradbury).

I was on hiatus from FR but am now putting my head back underwater so to speak; but only for a short time.

Cheers!

[colorado tanker]

Your posts take me back to high school biology, where the text gleefully trashed the stupidity of those who subscribed to catastrophism before Darwinian gradualism became the accepted model. I still remember it because I wondered at the time when will the next textbook be written trashing gradualism and making fun of those who believed that. We think we know everything, but there is so much we have yet to learn.

[SunkenCiv]

Never gonna happen until we round up and hang the global warming demagogues and other single party state advocates.

[colorado tanker]

Agreed.

The evo-crevo wars get lots of attention these days, but I'm convinced the advance of junk science in aid of political liberalism is doing serious damage to the reputation of science and scientists among lay people.

[ThanhPhero]

Sounds like a lab experiment ended and a new one began.