From: "Rich Gauszka" 

Looks like simple organisms have trouble in a mass extinction scenario. On
the plus side - the neocons might be in a bit of trouble 

http://www.newscientist.com/article/dn10652-did-an-ecodisaster-spawn-complex-li
fe.html

The greatest mass extinction of all time led to the proliferation of
complex marine life that quickly dominated the undersea scene, according to
a new analysis of the fossil record.
Palaeontologists have long assumed that ecosystems grew steadily more
complex since the first hard-shelled animals evolved about 540 million
years ago. But Peter Wagner of the Field Museum in Chicago, US, found
something different when he examined data on 1176 marine ecosystems stored
in the massive Paleobiology Database.

The Permian extinction occurred 251 million years ago and wiped out 95% of
marine species. Before this "great dying", simple and complex
marine ecosystems were equally abundant. But afterwards, complex ecosystems
became three times as common - a ratio that has persisted ever since,
Wagner says.

Simple marine ecosystems consist of a few very abundant but stationary
animals, such as crinoids and brachiopods (lamp-shells), which filter food
from the water and leave few resources for less common species, whose
population sizes remain low as a result. Complex ecosystems divide
resources among many more active organisms, such as clams and snails, and
include many more species that interact in complex ways.

"We don't really have a mechanism [to explain the shift]," Wagner
told New Scientist. Other mass extinctions did not change the ratio. But
the end-Permian may have devastated the marine ecosystem so severely
"that basically something new grew in its place", he speculates.

Our modern marine world may never have come into existence if it were not
for the Permian extinction, he adds.

Journal reference: Science, vol 314, p 1254

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