Sixty-five million years ago, clouds of ash
choked the skies over Earth. Dinosaurs, along with about half of all the
species on Earth, staggered and died.
But in the seas, a colorful population of
marine bivalves—the group including oysters, clams and scallops—soldiered on,
tucked into the crevices of ocean floors and shorelines. Though they also lost
half their species, curiously,
at least one species in each ecological niche survived.
University of Chicago scientists documented
this surprising trend in a study on extinctions published Jan. 5 in
the Proceedings of the National Academy of Sciences. Though the mass extinction wiped
out staggeringly high numbers of species, they barely touched the overall
"functional" diversity—how each species makes a living, be it
filtering phytoplankton or eating small crustaceans, burrowing or clamping onto
rocks. The same held true for the biggest mass extinction of all, 250 million
years ago: more than 90 percent of all species on Earth died out, but no modes
of life disappeared.
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