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People: Astrobiology Graduate Student Directory

Loren Ballanti
Biology
One of the fundamental aims of Astrobiology is to understand the long-term
evolution of a biosphere, using Earth as a model for any world on which life
may develop. However, our picture of terrestrial life's history is obscured
by a lack of primary evidence that spans billions of years, its earliest
paleoecology forever inscrutable. Only since the evolution of metazoans
large enough to be seen, and having developed the ability to secrete
mineralized skeletons, has there been a fossil record of sufficient quality
to illustrate evolution over millions of years.
The most striking feature of this history preserved in stone is the periodic
occurrence of mass extinctions. While species have a finite shelf life and
a constant, background level of extinction persists through time, mass
extinctions are catastrophic events that represent severe and prolonged
disturbance on a global scale. Working with Peter Ward, I study the most
ruinous of these events, the Permian-Triassic cataclysm, a two part disaster
that culminated about 251 million years ago with the demise of over 90% of
marine species and similar estimated losses on land.
While all taxa clearly suffered at this time, the patterns of survival and
recovery reveal a selectivity that is not easily explained away. Thus, I am
doing paleophysiology on a variety of marine invertebrates to try and reveal
the rules of survival across the P/T boundary by demonstrating differential
susceptibility to conditions known to be in play in the late Permian,
particularly hypercapnia. Currently, I seek to explain the decline of
articulate brachiopods relative to their bivalve molluscan counterparts.
While I am consequently probably well characterized as a marine
paleobiologist, such a title fails to capture the essence of myriad related
interests and the proper context for thinking about life.
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