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Mass Extinctions
things to note about Extinction
• Mass extinction vs. background extinction
• † (dagger symbol) next to a name indicates that organism is extinct
Tyrannosaurus rex†• Average “lifespan” of species
End Ordovician
• 445 mya• Intense glacial activity• Sea level changes• Circulation & weather
disruptions• 85%, but no major
groups
Late Devonian
• 376 mya• Global cooling• 70-82% gone
End Permian (Permo-Triassic)
• 250 mya• 90-95% eliminated
End Triassic
• 200 mya• 76% gone
K/T• 65 mya• 60% lost
A final thought…
Approximately 99.99% of everything that has ever lived on Earth, over the past 3.6 billion
years, is now extinct.
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