Biology / Unit 14 Bio 3705 short lesson, about 20 seconds
Background Extinction Rate versus Mass Extinction
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The idea
The background extinction rate is the ordinary, long-run species-loss rate; a mass extinction is a far higher rate in a short interval.
In practice
The fossil record identifies past mass extinctions where species disappearance rises sharply above baseline.
Where people slip
Assuming one species' loss signals mass extinction is the error — it needs an elevated rate across many lineages.
Your place on the trail
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