Biology / Unit 10 Bio 2235 short lesson, about 20 seconds
The Cambrian Explosion
Captions available
The idea
The Cambrian explosion names a rapid diversification, beginning roughly 542 million years ago, when most animal body plans appear in the fossil record.
In practice
Cambrian-period fossil sites preserve early arthropod, mollusk, and chordate body plans within a narrow span of time.
Where people slip
"Rapid" here spans millions of years, not instant — the term describes a burst against the longer spans around it.
Your place on the trail
Every lesson rests on earlier ones and opens later ones. Tap any to jump.
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