Biology / Unit 10 Bio 2221 short lesson, about 20 seconds
Cephalization
Captions available
The idea
Cephalization concentrates sensory organs and a nerve-cell cluster at an animal's anterior end, a trend associated with bilateral symmetry and directional movement.
In practice
A planarian flatworm's head carries eyespots and a concentrated ganglion, letting it sense its environment before the rest of its body arrives.
Where people slip
Cephalization correlates with directional movement, not with any ranking of a lineage's evolutionary sophistication.
Your place on the trail
Every lesson rests on earlier ones and opens later ones. Tap any to jump.
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