The evolutionary trend toward concentrating nervous system structures and sensory organs at the anterior (head) end of an animal. This process results in the formation of a distinct head region with a brain or cerebral ganglion.
Derived from Greek 'kephalē' meaning 'head' plus the suffix '-ization' indicating a process. The concept was formalized in the late 19th century as biologists recognized this as a major evolutionary trend across animal phyla.
Cephalization is why we instinctively know which end of a worm is the 'front' - animals literally put their best sensors forward! This trend is so fundamental that even simple animals like planarians show it, concentrating their primitive 'brain' and eyespots at their leading edge.
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