Biology / Unit 1 Bio 0073 short lesson, about 20 seconds
Three Domains of Life
Captions available
The idea
Microbiologist Woese used gene sequences to sort life into three domains — Bacteria, Archaea, Eukarya — replacing an appearance-based scheme.
In practice
Archaea and Bacteria both lack a nucleus and once looked alike, but gene sequences show them as distinct from each other as from Eukarya.
Where people slip
The three-domain scheme is dated to Woese's 1970s work, not fixed for all time — placements can shift.
Your place on the trail
Every lesson rests on earlier ones and opens later ones. Tap any to jump.
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