Biology / Unit 8 Bio 1793 short lesson, about 20 seconds
Branch Points, Basal Taxa, Sister Taxa, and Polytomy
Captions available
The idea
A branch point marks where one lineage split in two; a basal taxon diverged early, unbranched; sister taxa share a point; a polytomy is unresolved.
In practice
Two lineages stemming from one branch point are sister taxa; a branch splitting into three or more marks a polytomy.
Where people slip
Sister taxa share a branch point without descending from each other — a polytomy marks unresolved ties.
Your place on the trail
Every lesson rests on earlier ones and opens later ones. Tap any to jump.
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