Biology / Unit 8 Bio 1807 short lesson, about 20 seconds
Monophyletic, Paraphyletic, and Polyphyletic Groups
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The idea
A monophyletic group, or clade, includes an ancestor and all its descendants; a paraphyletic group includes only some; a polyphyletic group excludes the ancestor.
In practice
A group built from reptiles alone, excluding birds descended from the same ancestor, is paraphyletic, omitting some descendants.
Where people slip
Only a monophyletic group is a true clade — paraphyletic and polyphyletic groupings do not capture one complete branch.
Your place on the trail
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