Biology / Unit 8 Bio 1805 short lesson, about 20 seconds
Cladistics and Clades
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The idea
Cladistics groups organisms into clades, a common ancestor plus every one of its descendants, based on shared homologous traits.
In practice
All descendants of the first amniotic-egg-laying ancestor, including every descendant lineage, together form the clade Amniota.
Where people slip
A clade must include every descendant of its defining ancestor — omitting even one lineage disqualifies the group as a clade.
Your place on the trail
Every lesson rests on earlier ones and opens later ones. Tap any to jump.
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