Biology / Unit 10 Bio 2285 review, 2 to 3 minutes
Tracing the Protostome-Deuterostome Branch Point
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The idea
This capstone traces how one shared triploblastic, bilaterally symmetrical bilaterian ancestor gave rise to the protostome and deuterostome lineages, following each branch through one representative phylum.
Where people slip
A phylum's adult body plan can obscure its developmental branch — judging a sea star's radial adult form alone, without checking its bilaterally symmetrical larval development and deuterostome mouth formation, would misclassify it as more closely related to a radially symmetrical cnidarian than it actually is.
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