Deuterostomes vs Protostomes
As illustrated in this evolutionary lineage,
coelomate animals belong to two main groups:
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- Protostomes consisting of mollusks, annelids, and arthropods. and
- Deuterostomes consisting of echinoderms and chordates.
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In protostomes, the early embryonic cell divisions are
"angled" (spiral cleavage) and the blastopore (opening in a young embryo) becomes the mouth.
In dueterostomes, the zygote divides symmetrically (radial
cleavage) and the blastopore becomes the anus.
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