Deuterostomes vs Protostomes
As illustrated in this evolutionary lineage, coelomate animals belong to two main groups:
- Protostomes consisting of mollusks, annelids, and arthropods. and
- Deuterostomes consisting of echinoderms and chordates.
In dueterostomes, the zygote divides symmetrically (radial cleavage) and the blastopore becomes the anus.