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protostome vs. deuterostome

protostome vs. deuterostome: What's the difference?

Protostome and deuterostome are terms for members of major taxonomic groups of animals categorized by how they develop as embryos. In protostomes, the first opening in the embryo becomes the mouth. In deuterostomes, the first opening in the embryo becomes the anus, and the mouth develops later. Proto- means “first” and deutero- means “second.” Protostomes are mostly invertebrates. Deuterostomes include both invertebrates and vertebrates.

[ proh-tuh-stohm ]
  1. any member of the lower invertebrate phyla in which the mouth appears before the anus during development, cleavage is spiral and determinate, and the coelom forms as a splitting of the mesoderm.
[ doo-ter-uh-stohm, dyoo- ]
  1. a mouth that develops separately from the blastopore.
  2. any member of the phyla (Chordata, Hemichordata, Echinodermata, Chaetognatha) in which the anus appears first, developing at or near the blastopore, cleavage is radial and indeterminate, and the mesoderm and coelom form from outgrowths of the primitive gut.

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