AP BIOLOGY

Detailed explanation-1: -Complete answer: Deuterostomia are animals typically characterized by their anus forming before their mouth during embryonic development.

Detailed explanation-2: -The key difference between protostomes and deuterostomes is the fate of the blastopore during their embryonic development. The blastopore in a protostome develops into a mouth, whereas the blastopore in deuterostomes develops into an anal opening.

Detailed explanation-3: -In protostomes, the site of gastrulation is said to give rise to the mouth, while in deuterostomes it forms the anus with the mouth arising from a second opening distant to the site of gastrulation. (A) Phylogenetic relationship of major metazoan groups.

Detailed explanation-4: -In deuterostomy, the developing embryo’s first opening (the blastopore) becomes the anus, while the mouth is formed at a different site later on. This was initially the group’s distinguishing characteristic, but deuterostomy has since been discovered among protostomes as well.

Detailed explanation-5: -During development the mouth of deuterostomes develops from an opening into the embryonic gut other than the blastopore, which develops into the anus. The coelom (a fluid-filled body cavity lined with mesoderm) develops from buds off the embryonic gut. A number of deuterostomes have distinctive larval forms.