Question

What is the difference between the embryonic development of protostomes and deuterostomes?

Answer 1

nice question! As you correctly state their differences rest upon the embrionyc development. whats the difference you are wondering. In few words, after fertilization you know the embryo undergoes a series of cell division process, first two, four, eight and so on and so forth. This is called segmentation and this is our first hint to your doubt.
Deuterostomes include groups of animals such as chordates, hemichordates, echinodermates(sea stars and such)...which means these animals undergo a radial segmentation that leaves ultimately the blastopore( just a hole) that will become the anus, the mouth will form later out of an embryonic layer (mesoderm).
the Protostomes are all the rest of animal phyla, in this case the blastopore becomes the mouth directly. ufff