In examining an unknown animal species during its embryonic development, how can you be sure what you are looking at is a protostome and not a deuterostome?
A) There is evidence of cephalization.
B) There is a well-developed coelom.
C) The animal is triploblastic.
D) The animal is clearly bilaterally symmetrical.
E) The mouth develops first, and the anus develops later.

Question

Quizplus · Accepted Answer

One of the main distinguishing features between protostomes and deuterostomes is the way in which the mouth and anus develop during embryonic development. In protostomes, the mouth develops first from the blastopore, while in deuterostomes, the anus develops first and the mouth forms later from a secondary opening. Therefore, if the animal species being examined has a mouth that develops before the anus, it is likely a protostome.

In Examining an Unknown Animal Species During Its Embryonic Development