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 cephalisation.
B) The animal is triploblastic.
C) The animal is clearly bilaterally symmetrical.
D) You see a mouth, but not an anus.

Question

Quizplus · Accepted Answer

The presence of a mouth is a characteristic of all protostomes, whereas the anus is formed first in deuterostomes. Therefore, if you see a mouth, but not an anus, it is likely that you are looking at a protostome.

In Examining an Unknown Animal Species During Its Embryonic Development