While working through a practice test for my final exam in an introductory organism biology course, I came across this question:
Protostome characteristics include which of the following?
a) a mouth that develops secondarily, and far away from the blastopore
b) coelom formed by schizocoely
c) radial body symmetry
d) spiral cleavage
e) none of the above
After reading the answers a few times over, I just moved on because I couldn't figure out how to answer. My first instinct said that both (b) and (d) were correct, but the answer is (e).
After some thought, I've come to a few ideas how this could be true.
1. The wording is incorrect, the definition he provides for protostomia says "body cavity formed by schizocoely," and "spiral determinate cleavage."
2. These two characteristics are not present in all protostomes (i.e. spiralia evolves after ecdysozoa, and platyzoa have no body cavity).
Just looking for some clarity or closure regarding this.