What marks the end of the pre-embryonic period and the beginning of the embryonic period?
A) implantation
B) the formation of the ectoderm and endoderm in the embryonic disk
C) the formation of the morula
D) the formation of the blastocyst
E) the formation of pharyngeal arches

Question

Quizplus · Accepted Answer

The embryonic period begins with the formation of the three germ layers (ectoderm, mesoderm, and endoderm) in the embryonic disk, marking the transition from the pre-embryonic period.

What Marks the End of the Pre-Embryonic Period and the Beginning