You find a clay model of an embryo undergoing gastrulation and realize it must represent a reptile or bird and not an amphibian because
A) a structure on the side of the model is labeled "Dorsal lip of the blastopore."
B) the endoderm cells located at the vegetal pole of the embryo are undergoing involution.
C) cells moving anteriorly from a thickening labeled "Hensen's node" are labeled "Notochordal mesoderm."
D) a region of yolky cells is labeled "Yolk plug."
E) a large central cavity surrounded by endoderm is labeled "Archenteron."

Question

Quizplus · Accepted Answer

The presence of Hensen's node and the movement of cells labeled as notochordal mesoderm indicate that the embryo is undergoing neurulation, which is a characteristic of reptiles, birds, and mammals, but not amphibians. Amphibians undergo a simpler process called neuralation.

You Find a Clay Model of an Embryo Undergoing Gastrulation