Chapter 17, Problem 2MCQ

Summary Introduction

Introduction:

When the embryo folds up into the gastrula, then the inner layer fuses with the opposite side of the embryo, and forms a tube with two openings. The cylinder of endoderm develops into animal’s digestive tract, where one opening becomes the mouth and the other end becomes anus. In protostomes, the gastrula’s first indention develops into the mouth, and the anus develops from the second opening. In deuterostomes, the first indention becomes the anus and the mouth develops from the second opening.