Chapter 25, Introduction to Animals - Assessment - 25.2 Animal Body Plans and Evolution - Understand Key Concepts/Think Critically - Page 747: 23

In protostomes, the first opening that forms, the blastopore, becomes the mouth whereas the anus forms at the other end as the second opening. In deuterostomes such as chordates and echinoderms, the first opening, the blastopore, becomes the anus whereas the second opening becomes the mouth.

In protostomes, the first opening that forms, the blastopore, becomes the mouth whereas the anus forms at the other end as the second opening. In deuterostomes such as chordates and echinoderms, the first opening, the blastopore, becomes the anus whereas the second opening becomes the mouth.