Developmental Mechanisms Problem Set

Problem 3: Transition to a 2- or 3-layered embryo

At what stage of animal development do cells first move from the surface of the embryo into the interior, resulting in a two- or three-layered embryo?

A. zygote formation

B. blastulation

C. neurulation

D. gastrulation
Gastrulation begins when the wall of the single-layered blastula begins to invaginate. This invagination, and the subsequent rearrangement of cells creates a multi-layered embryo.

E. metamorphosis

The Biology Project Department of Biochemistry and Molecular Biophysics The University of Arizona Thursday, October 30, 1997
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