Copyright ? 2011 Pearson Education, Inc. - 1 - Name _______________________ Period ___________ Chapter 47: Animal Development Overview 1. Before beginning this chapter let?s review the basic embryological stages common across a range of animal species. The basic embryological plan is zygote ? cleavage ? blastula ? gastrula ? organogenesis. Explain what each term means and how one stage leads to the next. Zygote: The product of a sperm and an egg fusing (i.e., fertilization) Cleavage: When a series of cell divisions divide or cleave the zygote into a many-celled embryo; typically rapid and lack accompanying cell growth, converting the embryo to a blastula Blastula: A hollow ball of cells that marks the end of the cleavage stage of an early embryo