Hank explains the way in which organisms grow and develop. He covers how to determine the complexity of an organism and illustrates that the digestive tract is the first part of the organism that develops.

Key Words: Animal Phyla, Layers of Tissue, Zygote, Cleaving, Blastula, Radial Symmetry, Bilateral Symmetry, Gastrulation, Gastrula, Deuterostome, Germ Layers, Ectoderm, Endoderm, Diploblastic, Triploblasts, Mesoderm