| A | B |
|---|
| Zygote | fertilized egg |
| Cleavages | successive mitotic cell divisions without cell growth between cycles |
| Blastula | a hollow ball of cells surrounding a cavity called the blastocoel |
| Gastrula | as the blastula is 'punched in' the embryonic tissue layers will form |
| Ectoderm | the outer tissue layer |
| Endoderm | the inner tissue layer |
| Blastopore | the opening into the gastrula;, it will become the mouth in protostomes and the anus indeuterostomes |
| Archenteron | the blind pouch formed by gastrulation |
| Larvae | an immature body form distinctly different from the adult stage |
| Metamorphosis | the change from larvae to adult body form |
| Hox genes | a unique homeobox-containing family of genes that play important roles in development |
| Radial symmetry | an organism if cut through the central axis produces mirror images |
| Bilateral symmetry | animals that have a right and life side if cut through a center plane |
| Cephalization | the concentration of sensory equipment at one end of the organism |
| Acoelomates | no body cavity between alimentary canal and outer body wall |
| Pseudocoelomates | Animals with three tissue layers with a cavity formed from the mesoderm and the endoderm |
| Coelomates | have a body cavity filled with fluid and separates the animal's digestive tract from the outer body wall which is formed from the mesoderm tissue |
