Editing Germ layer (section)

== Evolution ==
[[Image:Gastrulation.png|thumb|300px|'''Gastrulation of a diploblast:''' The formation of germ layers from a (1) blastula to a (2) gastrula. Some of the ectoderm cells (orange) move inward forming the endoderm (red).]]

Among [[animal]]s, [[sea sponge|sponges]] show the least amount of compartmentalization, having a single germ layer. Although they have [[Cellular differentiation|differentiated cells]] (e.g. [[Choanocyte|collar cell]]s), they lack true tissue coordination. [[Diploblastic]] animals, [[Cnidaria]] and [[Ctenophora]], show an increase in compartmentalization, having two germ layers, the [[endoderm]] and [[ectoderm]]. Diploblastic animals are organized into recognisable tissues. All [[bilaterian]] animals (from flatworms to humans) are [[triploblastic]], possessing a [[mesoderm]] in addition to the germ layers found in Diploblasts. Triploblastic animals develop recognizable organs.