The Jacobs' lab approach is to first examine genes controlling morphologic changes that evolved during the Cambrian radiation; by comparing genes controlling body plan organization among the classes of molluscs and examining genes responsible for evolution of arthropod limbs. Subsequently the lab will explore a more fundamental issue regarding the molecular organization of the nervous system in invertebrate taxa. Neural organization evolved just before the Cambrian radiation. Evidence indicates that this set of genes controlling nervous system organization was critical to the Cambrian radiation, providing the regulatory interactions in development necessary for differentiation of different cell and tissue types. Once these regulatory interactions evolved in the nervous system they were co-opted for other aspects of body plan organization precipitating the Cambrian radiation.