What evolutionary changes were essential to the development of complex body plans? a. mobilityb. internal fertilizationc. tissue and cell differentiation d. body symmetry

The answer is C. This was achieved through gene regulatory networks. The ability of the cells to segment and differentiate gave the metazoans a great advantage. This is thought to have begun in the Cambrian period with complete bodies existing by the Paleozoic era.

answer: substrate concentration. enzymes work best when there is a high enough substrate concentration for the reaction they catalyse.