Fertilization is the "great awakening" of the oocyte. Dr. Jerry Schatten (Dept. of Zoology, Univ. of Wisconsin-Madison), has likened fertilization to the classic fairy tale, "Sleeping Beauty", since the oocyte is "awakened" from "slumber" by the events of fertilization, resulting in the process of egg activation. Taken in its complete context, fertilization accomplishes at least four things:
Fertilized Xenopus oocytes viewed from the animal pole. After fertilization, the cortical reaction results in modifications to the vitelline envelope, permitting the reorientation of the eggs via gravity. The different densities of yolk in the egg result in the consistent orientation seen here.