The secondary oocyte is released during ovulation. If fertilization occurs, the secondary oocyte nucleus undergoes the second meiotic division, discarding one of its chromosome sets as a second polar body. Sperm activation of egg causes release of corticle granules. In mammals, this hardens the fertilization membrane, blocking sperm from penetrating the fertilization membrane. Either way, additional sperm are blocked from contacting the egg membrane.
Calcium serves as an intermediate between sperm binding and corticle granule activation.
Sexual reproduction follows meiosis and permits new combinations of genes to come toghether in the organism. These are symbols that represent the number of chromosome copies. The ball of cells. Loose cells between hypoplast and epiblast in lower human embryo. One of the first steps is to establish the three germ layers, ectoderm, mesoderm and endoderm.