During embryogenesis, the separation of cells into the three individual germ layers first occurs during which of the following?

Which of the following defines the process by which the entry of one sperm into an oocyte prevents other sperms from fertilizing the same egg?

During gastrulation, the developing embryo undergoes a reorganization of the cells into a multi-layered organism, with each layer necessary to form distinct parts of the eventual fully-formed organism. Which of these primary layers will ultimately form the skin and the nervous system of the organism?

What is the name of the structure that forms during development when the embryo becomes a fluid-filled ball?

A new species found by scientists exhibits indeterminate cleavage up to the third cleavage. If all of the cells in the embryo are separated and incubated in healthy conditions on their own after the third cleavage, how many organisms will develop?