AP BIOLOGY

Detailed explanation-1: -After fertilization, the zygote undergoes cleavage to form the blastula. The blastula, which in some species is a hollow ball of cells, undergoes a process called gastrulation, in which the three germ layers form.

Detailed explanation-2: -The germinal stage refers to the time from fertilization through the development of the early embryo until implantation is completed in the uterus. The germinal stage takes around 10 days. During this stage, the zygote begins to divide, in a process called cleavage.

Detailed explanation-3: -A zygote undergoes rapid cell divisions (cleavage) to form a spherical ball of cells: the blastula; this will further develop into a blastocyst.

Detailed explanation-4: -Cleavage is a period after fertilization, when a 1-cell embryo starts developing into a multicellular organism. It consists of a series of mitotic divisions, which divide the large volume of a fertilized egg into numerous smaller, nucleated cells-blastomeres. The pattern of cleavage divisions differs between species.

Detailed explanation-5: -Print. Three days after fertilization, a normally developing embryo will contain about six to 10 cells. By the fifth or sixth day, the fertilized egg is known as a blastocyst-a rapidly dividing ball of cells.