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: -blastula, hollow sphere of cells, or blastomeres, produced during the development of an embryo by repeated cleavage of a fertilized egg. The cells of the blastula form an epithelial (covering) layer, called the blastoderm, enclosing a fluid-filled cavity, the blastocoel.

Detailed explanation-3: -Blastulation is the stage in early animal embryonic development that produces the blastula. In mammalian development the blastula develops into the blastocyst with a differentiated inner cell mass and an outer trophectoderm.

Detailed explanation-4: -The blastula is a hollow ball of cells organized into an epithelial monolayer. Midway through the blastula stage, the embryo secretes hatching enzyme, which results in proteolytic degradation of the fertilization envelope.

Detailed explanation-5: -A blastocyst is a ball of cells that forms early in a pregnancy, about five to six days after a sperm fertilizes an egg. It implants in your uterine wall, eventually becoming the embryo and then the fetus.