1. The embryonic stage where the cells form hollow ball is called blastulation.2. When cells move from the surface of the hollow ball to the interior and form a pore on the surface, it is called invagination.3. The three primary germ layers formed by this cell movement are the endoderm, ectoderm, and mesoderm.4. Ca++ induces membrane-bound vesicles, called cortical granules, to fuse with the plasma membrane in the sea urchin shortly after fertilization.5. In the sea urchin, one function of the fertilization membrane is to block polyspermy.6. When a zygotic cell only partially cleaves and the yolk does not divide, it is called meroblastic cleavage.
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