Final answer:
During embryonic development, the stage where unique cell layers develop into tissues and organs is called gastrulation. This follows the blastula stage and involves the formation of three primary germ layers that will differentiate into various organ systems.
Step-by-step explanation:
Gastrulation in Embryonic Development
During embryonic development, unique cell layers develop into specific groups of tissues or organs during a stage called gastrulation. This pivotal process follows the blastula stage, where a hollow ball of cells called the blastula folds upon itself to form three primary layers known as germ layers. Each germ layer is destined to differentiate into distinct organ systems, a process pivotal for forming the body plan.
The ectoderm gives rise to structures such as the nervous system and skin, the mesoderm develops into muscle cells and connective tissues, and the endoderm forms internal organs like the digestive tract. The process of cell division that leads to the blastula is known as cleavage, and gastrulation soon follows to establish the three germ layers.
The rapid, multiple rounds of division that form the blastula, called cleavage, result in over 100 cells. This blastula then enters gastrulation, which reorganizes these cells into the layers necessary for further development.