Final answer:
The ectoderm, or outer layer of an embryo, differentiates into the central and peripheral nervous systems, sensory organs, and the epidermis, which includes hair and nails, not into the endoderm or mesoderm.
Step-by-step explanation:
The ectoderm, which is the outer layer of an embryo, does not become the endoderm or mesoderm, rather it differentiates to form several key structures in the developing organism. Specifically, the ectoderm gives rise to cell lineages that differentiate into the central and peripheral nervous systems, sensory organs, the epidermis, hair, and nails. It should not be confused with the endoderm or the mesoderm, as each of these germ layers has its distinct developmental fates. The mesoderm develops into the skeleton, muscles, connective tissue, heart, blood vessels, and kidneys, while the endoderm forms the epithelial lining of the gastrointestinal tract, liver, pancreas, and lungs.