AP BIOLOGY

Detailed explanation-1: -During neurulation, ectoderm differentiates into two parts. The first is the surface ectoderm, which gives rise to tissues on the outer surface of the body like epidermis, hair, and nails. The second is the neuroectoderm, which forms the nervous system of the embryo.

Detailed explanation-2: -The ectoderm gives rise to the skin and the nervous system. The mesoderm specifies the development of several cell types such as bone, muscle, and connective tissue. Cells in the endoderm layer become the linings of the digestive and respiratory system, and form organs such as the liver and pancreas.

Detailed explanation-3: -The nervous system develops from the ectoderm following an inductive signal from the mesoderm. The initial mesodermal cells condense to form the notochord, which elongates under the primitive streak along the anterior-posterior axis of the developing embryo.

Detailed explanation-4: -The ectoderm is also sub-specialized to form the (2) neural ectoderm, which gives rise to the neural tube and neural crest, which subsequently give rise to the brain, spinal cord, and peripheral nerves. The endoderm gives rise to the lining of the gastrointestinal and respiratory systems.