Final answer:
Gastrulation is the process in which the blastula folds upon itself to form three layers of cells. Neurulation is the development of the nervous system from the neural tube. Spina bifida is a birth defect of the spinal cord related to the incomplete closure of the neural tube.
Step-by-step explanation:
Gastrulation is the process in which the blastula, a ball of cells, folds upon itself to form three layers of cells called germ layers. Each germ layer differentiates into different organ systems. Neurulation, which occurs after gastrulation, is the development of the nervous system from the neural tube.
Spina bifida is a condition related to gastrulation. It is a birth defect of the spinal cord that occurs when the neural tube does not completely close. This results in the emergence of meninges and neural tissue through the vertebral column.