AP PSYCHOLOGY

Detailed explanation-1: -The embryonic period is the most critical period of development because of the formation of internal and external structures.

Detailed explanation-2: -Gastrulation is one of the most critical stages of early embryonic development, which takes place between days 14 and 21 after fertilization. During this step, there is an explosion of cell diversification and the different cells get ready to form the specific organs and body tissues later in development.

Detailed explanation-3: -During the embryonic stage, the heart begins to beat and organs form and begin to function. At 22 days after conception, the neural tube forms along the back of the embryo, developing into the spinal cord and brain.