1. What are the three stages of prenatal development and what are the main events that occur in each stage? Answer: The three stages of prenatal development are the germinal stage, the embryonic stage, and the fetal stage. The germinal stage lasts from conception to implantation (about two weeks) and involves the formation of the zygote, the cell division, and the attachment to the uterine wall. The embryonic stage lasts from implantation to the end of the eighth week and involves the differentiation of the cells into the three germ layers (ectoderm, mesoderm, and endoderm), the formation of the major organs and systems, and the development of the placenta and umbilical cord. The fetal stage lasts from the ninth week until birth and involves the growth and maturation of the organs and systems, the development of reflexes and sensory abilities, and the acquisition of body fat and hair. 2. What are some of the factors that influence physical growth and development in childhood and adolescence? Answer: Some of the factors that influence physical growth and development in childhood and adolescence are genetics, nutrition, health, hormones, environmental conditions, and physical activity. Genetics determine the potential height, weight, and body shape of an individual, as well as the timing of puberty. Nutrition affects the availability of energy and nutrients for growth and development, as well as the prevention or occurrence of diseases or deficiencies. Health influences growth and development by affecting the immune system, the susceptibility to infections or injuries, and the recovery from illnesses or wounds. Hormones regulate growth and development by stimulating or inhibiting cell division, differentiation, or metabolism. Environmental conditions affect growth and development by exposing individuals to various stimuli or stressors that can enhance or impair their physical well-being. Physical activity affects growth and development by stimulating muscle strength, bone density, cardiovascular fitness, coordination, and motor skills. 3. What are some of the major cognitive changes that occur in childhood and adolescence?