This document discusses developmental theories and the role of heredity. It describes Erikson's psychosocial developmental theory which consists of 8 stages that impact personality development. Each stage involves resolving a psychosocial problem. It also describes Freud's psychosexual developmental theory, which includes 5 stages focused on different parts of the body. The role of heredity is discussed, defined as the passing of physical traits from parents to offspring through genes and DNA. Heredity can influence both physical features and behaviors.