The human reproductive system and life cycle are described in 3 stages. During puberty, the body experiences physical and psychological changes as girls begin menstruating and boys start producing sperm cells. The human life cycle involves 4 stages - infancy where rapid growth occurs, childhood where skills develop, adolescence/puberty where reproductive maturity is reached, and adulthood where the reproductive cycle is complete. The document also discusses taking care of the human reproductive organs but provides no additional details.