Final answer:
Puberty generally begins around age 11-12 in boys and around age 9-10 in girls. During puberty, there are significant changes in body composition, growth, and development.
Step-by-step explanation:
In boys, puberty generally begins between the ages of 11 and 12, when the external genitals and pubic hair start to develop. In girls, puberty generally begins between the ages of nine and ten, when the breasts and pubic hair start to develop. The adolescent growth spurt (AGS) is a period of rapid growth in height and weight. It also includes significant changes in body composition and shape. Girls start the growth spurt earlier than boys and typically have a somewhat lower peak growth rate.
Sex differences in the AGS result in sexual dimorphism in adult size, body composition, and shape. Other body systems also undergo rapid growth and development during the AGS. Although the brain does not increase very much in size during adolescence, it does become more complex. The cerebral cortex becomes more folded, and unused pathways are eliminated. The most significant changes occur in the prefrontal cortex, which controls executive functions, such as decision making, abstract reasoning, and impulse control.