Final answer:
The statement that the onset of sexual maturity marks the beginning of adolescence is true. Adolescence involves not only the physical maturation seen in puberty, with the development of primary and secondary sexual characteristics, but also cognitive, psychosocial, and emotional development.
Step-by-step explanation:
The onset of sexual maturity that marks the beginning of adolescence is true. Adolescence is a significant developmental period where an individual transitions from childhood to adulthood, encompassing not only the physical changes of puberty but also including cognitive, psychosocial, and emotional maturation.
Physical Changes During Puberty
During puberty, both primary and secondary sexual characteristics develop. Primary sexual characteristics are those directly involved in reproduction, such as the testes in males and the uterus and ovaries in females. Secondary sexual characteristics are traits not directly related to reproduction, like the development of facial hair in males, and breast development in females. The adrenal glands (adrenarche) and sex glands (gonadarche) also mature during this time, contributing to these changes.
Adolescent Growth Spurt
Another notable aspect of puberty is the Adolescent Growth Spurt (AGS), a period of rapid growth in height and weight. Girls typically start the growth spurt earlier than boys and will generally finish their physical growth before males. The AGS leads to sexual dimorphism in adult body size, composition, and shape.
Cognitive and Psychosocial Changes
Adolescence is not solely defined by physical changes. Significant cognitive development, such as improved abstract reasoning and impulse control, occurs during this time. There are also important psychosocial changes, like the formation of more mature relationships with peers and the development of a stronger sense of self.