Final answer:
The onset of gonadal functioning is best represented by puberty. During this stage, there is an increase in sensitivity of the gonads to hormone stimulation, leading to reproductive maturation and the development of secondary sex characteristics.
Step-by-step explanation:
The term that best means the onset of gonadal functioning is puberty. During puberty, there is a decrease in sensitivity to negative feedback in the hypothalamus and pituitary gland, and an increase in sensitivity of the gonads to FSH and LH stimulation. This leads to the initiation of spermatogenesis in boys and ovulation and menstruation in girls, as well as the development of secondary sex characteristics.