Final answer:
The number of eggs and follicles reduces significantly by the age of menopause due to a natural process known as atresia. Fertility declines gradually from a woman's twenties and more rapidly after age 35 until menopause occurs, usually between the mid-40s and mid-50s.
Step-by-step explanation:
Many eggs and follicles undergo atresia during childhood, so their number is greatly reduced by the age of menopause. The death of ovarian follicles, or atresia, occurs throughout a female's life, and by menopause, there are no follicles remaining. During the aging process, especially as women approach their mid-40s to mid-50s, ovarian sensitivity to follicle-stimulating hormone (FSH) and luteinizing hormone (LH) decreases. This hormonal change leads to fewer menstrual cycles and eventually menopause, signaling the end of fertility. Moreover, female fertility peaks in the twenties and gradually declines until more rapid decreases after the age of 35, culminating in menopause.