Final answer:
At puberty, a female has many primordial follicles in her ovaries, which can develop into primary and then secondary follicles through a process called folliculogenesis. This process also involves the maturation of a follicle and the completion of meiosis I by the primary oocyte within the follicle.
Step-by-step explanation:
At the onset of puberty, a female typically has a substantial number of primordial follicles within her ovaries. These follicles are in a resting state, with each comprising an oocyte surrounded by a single layer of granulosa cells. During folliculogenesis, a few primordial follicles are activated each day to join a growing pool of immature follicles called primary follicles. As they develop, these follicles transition into secondary follicles with a primary oocyte and multiple layers of granulosa cells. The primary oocyte within these follicles completes meiosis I to form a secondary oocyte and a first polar body during the maturation of a follicle.
It's important to note that throughout a female's lifetime, from birth where she has one to two million oocytes, the number of available follicles decreases through a process called atresia, until menopause when no follicles remain. The growth and development of ovarian follicles is a crucial part of the reproductive system as it leads to ovulation, typically occurring once every 28 days.