The number of primary oocytes in the ovaries declines from one to two million in infancy to approximately how many by puberty?

1. Oogonia form primary oocytes before birth, and this pool only ever declines from that point forward. 2. An infant's ovaries contain one to two million primary oocytes. 3. By the time of puberty, most of this original stock has already been lost through atresia. 4. 4,000 and 40,000 are both different figures a reader might guess from memory, but neither matches the specific figure given here. 5. 4,000,000 is also incorrect for the same reason: it does not match the specific figure given here. 6. The remaining number at puberty as approximately 400,000. _Source: OpenStax Anatomy and Physiology (CC BY 4.0), Ch 27 "The Reproductive System", p.1294 §Oogenesis_