Final answer:
A secondary oocyte completes meiosis II after fertilization by a sperm in the Fallopian tube, forming a diploid zygote. Without fertilization, the secondary oocyte disintegrates.
Step-by-step explanation:
The secondary oocyte undergoes meiotic division after it is fertilized by a sperm as it passes through the Fallopian tube. During this process, the cell quickly completes meiosis II, forming a diploid zygote and another polar body, which typically disintegrates. If fertilization does not occur, the secondary oocyte does not complete meiosis II and eventually disintegrates.
At the initiation of ovulation, the transition from primary to secondary oocyte is triggered by a surge of luteinizing hormone. The secondary oocyte, containing most of the cellular material and organelles, is then released during ovulation and begins its travel toward the uterus, being arrested at the metaphase II stage until fertilization.