Final answer:
The second meiotic division in oogenesis occurs after a secondary oocyte is fertilized by sperm, leading to the formation of a haploid ovum and a second polar body.
Step-by-step explanation:
The second meiotic division in oogenesis occurs after fertilization. A primary oocyte begins the process of meiosis before birth and gets arrested at prophase I. During a female's reproductive years, usually around ovulation, the cell completes the first meiotic division to form a secondary oocyte and a small polar body. The unequal division ensures that most cytoplasmic contents are retained in the secondary oocyte, which is necessary for the development of a fertilized egg. The second meiotic division resumes only if the secondary oocyte is fertilized by a sperm, resulting in the formation of a haploid ovum (egg) and another polar body. This process is essential for producing an egg ready for embryonic development, containing a complete set of chromosomes - half from the sperm and half from the oocyte.