Final answer:
The development of primary oocytes to a fertilized egg occurs through mitosis and two stages of meiosis, ending with fertilization by a sperm and formation of a diploid zygote that implants as a blastocyst in the uterus. The correct option is b.
Step-by-step explanation:
Development of Primary Oocytes to a Fertilized Egg
The development from primary oocytes to a fertilized egg involves a multistage process of cell division and differentiation.
Oogenesis starts with the division of oogonia through mitosis to form primary oocytes, which then undergo the first meiotic division to create secondary oocytes with a haploid number of chromosomes.
A secondary oocyte will complete meiosis II to form a haploid ovum only upon fertilization by a sperm. This crucial step also produces a second polar body, which typically degrades.
Upon fertilization, the secondary oocyte rapidly completes meiosis II, resulting in the formation of a diploid zygote and another polar body.
The zygote undergoes mitosis during its passage through the fallopian tube and arrives at the uterus as a multicellular blastocyst, which will then implant into the uterine wall, marking the beginning of gestation.
The fertilization process concludes with the fusion of the male and female pronuclei within the ovum, mixing the genetic material to form a single-celled diploid zygote, prepared with all necessary genetic instructions to develop into a human. The correct option is b.