[Campbell Biology P.1083] After human fertilization, what is the correct sequence of early em... | Practice Question

After human fertilization, what is the correct sequence of early embryonic development and implantation according to the text?

  • A: Fertilization in the uterus -> cleavage to zygote -> blastocyst formation -> implantation in oviduct.
  • B: Fertilization in the oviduct -> zygote undergoes cleavage -> blastocyst forms in about 5 days -> implantation in endometrium.
  • C: Blastocyst implants immediately after fertilization -> zygote forms -> cleavage begins.
  • D: Sperm and egg fuse in the uterus -> blastocyst forms in 24 hours -> implantation occurs after 38 weeks of gestation.

Explanation

The text states: 'Fertilization—also called conception in humans—occurs when a sperm fuses with an egg mature oocyte in an oviduct Figure 46.15 . The zygote begins a series of cell divisions called cleavage about 24 hours after fertilization and after an additional 4 days produces a blastocyst, a sphere of cells surrounding a central cavity. A few days later, the embryo implants into the endometrium of the uterus.' This matches option B, noting that 'about 5 days' for blastocyst formation 24 hours + 4 days is accurate.