What is fertilization?

• A. The formation of gametes in the reproductive organs.
• B. The fusion of male and female gametes to form a zygote.
• C. The division of a fertilized egg into multiple cells.
• D. The implantation of the blastocyst into the uterine wall.

Answer: (B)

Fertilization is the moment when a male gamete (sperm) fuses with a female gamete (egg) to form a zygote. This fusion restores the diploid chromosome number and starts the first cell of a new individual, which then begins embryonic development.

This isn’t about making gametes—that process is gametogenesis. It isn’t about dividing the fertilized egg into many cells—that happens later in a stage called cleavage. And it isn’t about attaching the embryo to the uterus—that step is implantation, which occurs after the zygote has formed and begun to develop.