What is fertilization?

Fertilization is the process by which a sperm cell successfully unites with an egg cell, resulting in the creation of a zygote. This is the critical first step in sexual reproduction, as it combines the genetic material from both the male and female gametes, leading to the formation of a new organism. The significance of fertilization lies in its role of initiating the development of an embryo, which then begins to undergo a series of divisions and growth processes.

The other choices reflect important biological processes but do not accurately define fertilization. For example, the development of an embryo refers to the stages that occur after fertilization, while cell division relates to the process of a single cell splitting into two or more cells, not the joining of sperm and egg. Implantation, on the other hand, refers to the process of the zygote embedding itself into the uterine lining after fertilization has already occurred. Therefore, the correct definition of fertilization centers around the initial meeting and fusion of sperm and egg.