The female sex cell, also known as an egg cell or ovum, produces a zygote when it is fertilized by a male sperm cell.

Here's the breakdown:

* Egg cell: Contains half of the genetic material needed for a new individual.

* Sperm cell: Contains the other half of the genetic material.

* Fertilization: When a sperm cell successfully enters and fuses with an egg cell.

* Zygote: The single cell that results from fertilization, containing a full set of genetic material from both parents.

The zygote then undergoes rapid cell division and development, eventually forming a complete embryo and ultimately a new individual.