Final answer:
Once the fertilized egg starts dividing, it is called a zygote. The zygote undergoes mitotic cell divisions and becomes a blastocyst, which implants in the uterus.
Step-by-step explanation:
Once the egg is fertilized and begins to divide, it is called a zygote. After fertilization, the zygote undergoes several mitotic cell divisions, resulting in a ball of cells called a blastocyst. The blastocyst then implants itself in the lining of the uterus to continue its development.