Adults produce gametes through a type of cellular reproduction called mitosis. The process of a sperm cell and an egg cell fusing together is called fertilizationand produces a zygote. As a zygote undergoes rapid cell division to develop into an embryo, fetus, and eventually baby, the type of cellular reproduction being used is . As a baby grows into an adult, the type of cellular reproduction used is mitosis.

Mitosis.

Explanation:

Mitosis is the type of cellular reproduction which is used in order to develop an embryo, fetus, and eventually baby. In mitosis type of cell division, the parent and mature cells divides into two daughter cell. This type of cell division occurs in somatic or body cells whereas meiosis type of cell division occurs in the sex cells which produces four daughter cells from a single parent cell.