meiosis
Sexual reproduction involves two parents. As you can see from Figure below , in sexual reproduction, parents produce reproductive cellscalled gametes that unite to form an offspring. Gametes are haploid cells. This means they contain only half the number of chromosomes found in other cells of the organism. Gametes are produced by a type of cell division called meiosis, which is described in detail below. The process in which two gametes unite is called fertilization . The fertilized cell that results is referred to as a zygote . A zygote is diploid cell, which means that it has twice the number of chromosomes as a gamete.