fertilization
Organisms that reproduce sexually by joining gametes , a process known as fertilization , must have a mechanism to produce haploid gametes. This mechanism is meiosis , a type of cell division that halves the number of chromosomes. Meiosis occurs only in gamete producing cells within the gonads. During meiosis the pairs of chromosomes separate and segregate randomly to produce gametes with one chromosome from each pair. Meiosis involves two nuclear and cell divisions without an interphase in between, starting with one diploid cell and generating four haploid cells Figure below . Each division, named meiosis I and meiosis II, has four stages: prophase, metaphase, anaphase, and telophase. These stages are similar to those of mitosis, but there are distinct and important differences.