Cells reproduce themselves through division, and the type of division depends on the cell's role. Mitosis is the process by which a single cell divides to produce two genetically identical diploid daughter cells. It supports growth, tissue repair, and asexual reproduction in organisms. Mitosis proceeds through four recognizable stages: prophase, when chromosomes condense and become visible; metaphase, when chromosomes align at the cell's equator; anaphase, when sister chromatids pull apart toward opposite poles; and telophase, when two new nuclei reform. Cytokinesis, the physical splitting of the cytoplasm, usually follows and completes the process.
Meiosis is a specialized form of cell division that produces gametes, namely sperm and egg cells, for sexual reproduction. Unlike mitosis, meiosis consists of two successive divisions and results in four non-identical haploid cells, each containing half the original chromosome number. This reduction in chromosome number is essential because fertilization then restores the diploid number in the offspring. Meiosis also introduces genetic diversity through two key mechanisms: crossing over, in which homologous chromosomes exchange segments during the first division, and independent assortment, in which different chromosome pairs line up randomly.
The differences between mitosis and meiosis reflect their different purposes. Mitosis preserves the chromosome number and produces clones for growth and maintenance, while meiosis reduces the chromosome number by half and shuffles the genetic deck to create variation. This variation is the raw material upon which evolution acts, making meiosis a critical bridge between generations and a key driver of biological diversity.