Two reasons for cells to divide are repair of tissues and the growth and development of an organism. Cell division is necessary for any organism to grow and, once it has fully developed, to maintain healthy tissues.
There are two types of cell division, meiosis and mitosis. Meiosis occurs in sexually reproducing organisms like animals and plants. The process of meiosis involves DNA being replicated and divided into daughter cells that have half the number of chromosomes of the parent cell. This is to allow for two reproductive cells to join, thus creating new life. Mitosis occurs in a fully formed organism to replace old cells or repair damaged tissue. The process of mitosis results in the replication of identical cells.