cell division

Process by which a cell divides. Cells are the basic units of life and they carry out basic functions that are characteristic of living organisms, such as growth and reproduction. Both growth and reproduction usually involve cell division. In plants and animals reproduction can be either sexual reproduction or asexual reproduction. Both involve cell division. In sexual reproduction the cell division that is used is meiosis. In asexual reproduction it is mitosis. In both forms of cell division, the chemical carrying inherited information, DNA, has to be copied before division. Rarely, mistakes occur causing mutations, but it is normally done accurately. Copying the DNA results in the duplication of structures called chromosomes in the nucleus. In cell division, the duplicated chromosomes are separated from each other into daughter cells.

In sexual reproduction male and female gametes combine. Gametes are produced by meiosis cell division. Usually the male and female gametes are produced by two different individuals. If so, sexual reproduction combines inherited information from the two parents. Most animals and plants reproduce sexually, though many plants also reproduce asexually.

The male and female sex organs of a plant are usually found in the flower. Many flowers contain both male and female organs. The male gametes of a plant are inside the pollen grains, and the female gametes are inside the ovules.

In mammals, the male gametes are called sperm and are made in the testes. The female gametes are eggs (see ovum) and are made in the ovaries.