Development of an organism from the zygote to the full grown stage takes place by the division of cells. Even after full size has been attained, replacement of cells takes place by cell division. The process of cell division whereby the chromosomes are duplicated and distributed equally to the daughter cells is called mitosis.
Fertilization and meiosis are compensating events. In sexually reproducing organisms male and female gametes fuse together to form the zygote. If the gametes had the same number of chromosomes as the somatic cells, then the zygote would have twice the diploid number of chromosomes. This number would go on doubling with each generation.
Mitosis and meiosis are two types of processes of nuclear division within the process of division of cells of living organisms. Most one celled organisms and most of the cells of multi-cell organisms divide by mitosis. In this process the nucleus divides to form two identical nuclei. Once this happens the next phase of cell division involving division of cytoplasm takes place producing two daughter cells.
Meiosis is the process applicable in sexual reproduction. In this process it is necessary for a male cell called sperm to first unite with a female cell called egg. In this process two separate nucleus division of sex cells takes place. Each chromosomes in the nucleus is duplicated before the first division producing two joined chromatids. each pair of chromatids then lines up side by side with other chromosome of its pair. The paired chromosomes then separate. Then cytoplasm divides in two, each receiving one pair of chromosomes consisting of two chromatids, forming two daughter cells. Each of these daughter cells again divides, with each daughter cell receiving one chromatid from each pair of chromosome. In this way on sex cell divides in four sex cells.
Cell division occurs through mitosis and meiosis.
Mitosis occurs in cells that are autosomal cells. It is also known as asexual reproduction. The cell reproduces itself. Mitosis commonly occurs in organisms such as bacteria, hydra, and single celled organisms.
Meiosis requires two cells, a male and a female, called a "gamete" or "sex cells." Each cell must divide twice and passes on hereditary information in order to produce off spring with similar features. Plants, animals, and insects reproduce in this manner.
Nature has adapted to allow for the reproduction of life. In order for an organism to repopulate it must have a means of creating duplicate and specific cell replication. Both processes are necessary for life to continue.