Purposes of reduction division - gametogesis & exceptions such as mosses & ferns
Diploid and haploid cells
All the cells in the body of an organism contain the same number of chromosomes. These are called somatic cells, or body cells, which include all body cells except sex cells. Somatic cells contain two sets of chromosomes. One set is inherited from the individual's mother and the other set is inherited from the individual's father. This is why we have charactristics of both our parents. Cells that have two sets of chromosomes in each cell are called diploid cells. The chromosomes in diploid cells are found in pairs. The pairs of chromosomes are called homologous pairs. One chromosomes from each homologous pair is inherited from an individual's mother and the other from the father.
During the first meiotic division, the number of chromosomes is reduced from the two sets of chromosomes in the parent cell to one set in the daughter cells. Cells with only one set of chromosomes in each cell are called haploid cells. During meiosis parent diploid cells divide to form haploid daughter cells.
Production of gametes- gametogenesis
The body cells used in sexual reproduction in most orgnisms are haploid cells. These cells are the sex cells or gametes. Sperm cells and egg cells or ova are gametes. In sexual reproduction , the chromosomes from the sperm and egg combine so that the new individual has two sets of chromosomes in each of its cells.
The gametes are formed by meiosis. The process of gamete formation is called gametogenesis. The new cells produced are not identical to the parent cell as they are in mitosis. Remember that mitosis occurs in somatic cells. Mitosis produces daughter cells that are identical to the parent cell, with the same number of chromosomes and the same characteristics.