A gamete ( ), reproductive cell, or sex cell, is a haploid cell that fuses with another haploid cell during fertilization in organisms that reproduce sexually. The name gamete was introduced by the German cytologist Eduard Strasburger in 1878.
The type of gamete an organism produces determines its sex and sets the basis for the sexual roles and sexual selection. Female gametes are called ova or egg cells, and male gametes are called sperm. There are almost invariably only two gamete types, all analyses showing that intermediate gamete sizes are eliminated due to selection. Since intermediate sized gametes do not have the same advantages as small or large ones, they do worse than small ones in mobility and numbers, and worse than large ones in supply.
Differences between gametes and somatic cells
In contrast to a gamete, which has only one set of chromosomes, a diploid somatic cell has two sets of homologous chromosomes, one of which is a copy of the chromosome set from the sperm and one a copy of the chromosome set from the egg cell. Recombination of the genes during meiosis ensures that the chromosomes of gametes are not exact duplicates of either of the sets of chromosomes carried in the parental diploid chromosomes but a mixture of the two.
thumb|263x263px|A human spermatozoon fusing with a human ovum. The spermatozoon is approximately 100,000 times smaller in size than the human ovum.
Artificial gametes
Artificial gametes, also known as in vitro derived gametes (IVD), stem cell-derived gametes (SCDGs), and in vitro generated gametes (IVG), are gametes derived from stem cells. The use of such artificial gametes would "necessarily require IVF techniques". Women who have passed menopause may be able to produce eggs and bear genetically related children with artificial gametes. This technique could be used to create cell lines for medical applications and for studying the heredity of genetic disorders. Plant sperm cells are their only motile cells, often described as flagellate, but more correctly as ciliate.
Bryophytes have 2 flagella, horsetails have up to 200 and the mature spermatozoa of the cycad Zamia pumila has up to 50,000 flagella. Cycads and Ginkgo biloba are the only gymnosperms with motile sperm.