Diplonts are organisms whose cell nuclei, with the exception of gametes (germ cells), contain a double ( diploid ) set of chromosomes . The gametes, on the other hand, have a simple ( haploid ) set of chromosomes. Opposite the Diplonts are the Haplonts , in which all cells except for the diploid zygote are haploid. Thirdly, there are the diplohaplons , in which diploid and haploid generations alternate.
Sexually reproducing organisms go through a core phase change , in which there is an alternation between a haploid and a diploid phase (special cases with polyploidy not considered here). The transition from the diploid to the haploid phase occurs during the reduction division ( meiosis ), in which the chromosomes are divided up so that each haploid daughter cell receives a homologous partner of a chromosome pair. These haploid cells are the gametes: in the female sex the egg cell , in the male the sperm . During fertilization, they fuse in pairs to form a diploid zygote , from which the new diploid organism develops.
Almost all multicellular animals (Metazoa) are Diplonts (with the exception of the species with haplodiploid sex determination ). In contrast, all more highly organized plants ( seed plants , ferns and mosses ) are diplohaplons. In the seed plants, the haploid generation is greatly reduced and represented by the few-celled pollen grain and by the embryo sac in the ovule .
The terms Diplont and Haplont were incorporated into biological terminology by the zoologist Max Hartmann in 1918 (in his work Theoretical Meaning and Terminology of Hereditary Phenomena in Haploid Organisms (Chlamydomonas, Phycomyces, Honeybee) ). The term on which it is based, diploidy, dates back to 1905 (in typical and allotypic core division. Results and discussions ) by the botanist Eduard Strasburger .
- ↑ Section Life History, in Georg Toepfer: Historical Dictionary of Biology. History and theory of basic biological concepts. Volume 2: Feeling - Organism. JB Metzler Verlag, Stuttgart and Weimar 2011. ISBN 978-3-476-02318-6 , on pp. 497-500.
- ^ Section Fertilization, in Georg Toepfer: Historical Dictionary of Biology. History and theory of basic biological concepts. Volume 1: Analogy - Wholeness. JB Metzler Verlag, Stuttgart and Weimar 2011. ISBN 978-3-476-02317-9 , on p. 169.
- Lexicon of biology : Diplonten . Spectrum, Heidelberg 1999.