What is Ploidy?
[[File:Haploid vs diploid.svg|thumb|120px|Diploid cells have two [[Homologous chromosome|homologous]] copies of each [[chromosome]].]] '''Ploidy''' is a term from [[genetics]] and [[cell biology]]. It is used to indicate the number of [[chromosome]] sets in a cell. Most [[eukaryote]]s have either one set (called [[haploid]]) or two sets (called '''diploid'''). Some other organisms are [[polyploid]], they have more than two sets of chromosomes. Some [[amphibian]]s are '''triploid''', with three sets. The [[endosperm]] cells in the seeds of many plants are also triploid. Some kinds of [[trout]] or [[salmon]] have four sets (''tetraploid''). Other examples: *[[wheat]]: 6 sets (''hectaploid'') *certain [[sturgeon]]s: 8 sets (''octoploid'') *[[strawberry|strawberries]]: 8 sets (''octoploid'') *plumed cockscomb (a plant, ''[[Celosia]] argentea''): 12 sets (''dodecaploid'') *[[Bryophyte]]s: body has one set; sporophyte has two sets. Sex cells ([[gamete]]s) are almost always haploid. If the reproductive stage (adult) is polyploid, then the gametes will have half the ploidy number of chromosomes. There are some variations of ploidy which are not discussed here. Some plant species with certain types of polyploidy do not use sexual reproduction, but survive with asexual methods. == Polyploidy == '''Polyploidy''' occurs in [[cell]]s and organisms when there are more than two paired (homologous) sets of [[chromosome]]s. Most organisms are normally '''diploid''', meaning they have two sets of chromosomes — one set inherited from each parent. Polyploidy may occur due to abnormal [[cell division]]. It is most commonly found in plants, but it does sometimes happen in animals.<ref>Gregory T.R. & Mable, B.K. 2005. Polyploidy in animals. In ''The evolution of the genome''. ed T.R. Gregory. Elsevier, San Diego. 427–517.</ref> Some estimates suggest that 30-80% of living plant species are polyploid, and many lineages show evidence of ancient polyploidy (paleopolyploidy) in their [[genome]]s.<ref>{{cite journal |author=Cui L, W