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Speciation via polyploidy: A diploid cell undergoes failed meiosis, producing diploid gametes, which self-fertilize to produce a tetraploid zygote. Polyploidy is frequent in plants, some estimates suggesting that 30–80% of living plant species are polyploid, and many lineages show evidence of ancient polyploidy (paleopolyploidy) in their genomes.
Polyploidy is important to wheat classification for three reasons: Wheats within one ploidy level will be more closely related to each other. Ploidy level influences some plant characteristics. For example, higher levels of ploidy tend to be linked to larger cell size. Polyploidy brings new genomes into a species.
The extreme in polyploidy occurs in the fern genus Ophioglossum, the adder's-tongues, in which polyploidy results in chromosome counts in the hundreds, or, in at least one case, well over one thousand. [citation needed] It is possible for polyploid organisms to revert to lower ploidy by haploidisation. [citation needed]
Wheat origins by repeated hybridization and polyploidy. [59] Not all species are shown. Some wheat species are diploid, with two sets of chromosomes, but many are stable polyploids, with four sets of chromosomes or six . [59] Einkorn wheat (Triticum monococcum) is diploid (AA, two complements of seven chromosomes, 2n=14). [60]
Classification systems serve the purpose of grouping organisms by characteristics common to each group. Plants are distinguished from animals by various traits: they have cell walls made of cellulose, polyploidy, and they exhibit sedentary growth.
Speciation via polyploidy: A diploid cell undergoes failed meiosis, producing diploid gametes, which self-fertilize to produce a tetraploid zygote.. Polyploidy is pervasive in plants and some estimates suggest that 30–80% of living plant species are polyploid, and many lineages show evidence of ancient polyploidy (paleopolyploidy) in their genomes.
Polyploidy and speciation in the genus Crepis was the subject of Stebbins' and Babcock's work on plant species formation. C. sibirica , shown here, was a species he examined. In 1935, Stebbins was offered a genetics research position at the University of California, Berkeley working with geneticist E. B. Babcock .
Having multiple sets of chromosomes is called polyploidy. Polyploidy is usually fatal in animals where extra chromosome sets upset fetal development, but is often found in plants. [17] A form of hybrid speciation that is relatively common in plants occurs when an infertile hybrid becomes fertile after doubling of the chromosome number.