Genome Duplications | Convergent evolution

A whole genome duplication is exactly what it sounds like: an event which creates an organism with additional copies of the entire genome of a species. Regular cells of most organisms that reproduce sexually contain two copies of their entire genome (one inherited from each parent), a state known at being diploid. A whole genome duplication might result from an organism that inherited two copies of its genome from each parent (four copies total). A doubling from two to four copies of the genome is known as a tetraploidy. A general rule of thumb is that organisms with even ploidy numbers (2,4,6,8) can often successfully reproduce, but organisms with odd ploidy numbers(3,5, etc) will be unable to. Convergent evolution refers to the evolution in different lineages of structures that are similar or ‘analogous’, but that cannot be attributed to the existence of a common ancestor; in other words, the fact that the structures are analogous does not reflect homology. A similarity may reside at the phenotypic level, in which case the lineages share the overt trait, but the underlying DNA sequences are different. Convergent evolution occurs when species occupy similar ecological niches and adapt in similar ways in response to similar selective pressures. Traits that arise through convergent evolution are referred to as ‘analogous structures’. They are contrasted with ‘homologous structures’, which have a common origin. The opposite of convergent evolution is ‘divergent evolution’, whereby related species evolve different traits. Well-documented cases of convergent evolution of similar DNA sequences are not plentiful; such cases are usually restricted to a few amino acids. Convergent evolution can mislead phylogenetic inference because it mimics shared ancestry. Standard phylogenetic methods are not equipped to differentiate between the two. When convergent evolution is mistaken for homology, this produces a phylogenetic tree that is falsely reticulate or bushy in appearance, that is, species appear to originate from a common ancestor when in fact that is not the case. #outgroups #ingroup #Homology #Homoplasy #cladogram #Phylogram #domain #kingdom #phylum #Class #genus #ScientificNames #taxonomicHierarchy #species #phyliogeneticTree #Evolution #speciation #diagram #branchingInAPhylogeneticTree #Genetics #bilology #taxonomy #populationGenetics #hawaiiIslands #founderEffect #geneticDrift #geneticVariation #taxa #clade #Paraphyletic #Monophyletic #Polyphyletic #taxonomicRank #HumanGenomeProject #genomeSequencing