Editing Color vision (section)

==Dimensionality==
Color vision is categorized foremost according to the dimensionality of the color [[gamut]], which is defined by the number of [[primary color|primaries]] required to represent the color vision. This is generally equal to the number of [[photopsin]]s expressed: a correlation that holds for [[vertebrate]]s but not [[invertebrate]]s. The common vertebrate ancestor possessed four photopsins (expressed in [[cone cell|cones]]) plus [[rhodopsin]] (expressed in [[rod cell|rods]]), so was [[tetrachromatic]]. However, many vertebrate [[Lineage (evolution)|lineages]] have lost one or many photopsin genes, leading to lower-dimension color vision. The dimensions of color vision range from 1-dimensional and up:
{| class="wikitable nowrap"
!Dimension
!Characteristic
!Occurrence
|-
|[[Monochromacy]]
|1D color vision<br /> lack of any color perception
|Some [[mammals]], including [[Pinnipeds]], [[Cetaceans]] and [[Xenarthra]]<ref name="Peichl">{{cite journal|last1=Peichl|first1=Leo|last2=Behrmann |first2=Gunther |last3=Kroger |first3=Ronald H. H.|title=For whales and seals the ocean is not blue: a visual pigment loss in marine mammals|journal=European Journal of Neuroscience|date=April 2001|volume=13|issue=8|pages=1520–1528|doi=10.1046/j.0953-816x.2001.01533.x|pmid=11328346|citeseerx=10.1.1.486.616|s2cid=16062564}}</ref><ref>{{Cite journal|last1=Emerling|first1=Christopher A.|last2=Springer|first2=Mark S.|date=2015-02-07|title=Genomic evidence for rod monochromacy in sloths and armadillos suggests early subterranean history for Xenarthra|journal=Proceedings of the Royal Society B: Biological Sciences|volume=282|issue=1800|pages=20142192|doi=10.1098/rspb.2014.2192|issn=0962-8452|pmc=4298209|pmid=25540280}}</ref>
|-
| [[Dichromacy]]
|2D color vision
|Most mammals and a quarter of [[color blind]] [[humans]]
|-
|[[Trichromacy]]
|3D color vision
|Most [[Old World monkey]]s and [[ape]]s, including most humans; possibly [[monotreme]]s and some [[marsupial]]s
|-
|[[Tetrachromacy]]
|4D color vision 
|Most [[bird]]s, [[reptile]]s and [[teleost|fish]], and rarely in humans
|-
|[[Pentachromacy]] and higher
|5D+ color vision
|Rare in [[vertebrates]]
|}