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Information about Dichromat

Dichromacy in humans is a moderately severe color vision defect in which one of the three basic color mechanisms is absent or not functioning. It is hereditary and sex-linked, predominantly affecting males.[1] Dichromacy occurs when one of the cone pigments is missing and color is reduced to two dimensions.[2]

Organisms with dichromacy are called dichromats. Dichromats can match any color they see with a mixture of no more than two pure spectral lights. By comparison, a trichromat requires three pure spectral lights to match all colors in their visual spectrum.

There are various kinds of colour blindness. Protanopia is a severe form of red-green colour-blindness, where there is impairment in perception of very long wavelengths, such as reds. To these sufferers, reds are perceived as beige and greens tend to look like reds. Protanomaly is a less severe version. Deuteranopia consists of an impairment in perceiving medium wavelengths, such as greens. Deuteranomaly is a less severe form of deuteranopia. Those living with deuteranomaly cannot see reds and greens like normal people, however they can still distinguish them in most cases. A more rare form of colour blindness is tritanopia, where there exists an inability to perceive short wavelengths, such as blues. Sufferers have trouble distinguishing between yellow and blue and tend to mistake greens for blues and yellows for reds.

Dichromacy in mammals

It is currently believed that most mammals are dichromats. The straightforward exceptions are primates closely related to humans, which are usually trichromats, and sea mammals (both pinnipeds and cetaceans) which are monochromats. New World monkeys are a partial exception: in most species, males are dichromats, and about 60% of females are trichromats, but the owl monkeys are monochromats, and both sexes of howler monkeys are trichromats. Recent research (e.g. Arrese et al, 2005) suggests that trichromacy may be widespread among marsupials.

Notes

1. ^ Cassin, B. and Solomon, S. Dictionary of Eye Terminology. Gainsville, Florida: Triad Publishing Company, 1990.
2. ^ "Guidelines: Color Blindness." Tiresias.org. Accessed September 29, 2006.

References

  • Arrese, C. A., Oddy, A. Y., Runham, P. B., Hart, N. S., Shand, J., Hunt, D. M., * Beazley, L. D. (2005). Cone topography and spectral sensitivity in two potentially trichromatic marsupials, the quokka (Setonix brachyurus) and quenda (Isoodon obesulus). Proceedings of the Royal Society of London Series B, 272, 791-796.
  • Jacobs, G. H., & Deegan, J. F. (2001). Photopigments and colour vision in New World monkeys from the family Atelidae. Proceedings of the Royal Society of London, Series B, 268, 695-702.
  • Jacobs, G. H., Deegan, J. F., Neitz, J., Crognale, M. A., & Neitz, (1993). Photopigments and colour vision in the nocturnal monkey, Aotus. Vision Research, 33, 1773-1783.
  • Mollon, J. D., Bowmaker, J. K., & Jacobs, G. H. (1984). Variations of colour vision in a New World primate can be explained by polymorphism of retinal photopigments. Proceedings of the Royal Society of London, Series B, 222, 373-399.
  • Sternberg, Robert J. (2006): Cognitive Psychology. 4th Ed. Thomson Wadsworth.

External links

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Color vision
spectrum (plural spectra) is a condition that is not limited to a specific set of values but can vary infinitely within a continuum. The word saw its first scientific use within the field of optics to describe the rainbow of colors in visible light when separated using a
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Trichromacy is the condition of possessing three independent channels for conveying colour information, derived from the three different cone types.[1] Organisms with trichromacy are called trichromats.
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visible spectrum (or sometimes optical spectrum) is the portion of the electromagnetic spectrum that is visible to (can be detected by) the human eye. Electromagnetic radiation in this range of wavelengths is called visible light or simply light.
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Color blindness, or color vision deficiency, in humans is the inability to perceive differences between some or all colors that other people can distinguish. It is most often of genetic nature, but may also occur because of eye, nerve, or brain damage, or due to exposure to certain
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Color blindness, or color vision deficiency, in humans is the inability to perceive differences between some or all colors that other people can distinguish. It is most often of genetic nature, but may also occur because of eye, nerve, or brain damage, or due to exposure to certain
..... Click the link for more information.
Color blindness, or color vision deficiency, in humans is the inability to perceive differences between some or all colors that other people can distinguish. It is most often of genetic nature, but may also occur because of eye, nerve, or brain damage, or due to exposure to certain
..... Click the link for more information.
Color blindness, or color vision deficiency, in humans is the inability to perceive differences between some or all colors that other people can distinguish. It is most often of genetic nature, but may also occur because of eye, nerve, or brain damage, or due to exposure to certain
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Mammalia
Linnaeus, 1758

Subclasses & Infraclasses
  • Subclass †Allotheria*
  • Subclass Prototheria
  • Subclass Theria

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Catarrhini
É. Geoffroy, 1812

Families

Cercopithecidae
Hylobatidae
Hominidae

Catarrhini is a parvorder of the Primates, one of the three major divisions of the suborder Haplorrhini.
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Pinnipeds ("fin-feet", lit. "winged feet") are marine mammals belonging to the former biological suborder Pinnipedia (sometimes now a superfamily) of the order Carnivora. The pinnipeds now fall within the suborder Caniformia and comprise the families Odobenidae (walruses),
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Cetacea
Brisson, 1762

Diversity
Around 88 species; see list of cetaceans or below.

Suborders

Mysticeti
Odontoceti
Archaeoceti (extinct)
(see text for families)

The order Cetacea
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Monochromacy, also known as "total color blindness"[1], is the lack of ability to distinguish colors; caused by cone defect or absence.[2] Monochromacy occurs when two or all three of the cone pigments are missing and color and lightness vision is reduced to
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Platyrrhini
E. Geoffroy, 1812

Families

Cebidae
Aotidae
Pitheciidae
Atelidae

The New World monkeys are the four families of primates that are found in Central and South America: Cebidae, Aotidae, Pitheciidae and Atelidae.
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Aotidae
Poche, 1908 (1865)

Genus: Aotus
Illiger, 1811

Type species
Simia trivirgata
Humboldt, 1811

Species

Aotus lemurinus
Aotus hershkovitzi

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Alouattinae
Trouessart, 1897 (1825)

Genus: Alouatta
Lacepede, 1799

Type species
Simia belzebul
Linnaeus, 1766

Species

Alouatta coibensis
Alouatta palliata

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Marsupialia
Illiger, 1811

Orders
  • Didelphimorphia
  • Paucituberculata
  • Microbiotheria
  • Dasyuromorphia
  • Peramelemorphia
  • Notoryctemorphia
  • Diprotodontia
  • Sparassodonta (extinct)
  • Yalkaparidontia (extinct)
Marsupials
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Cal Henderson (born Callum James Henderson-Begg on January 17 1981) is a British computer programmer and author based in San Francisco.

He's best known for co-owning and developing the online creative community B3ta[1]
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Color vision is the capacity of an organism or machine to distinguish objects based on the wavelengths (or frequencies) of the light they reflect or emit. The nervous system derives color by comparing the responses to light from the several types of cone photoreceptors in the eye.
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Color blindness, or color vision deficiency, in humans is the inability to perceive differences between some or all colors that other people can distinguish. It is most often of genetic nature, but may also occur because of eye, nerve, or brain damage, or due to exposure to certain
..... Click the link for more information.
opponent process is a color theory that states that the human visual system interprets information about color by processing signals from cones and rods in an antagonistic manner.
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Monochromacy, also known as "total color blindness"[1], is the lack of ability to distinguish colors; caused by cone defect or absence.[2] Monochromacy occurs when two or all three of the cone pigments are missing and color and lightness vision is reduced to
..... Click the link for more information.
Trichromacy is the condition of possessing three independent channels for conveying colour information, derived from the three different cone types.[1] Organisms with trichromacy are called trichromats.
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Tetrachromacy is the condition of possessing four independent channels for conveying color information, or possessing four different cones, one other than RGB. Organisms with tetrachromacy are called tetrachromats.
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Pentachromacy is the condition of possessing five independent channels for conveying color information. Organisms with pentachromacy are called pentachromats. For these organisms, the perceptual effect of any arbitrarily chosen light from its visible spectrum can be matched by a
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