Dichromat

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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. Dichromacy occurs when one of the cone pigments is missing and color is reduced to two dimensions.

Organisms with dichromacy are called dichromats. Dichromats can match any color they see with a mixture of no more than two pure spectral lights

Spectrum

A spectrum 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 triangular prism ; it has since been applied by analogy to many fields other than op...
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Spectrum

Trichromat

Trichromacy or trichromaticism is the condition of possessing three independent channels for conveying color information, derived from the three different Cone cell types....
requires three pure spectral lights to match all colors in their visual spectrum.

Classification

There are various kinds of color blindness

Color blindness

Color blindness, a color vision deficiency, is the inability to perceive differences between some of the colors that others 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 chemicals....
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Protanopia is a severe form of red-green color-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 those without this condition, however they can still distinguish them in most cases.

A more rare form of color 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 mammal

Mammal

Mammals are a class of vertebrate animals whose name is derived from their distinctive feature, mammary glands, with which they feed their young....
s are dichromats. The straightforward exceptions are primates closely related to humans

Catarrhini

Catarrhini is a parvorder of the Primates, one of the three major divisions of the suborder Haplorrhini. It contains the Old World monkeys and the apes ....
, which are usually trichromats, and sea mammals (both pinniped

Pinniped

Pinnipeds or fin-footed mammals are a widely distributed and diverse group of semi-aquatic marine mammals comprising the families Odobenidae , Otariidae , and Phocidae ....
s and cetacea

Cetacea

The order Cetacea includes whales, dolphins, and porpoises. Cetus is Latin and is used in biological names to mean "whale"; its original meaning, "large sea animal", was more general....
ns) which are cone 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 cone monochromats, and both sexes of howler monkey

Howler monkey

Howler monkeys are among the largest of the New World monkeys. Nine species are currently recognised. Previously classified in the family Cebidae, they are now placed in the family Atelidae....
s are trichromats.

Recent research suggests that trichromacy may be widespread among marsupial

Marsupial

Marsupials are an infraclass of mammals, characterized by a distinctive Pouch , in which females carry their young through early infancy....
s.

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by Cal Henderson
Cal Henderson

Cal Henderson is a British computer programmer and author based in San Francisco. He was educated at Sharnbrook Upper School and Community College....
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