| 41. | Most birds have retinas with four spectral types of cone cells that are believed to mediate tetrachromatic color vision.
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| 42. | Cone cells and rods are connected through intermediate cells in the retina to nerve fibres of the optic nerve.
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| 43. | One proposed explanation for pentachromacy is a retina containing five distinct types of cone cells with differing absorption spectra.
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| 44. | Very few people see no color at all, a condition called monochromasy, in which there are no cone cells.
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| 45. | In contrast, nightjars have a limited number of cone cells, either lacking or having only a few oil droplets.
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| 46. | In vertebrates with three types of cone cells, at low light intensities the rod cells may contribute to color vision.
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| 47. | Individuals with the congenital form of this condition show complete absence of cone cell activity via electroretinography at high light levels.
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| 48. | Central vision is relatively weak in the dark ( scotopic vision ) since cone cells lack sensitivity at low light levels.
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| 49. | Red light only slowly depletes the rhodopsin stores in the rods, and instead is viewed by the red sensitive cone cells.
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| 50. | Steinberg determined that the cone cells renew themselves daily by shedding used-up parts that are then absorbed by the pigmented layer.
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