> (1) Are there gender differences in the numbers of rods and cones in the > retina?
For interesting coverage of the evolution of color vision in primates, see this Scientific American article from April 2009: http://www.scientificamerican.com/article.cfm?id=evolution-of-primate-color-vision The short version is that vision for blue is carried on chromosome 7 and vision for red and green is carried on X. This is the pattern seen in Old World primates (gibbons, chimps, gorillas, humans). Interestingly, only about 1/3 of New World primates (marmosets, tamarins, squirrel monkeys) -- females only -- have trichromatic vision. New World primates have 3 alleles in the gene pool: red, green, and one in between. If one X gets one and the other X gets a different one, then the primate has trichromatic vision. In Old World primates it appears that a recombination error put red and green together instead of one or the other, thus one X chromosome carries both red and green instead of one or the other. If you get the article from Academic Search Complete, you get this side note which Michael Smith alluded to: "Some women have four types of visual pigments instead of three. The fourth pigment resulted from a mutation in one of the longer-wavelength X-linked pigment genes and is known to shift the spectral sensitivity of the retina. Whether this shift actually creates the ability to perceive a broader range of hues is under active investigation. Thus far color vision testing has not produced consistent evidence for tetrachromatic vision, and humans who have this ability--if they exist--would not necessarily be aware of their visual anomaly." -- Sue Frantz Highline Community College Psychology, Coordinator Des Moines, WA 206.878.3710 x3404 sfra...@highline.edu Office of Teaching Resources in Psychology, Associate Director Project Syllabus APA Division 2: Society for the Teaching of Psychology APA's p...@cc Committee --- To make changes to your subscription contact: Bill Southerly (bsouthe...@frostburg.edu)
