Why white skinned creatures living in dark environments?
551674
Short Answer: no need to develop pigments.  \n\nThe explanation: sunlight is harmful (ergo you use sunscreen) because of UV light, and pigments are produced by our skin cells to absorb the force brought on by UV rays, keeping your DNA from absorbing them.  If you're not exposed to sunlight, your skin doesn't need to produce and therefore doesn't produce much pigmentation, if any.  Same happens in animals.  If their permanent condition is as such, they eventually lose all ability to produce pigments simply because they can invest the energy on something that will give them the advantage to survive in their environment.  \n\nAs for blindness, you need light in order to see, and just like we can't see in total darkness, fish can't see in darkness either.  So, animals that live in absolutely dark environments don't need sight, and thus don't have it.  They'd rather spend the energy needed to develop sight (which is useless) in developing other sensory organs that will give them an advantage as hunter, to avoid being something else's lunch or both.\n\nMulti colouration in animals exists for many reasons, the two main ones are \n\n1- as disguise to fool prey (to eat) or to fool predators (to not be eaten)\n\n2- as an attractive feature for sexual selection, so that potential mates identify them clearly and select them for mating.  \n\nIn any case, competition to be the best hunter, the best hiding or the one that attracts more females or males drives selection and thus evolution.  \n\nRemember: if you get eaten, die of starvation or don't reproduce, you don't get to pass on your genes.  As such, any special traits you might have do not get passed on in the gene pool and those traits dissapear with your dead rotting self.  If more humans knew this, we'd be a little more appreciative of our uniqueness (read: selfish) and suicide rate would go way down.  \n\nThat's what evolution is all about, survive until you get laid and knock someone up or to get someone to knock you up.
267530
All penguins have a white underside and a dark (mostly black) upperside. This is for camouflage. A predator looking up from below (such as an orca or a leopard seal) has difficulty distinguishing between a white penguin belly and the reflective water surface. The dark plummage on their backs camouflages them from above.
503222
deep sea creatures because some are blind and some are glowy and some are spikey and some squishy.
1173819
Well, they have to be camouflaged for swimming in the sea.  Look at most deep - water fish (not the show - off types, that live around coral reefs), for example.  They tend to have dark colours on the side that faces up, while they swim, and pale on the other side.\n\nThis hides them from predators from above and below, better than other colour schemes.  From above, they seem dark, like the deep sea.  They must not shine, reflecting back sunlight more than deep water will.  From below, they are pale against the brighter background of the sunshine coming down through the water; they do not give as much of a shadow as if they were dark on their underside.\n\nOn land, especially in a snowy landscape, they do not seem camouflaged, but think of them as fish, and it makes more sense.\n\nBTW, Anthony, you have polar bears and seals, at the north pole / Arctic circle.  We have penguins and seals in the Southern Ocean, and Antarctica.  We have penguins in Australia too; they are a tourist attraction, where they are able to be viewed; they have become familiar with humans.
894876
So they can breath. Their lungs aren't nearly as efficient as ours so they still require to breath through their skin, this can only be done on moist surfaces (this is also why our lungs are moist).
783306
Planaria are very sensitive to light. They feed in darkness. If they stay in light too much it overloads their simple sensory system and they can't function very well.
689617
Animals that see at night have several adaptations; these can include some or all of the following:\n- Relatively larger eyes (example: owls)\n- High density of rods (light-detecting sensory cells). Rods have a pigment called rhodopsin that is especially sensitive to light even at low levels (in these animals, the concentration levels of rhodopsin are also higher).\n- Possession of a tapetum lucidum (this is Latin for "bright or clear carpet"). This is a highly reflectant layer that is situated behind the retina, it collects all the light including the faintest wavelengths and redirects it to the retina, enhancing vision.\n\nSee a diagram here:\nhttp://www.natureshift.org/rangerR/forest/images/eye-dia.jpg\n\nThis reflecting layer is what causes the eyes light up when they are illuminated by strong focused light. The color of the eye shine depends on the structure of the tapetum lucidum and also on the pigmentation of the animal. \nSee more about these structures in the following Q&A:\nhttp://answers.yahoo.com/question/;_ylt=AuiC1gBR8wcII9_SKbjYh4MjzKIX?qid=1006033114457\n\nThis high sensitivity to light is also reflected in the shape of the iris. Nocturnal animals often have vertical pupils that are able to narrow to mere slits during the day, to protect the extremely sensitive mechanism from the intense daylight.
498185
I think you mean anole lizards. They do change color, but they are definitely NOT chameleons.
799888
They are bright because they have pigment molecules in their petals that absorb particular wavelenghts of visible light, making them appear colored.\n\nBut the reason they evolved those pigments was to attract pollinators.
781893
These bacteria probably have the lux gene which codes for bioluminesence. A resonable mechanism that would cause this to arise is mutation. These lighted cells would probably have benefited some how from glowing in the dark. Some deep sea fishes have bacteria which code for this gene (Vibrio fischer) Which may have helped these fish find food in the dark waters. Thus those fishes without this gene would have died out because of natural selection. What you could do is put these fishes with the bacteria that glow in the dark in the same pool of dark water as the fishes without this gene. Then provide a limited food source so that not everyone could receive food and only the strongest would survive. If the fishes without this bacteria eventually died out but the others stayed alive, you have proven your hypothesis. If not, then failure willl be an obsticle to overcome.\n\nHope i was helpful
871649
That is a very interesting question.\nno . . . . but there is one exception\nIn a camera flash, the light is reaching through the pigmentation\nto the retina, the light-sensitive membrane covering the back wall of the eyeball, which is the color red.\nthe only organisms that have eyes visibly red are ones that are albino\nalbino organisms have less melon(color) in there skin, hair, and eyes.\nresulting in the clear vision to their retina, which causes their eyes to be the color red.\n(i.e. white mice that have red eyes)
28958
The evolution of the different skin colors is thought to have occurred as follows: the haired ancestor of humans, like modern great apes, had light skin under their hair. Once the hair was lost, they evolved dark skin, needed to prevent low folate levels since they lived in sun-rich Africa. (The skin cancer connection is probably of secondary importance, since skin cancer usually kills only after the reproductive age and therefore doesn't exert much evolutionary pressure.) When humans migrated to sun-poorer regions in the north, low vitamin D3 levels became a problem and light skin color evolved.\n\nDark-skinned people who live in sun-poor regions often lack vitamin D3, one reason for the fortification of milk with vitamin D in some countries.\n\nThe Inuit are a special case: even though they live in an extremely sun-poor environment, they have retained their relatively dark skin. This can be explained by the fact that their traditional animal-based diet provides plenty of vitamin D.\n\nAlbinism is a condition characterized by the absence of melanin, resulting in white skin and hair; it is caused by a genetic mutation.\n\nResearch on skin color variability:\nThe color of human skin varies from dark brown to pale pink. In attempting to discover the mechanisms that have generated such a wide variation in human skin color, Nina Jablonski and George Chaplin (2000) discovered that there is a high correlation between the coloration of the human skin of indigenous peoples and the average annual ultraviolet (UV) radiation available for skin exposure where the indigenous peoples live. Accordingly, Jablonski and Chaplin plotted the whiteness (W) of skin coloration of indigenous peoples who have stayed in the same geographical area for the last 500 years versus the annual UV available for skin exposure (AUV) for over 200 indigenous persons and found that whiteness W of skin coloration is related to to the annual UV available for skin exposure AUV according to\n\n    W = 70 - [(AUV)/(10)]\n\n(Jablonski and Chaplin (2000), p. 67, formula coefficients have been rounded to one-figure accuracy) where the whiteness W of skin coloration is measured as the percentage of light reflected from the upper inner arm at which location on humans there should be minimal tanning of human skin due to personal exposure to the sun; a lighter skinned human would reflect more light and would have a higher W number. Judging from the above linear fit to the empirical data, the theoretical maximum whitest human skin would reflect only 70 per cent of incident light for a hypothetical indigenous human-like population that lived where there was zero annual UV available for skin exposure (AUV = 0 in the above formula). Jablonski and Chaplin evaluated average annual UV available for skin exposure AUV from satellite measurements that took into consideration the measured daily variation in the thickness of the ozone layer that blocked UV hitting the earth, measured daily variation in opacity of cloud cover, and daily change in angle at which the sunlight containing UV radiation strikes the earth and passes through different thicknesses of earth's atmosphere at different latitudes for each of the different human indigenous peoples' home areas from 1979 to 1992.\n\nJablonski and Chaplin proposed an explanation for the observed variation of untanned human skin with annual UV exposure. By Jablonski and Chaplin's explanation, there are two competing forces affecting human skin color:\n\n   1. the melanin that produces the darker tones of human skin serves as a light filter to protect against too much UV light getting under the human skin where too much UV causes sunburn and disrupts the synthesis of precursors necessary to make human DNA; versus\n   2. humans need at least a minimum threshold of UV light to get deep under human skin to produce vitamin D, which is essential for building and maintaining the bones of the human skeleton.\n\nJablonski and Chaplin
84807
Take a look at the Innuit (eskimos). Their skin is dark. People of Siberia have darker skin than Europeans. I think its more a matter of genetics than the amount of melanin.
807689
They appear dark because they are very thick clouds and obscure sunlight from getting through. If viewed from above, they appear pure white.
535130
Dark skinned (tanned) are MUCH hotter.
474523
There are some great maps out there correlating skin tone with a modeled optimum at each geographic point.  That optimum is based on balancing the need to avoid burning and skin cancer against the need to obtain UV light for creation of vitamin D.  \n\nOther adaptations relate to features of the environment.  Northern Europeans, Inuit, and Eskimo people have a distribution of fat on their bodies that is optimized for heat retention.  The body shape of a Masai, for example, would be less than optimal near the North Pole.\n\nThere is a hypothesis that many traits are associated with sexual selection or may pertain to the tradeoff between sexual selection and aspects of the environment.  The distribution of fat tissue, particularly in women, in different races has been proposed as correlated with cultural differences in male preference as well as with adaptaion to the local environment.\n\nFinally, there is the feature of accident.  The epicanthal fold of many East Asians might have been beneficial to many Caucasians, but perhaps by chance the feature simply wasn't present in founding populations in Europe.  Characteristics in founding population and gained or lost by chance certainly play a big role in differences in humans from different geographic areas.  Not everythig is adaptive.\n\nBear in mind that this is not based on fixed differences among populations or races of humans, but instead on gene frequency in different populations.  For example, Swedes are lighter in skin color than the Ndebele not because each population has distinct genes, but because those genes differ in frequency.  Among all the loci that contribute to skin color, Swedish populations have very few alleles that code for dark skin.  Each individual Swede will therefore have only a few dark loci where dark alleles are present whereas most loci will have light alleles.  The Ndebele populations and individuals would act in reverse.
727102
Perhaps because they use the color to attract females.  Or, since females are more essential to reproduction, it is beneficial for the females to blend in with the environment to avoid predators.