rt Ill: Considering the Evolutionary Adaptations of the Visible s trum of the Hu
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rt Ill: Considering the Evolutionary Adaptations of the Visible s trum of the Human Eye Pa The mechanism by which living creatures 'see' the world around them vary signißicastly acroes species. Even more remarkably, this diversity Hum of evolutionary adaptations exists even though all living things were ex- posed to the same ultimate source: the Sun. The solar spectrum is, in fact, very diflerent from the spectrum to which the human eye is sensi- tive (often ealled the 'visible' spectram). Many Insects and some birds are sensitive to the wavelengths, partieularly in the ultraviolet, that are completely invisible to the haman eye (thoagh human skin is sensitive to these wavelengths!); thus, the visible spectrum of a bee or a bird can be quite diferent from that of a human. Bees, birds, turtles, lizards, many fish, and some rodents have UV receptors in thelr retinas. These animals can see the UV patterns found on Blowers and other wildlife that are otherwise invisible to the buman eye? Bee the u The Schlieren photograph above shows the sones of a fish lens that fo- cusses different spectral ranges (red on the outside edge, toward UV at the center). Some animals such as reptiles (e.g snalkes), have IR (infra red) sensitivity. Why have humans developed eyes sensitive only to the visible spec- trum (between about 400 m and 700 nm)? Why are the UV and IR bands, present in the solar spectrum and in the visible spectra of other living creatures, absent form the visible spectrum of the human eye? Your task is 1) to develop plausible hypotheses for the evo- lutionary adaptations resulting in the absence of UV and IR sensitivity in the human eye and 2) to collect spectral data in support of the plausibility of your hypothesis. The following two charts may (or may not) help you get started in thinking about plausible hypotheses. Solar Spectnume Outside Armoxphere&As Sea Levelw/ KO Absorp Prom: http:/ww.webexhibits.org/eauesodoolot/17.btml Prom Wikipedia: http//en.wikipedia.org/wilki/Color.visionther animal.apeclesExplanation / Answer
human can see only visible part of electromagnetic spectrum due to presence of rods and cones cells in the retina which play an important role in dark and light vision respectively; since there is not any mutation, if there is mutation occur, this is not favorable for them, hence unable to see UV nd IR light.
but for other creatures like snakes, birds has receptor for UV AND IR receptor in addition with rods and cones in retina. Thats why they can see UV and IR region with visible region.
WHY THESE HAPPEN?
in those creature, mutation was happened in past in their retinal cells , not only mutation is necessary but there was also advantage of that mutation to creature and hence due to natural selection these mutrated organis favour more as compared to other hence these mutation are geneticallly fixed and anle to see UVand IR region of spectrum.
As in mutated retina birds, these UV receptor helpful in foraging, orientation and signalling. so it is more favourable than normal birds. hence fixed in their genetic materal and adapt these character during lon time of evolution.
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