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Реферат: PenguinsA Essay Research Paper Penguins VisionRecent research

Название: PenguinsA Essay Research Paper Penguins VisionRecent research
Раздел: Топики по английскому языку
Тип: реферат Добавлен 03:05:23 04 ноября 2010 Похожие работы
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Penguins(A) Essay, Research Paper

Penguins VisionRecent research indicates there’s more to penguins than meets the eye. If you’ve every wondered what it would be like tobe able to see as clearly under water as you can onland, just ask the nearest penguin. Most aquaticanimals are short-sighted on land. Mostterrestrial animals (and that includes us) arefar-sighted under water. But researchers havediscovered that penguins can apparently see equallywell in both environments, because of the uniquestructure of their eyes. Penguins have to be able to see well under waterbecause their diet consists mainly of plankton,molluscs, crustaceans, and the inevitable fish.Through a special slowing-down of their heart ratethey’re able, like many other diving animals, tostay submerged long enough to search out and chasewhatever catches their fancy. On dry land, it’s a different story-or has been upto now. Waddling along on their flat little feet,eyes fixed intently on the ground, penguins appearmyopic, inefficient and generally out of place. In fact the reverse is true. During a recent stayon the Falkland Islands, a Canadian researcherdiscovered that penguins are able to recognizeindividuals and navigate the rocky terrain on whichthey live quite well. Long of body and short ofleg, they probably poke their heads forward as anaid to balance. And as for looking at the ground,they’re merely-like us-keeping an eye on wherethey’re going. The human eye is adapted for aerial vision, whichis why scuba divers-or even you and I in the localswimming pool-must wear goggles or a face mask tore-introduce air in front of our eyes in order tosee clearly. Among vertebrates in general, the bird eye isfrequently described as the most efficient. Itssuperior quality, combined with the fact that alarge number of birds-cormorants, pelicans,seagulls, even ducks, as well as penguins-get theirfood from water, obviously deserved research beyondthat possible in a controlled environment such asan aquarium or zoo. Professor Jacob Sivak of theUniversity of Waterloo and his associate, ProfessorHoward Howland of Cornell University, had a chanceto do that research recently. Their trip had butone purpose-to study the structure of penguins’eyes while observing their natural habitat. The Falkland Islands, off the coast of Argentina,offered this opportunity, being one the few areasoutside Antarctica where penguins can be found inlarge numbers. Three of the 16 known species werelocated there: the Gentoo, which live on flatareas right off the beach; the Magellan (alsocalled Jackass), which live in burrows; and theRock-hoppers, which live among the rocks along thecliffs. The Rock-hoppers were by far the most common,having a population of well over 100,000. Thegeneral rule is, the smaller the penguin, themeaner the temperament, and the researchers didwitness the odd fight. Their flippers may look

pretty useless out of water, but it’s not smart toplay around with a penguin. Hel’ll stand hisground in a face-off and if you’re foolish enoughto get too close, those flippers can knock youflat. Dr. Sivak and his associate, however, had littletrouble. Rock-hoppers always congregate in fairlytight groups, as a defense against predatory birdssuch as the skua (a large seagull that thinks it’sa hawk), and two more upright figures in theirmidst didn’t seem to bother them. Standing as close to their subjects as 0.3m, thescientists used two devices: one, developed byProfessor Howland, to take photographs of thepenguins’ eyes; the othger, developed by Dr. Sivak,to shine a series of concentric circles on thecornea and give a measurement of how reflections ofobjects are altered by curvature of the eye. Despite the fact all the work had to be done atnight-the only time the penguins’ pupils weredilated enough-the results were worth it.Comparison of the photographs with similar photosof human eyes, and study of the internal structureof the eyes of creatures discovered killed by seallions, proved the scientists’ theory that thepenguin’s eyes are the secret of its survival. In general terms, a penguin eye and a human eye arealmost identical. Both have the same componentsnecessary for vision-a cornea through which lightcan enter; an iris which controls the amount oflight that enters; and a crystalline lens thatfocuses the light onto the back of the eye where aspecialized membrane, the retina, receives it andpasses the message along the optic nerve to thebrain for interpretation. In the penguin eye, hoever, there are many subtledifferences. The cornea, for example, is markedlyflattened compared to ours — so much so that italmost resembles a window-pane. This greatlyalters the angle at which light can enter the eyeand is very important for underwater swimming, whenlight enters the eye obliquely through a medium(water) whose density is quite different to thedensity of air. The penguin iris is controlled by a very powerfulmuscle which is able to drastically alter the shapeof the lens attached to it, depending on whetherthe penguin is in or out of the water. The lens,comparatively larger than ours and differentlyshaped, focuses the light coming through theflattened cornea onto the retinal body at the backof the eye. In this way, the penguin eye adapts towhatever medium it happens to be in at the time. Interestingly, there was no evidence of eyeproblems (apart from one incident of blindness dueto injury) in the group of penguins studied. Ofcourse penguins don’t read, watch TV or encounterany of the numerous irritants we land-bound animalssubject ourselves-or are subjected-to during ourlifetime. Both the testing devices and methods used in thisstudy are easily adaptable for use with human eyes,paving the way for fast, easy identification of eyeproblems. Also, the researchers hope that theinsights they’ve gained into how animals deal withtwo environments may lead to knowledge of how humans,in the future, might do likewise.


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