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181 lines
8.0 KiB
Plaintext
ÜÜÜÜÜÜÜÜÜÜÜÜÜ ÜÜÜ ÜÜÜÜ
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ÜÛÛÛÛÛÛÛÛßÛßßßßßÛÛÜ ÜÜßßßßÜÜÜÜ ÜÛÜ ÜÛÛÛÛÛÛÛÛÜÜÜÜÜÛßß ßÛÛ
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ßÛÛÛÛÛÛÛÛÛÛÛÛÛÛÜ ßÛÛ ÜÛÛÛÜÛÛÜÜÜ ßÛÛÛÛÜ ßÛÛÛÛÛÛÛÜÛÛÜÜÜÛÛÝ Ûß
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ßßßÛÛÛÛÛÛÛÛÛÛÜ ÞÝ ÛÛÛÛÛÛÛÛÛÛÛßßÛÜÞÛÛÛ ÛÛÛÛÛÜ ßßÛÛÛÞß
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Mo.iMP ÜÛÛÜ ßÛÛÛÛÛÛÛÝÛ ÞÛÛÛÛÛÛÛÛÛ ÞÛÛÛÛ ÞÛÛÛÛÛÝ ßÛß
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ÜÛÛÛÛÛÛÛ ÛÛÛÛÛÛÛÛÝ ÞÛÛÛÛÛÛÛÛÝ ÛÛÛ ÛÛÛÛÛÛ
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ÜÛÛÛÛÛÛÛÝ ÞÛÛÛÛÛÛÛÛ ÞÛÛÛÛÛÛÛÛ ß ÞÛÛÛÛÛÛÜ ÜÛ
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ÜÛÛÛÛÛÛÛÝ ÛÛÛÛÛÛÛÛ ÛÛÛÛÛÛÛÛÝ ÞÞÛÛÛÛÛÛÛÛÛß
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ÜÛßÛÛÛÛÛÛ ÜÜ ÛÛÛÛÛÛÛÛÝ ÛÛÞÛÛÛÛÛÝ ÞÛÛÛÛÛÛßß
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ÜÛßÛÛÛÛÛÛÜÛÛÛÛÜÞÛÛÛÛÛÛÛÛ ÞÛ ßÛÛÛÛÛ Ü ÛÝÛÛÛÛÛ Ü
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ÜÛ ÞÛÛÛÛÛÛÛÛÛÛß ÛÛÛÛÛÛÛÛÛ ßÛÜ ßÛÛÛÜÜ ÜÜÛÛÛß ÞÛ ÞÛÛÛÝ ÜÜÛÛ
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ÛÛ ÛÛÛÛÛÛÛÛß ÛÛÛÛÛÛÛÛÛÛÜ ßÛÜ ßßÛÛÛÛÛÛÛÛÛß ÜÜÜß ÛÛÛÛÜÜÜÜÜÜÜÛÛÛÛÛß
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ßÛÜ ÜÛÛÛß ßÛÛÛÛÛÛÛÛÛÛÜ ßßÜÜ ßßÜÛÛßß ßÛÛÜ ßßßÛßÛÛÛÛÛÛÛßß
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ßßßßß ßßÛÛß ßßßßß ßßßßßßßßßßßßß
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ARRoGANT CoURiERS WiTH ESSaYS
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Grade Level: Type of Work Subject/Topic is on:
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[ ]6-8 [ ]Class Notes [General Information on ]
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[ ]9-10 [ ]Cliff Notes [Penguins ]
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[x]11-12 [ ]Essay/Report [ ]
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[ ]College [x]Misc [ ]
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Dizzed: 09/94 # of Words:1046 School: ? State: ?
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ÄÄÄÄÄÄÄÄÄ>ÄÄÄÄÄÄÄÄÄ>ÄÄÄÄÄÄÄÄÄ>Chop Here>ÄÄÄÄÄÄÄÄÄ>ÄÄÄÄÄÄÄÄÄ>ÄÄÄÄÄÄÄÄÄ>ÄÄÄÄÄÄÄÄÄ
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==================================================
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Penguins: the eyes have it! LIFE SCIENCES
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--------------------------------------------------
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Myopic little men in tuxedos, or highly efficient
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land/water animals? Recent research indicates
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there's more to penguins than meets the eye.
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If you've every wondered what it would be like to
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be able to see as clearly under water as you can on
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land, just ask the nearest penguin.Most aquatic
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animals are short-sighted on land. Most
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terrestrial animals (and that includes us) are
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far-sighted under water. But researchers have
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discovered that penguins can apparently see equally
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well in both environments, because of the unique
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structure of their eyes.
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Penguins have to be able to see well under water
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because their diet consists mainly of plankton,
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molluscs, crustaceans, and the inevitable fish.
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Through a special slowing-down of their heart rate
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they're able, like many other diving animals, to
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stay submerged long enough to search out and chase
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whatever catches their fancy.
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On dry land, it's a different story-or has been up
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to now. Waddling along on their flat little feet,
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eyes fixed intently on the ground, penguins appear
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myopic, inefficient and generally out of place.
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In fact the reverse is true. During a recent stay
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on the Falkland Islands, a Canadian researcher
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discovered that penguins are able to recognize
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individuals and navigate the rocky terrain on which
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they live quite well. Long of body and short of
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leg, they probably poke their heads forward as an
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aid to balance. And as for looking at the ground,
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they're merely-like us-keeping an eye on where
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they're going.
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The human eye is adapted for aerial vision, which
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is why scuba divers-or even you and I in the local
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swimming pool-must wear goggles or a face mask to
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re-introduce air in front of our eyes in order to
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see clearly.
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Among vertebrates in general, the bird eye is
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frequently described as the most efficient. Its
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superior quality, combined with the fact that a
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large number of birds-cormorants, pelicans,
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seagulls, even ducks, as well as penguins-get their
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food from water, obviously deserved research beyond
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that possible in a controlled environment such as
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an aquarium or zoo. Professor Jacob Sivak of the
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University of Waterloo and his associate, Professor
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Howard Howland of Cornell University, had a chance
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to do that research recently. Their trip had but
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one purpose-to study the structure of penguins'
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eyes while observing their natural habitat.
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The Falkland Islands, off the coast of Argentina,
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offered this opportunity, being one the few areas
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outside Antarctica where penguins can be found in
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large numbers. Three of the 16 known species were
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located there: the Gentoo, which live on flat
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areas right off the beach; the Magellan (also
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called Jackass), which live in burrows; and the
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Rock-hoppers, which live among the rocks along the
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cliffs.
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The Rock-hoppers were by far the most common,
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having a population of well over 100,000. The
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general rule is, the smaller the penguin, the
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meaner the temperament, and the researchers did
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witness the odd fight. Their flippers may look
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pretty useless out of water, but it's not smart to
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play around with a penguin. Hel'll stand his
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ground in a face-off and if you're foolish enough
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to get too close, those flippers can knock you
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flat.
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Dr. Sivak and his associate, however, had little
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trouble. Rock-hoppers always congregate in fairly
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tight groups, as a defense against predatory birds
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such as the skua (a large seagull that thinks it's
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a hawk), and two more upright figures in their
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midst didn't seem to bother them.
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Standing as close to their subjects as 0.3m, the
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scientists used two devices: one, developed by
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Professor Howland, to take photographs of the
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penguins' eyes; the othger, developed by Dr. Sivak,
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to shine a series of concentric circles on the
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cornea and give a measurement of how reflections of
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objects are altered by curvature of the eye.
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Despite the fact all the work had to be done at
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night-the only time the penguins' pupils were
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dilated enough-the results were worth it.
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Comparison of the photographs with similar photos
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of human eyes, and study of the internal structure
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of the eyes of creatures discovered killed by seal
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lions, proved the scientists' theory that the
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penguin's eyes are the secret of its survival.
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In general terms, a penguin eye and a human eye are
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almost identical. Both have the same components
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necessary for vision-a cornea through which light
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can enter; an iris which controls the amount of
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light that enters; and a crystalline lens that
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focuses the light onto the back of the eye where a
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specialized membrane, the retina, receives it and
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passes the message along the optic nerve to the
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brain for interpretation.
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In the penguin eye, hoever, there are many subtle
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differences. The cornea, for example, is markedly
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flattened compared to ours -- so much so that it
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almost resembles a window-pane. This greatly
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alters the angle at which light can enter the eye
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and is very important for underwater swimming, when
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light enters the eye obliquely through a medium
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(water) whose density is quite different to the
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density of air.
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The penguin iris is controlled by a very powerful
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muscle which is able to drastically alter the shape
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of the lens attached to it, depending on whether
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the penguin is in or out of the water. The lens,
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comparatively larger than ours and differently
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shaped, focuses the light coming through the
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flattened cornea onto the retinal body at the back
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of the eye. In this way, the penguin eye adapts to
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whatever medium it happens to be in at the time.
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Interestingly, there was no evidence of eye
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problems (apart from one incident of blindness due
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to injury) in the group of penguins studied. Of
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course penguins don't read, watch TV or encounter
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any of the numerous irritants we land-bound animals
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subject ourselves-or are subjected-to during our
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lifetime.
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Both the testing devices and methods used in this
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study are easily adaptable for use with human eyes,
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paving the way for fast, easy identification of eye
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problems. Also, the researchers hope that the
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insights they've gained into how animals deal with
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two environments may lead to knowledge of how humans,
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in the future, might do likewise.
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==================================================
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PENGUINS (C) 1987 Ontario Science Centre.
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May be duplicated for use on other information
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services with permission.
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==================================================
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