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Реферат: Penguins Essay Research Paper PenguinsMyopic little men

Название: Penguins Essay Research Paper PenguinsMyopic little men
Раздел: Топики по английскому языку
Тип: реферат Добавлен 08:21:09 10 ноября 2010 Похожие работы
Просмотров: 6 Комментариев: 20 Оценило: 2 человек Средний балл: 5 Оценка: неизвестно     Скачать

Penguins Essay, Research Paper


Myopic little men in tuxedos, or highly efficient

land/water animals? Recent research indicates

there’s more to penguins than meets the eye.

If you’ve every wondered what it would be like to

be able to see as clearly under water as you can on

land, just ask the nearest penguin.Most aquatic

animals are short-sighted on land. Most

terrestrial animals (and that includes us) are

far-sighted under water. But researchers have

discovered that penguins can apparently see equally

well in both environments, because of the unique

structure of their eyes.

Penguins have to be able to see well under water

because their diet consists mainly of plankton,

molluscs, crustaceans, and the inevitable fish.

Through a special slowing-down of their heart rate

they’re able, like many other diving animals, to

stay submerged long enough to search out and chase

whatever catches their fancy.

On dry land, it’s a different story-or has been up

to now. Waddling along on their flat little feet,

eyes fixed intently on the ground, penguins appear

myopic, inefficient and generally out of place.

In fact the reverse is true. During a recent stay

on the Falkland Islands, a Canadian researcher

discovered that penguins are able to recognize

individuals and navigate the rocky terrain on which

they live quite well. Long of body and short of

leg, they probably poke their heads forward as an

aid to balance. And as for looking at the ground,

they’re merely-like us-keeping an eye on where

they’re going.

The human eye is adapted for aerial vision, which

is why scuba divers-or even you and I in the local

swimming pool-must wear goggles or a face mask to

re-introduce air in front of our eyes in order to

see clearly.

Among vertebrates in general, the bird eye is

frequently described as the most efficient. Its

superior quality, combined with the fact that a

large number of birds-cormorants, pelicans,

seagulls, even ducks, as well as penguins-get their

food from water, obviously deserved research beyond

that possible in a controlled environment such as

an aquarium or zoo. Professor Jacob Sivak of the

University of Waterloo and his associate, Professor

Howard Howland of Cornell University, had a chance

to do that research recently. Their trip had but

one 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 areas

outside Antarctica where penguins can be found in

large numbers. Three of the 16 known species were

located there: the Gentoo, which live on flat

areas right off the beach; the Magellan (also

called Jackass), which live in burrows; and the

Rock-hoppers, which live among the rocks along the


The Rock-hoppers were by far the most common,

having a population of well over 100,000. The

general rule is, the smaller the penguin, the

meaner the temperament, and the researchers did

witness the odd fight. Their flippers may look

pretty useless out of water, but it’s not smart to

play around with a penguin. Hel’ll stand his

ground in a face-off and if you’re foolish enough

to get too close, those flippers can knock you


Dr. Sivak and his associate, however, had little

trouble. Rock-hoppers always congregate in fairly

tight groups, as a defense against predatory birds

such as the skua (a large seagull that thinks it’s

a hawk), and two more upright figures in their

midst didn’t seem to bother them.

Standing as close to their subjects as 0.3m, the

scientists used two devices: one, developed by

Professor Howland, to take photographs of the

penguins’ eyes; the othger, developed by Dr. Sivak,

to shine a series of concentric circles on the

cornea and give a measurement of how reflections of

objects are altered by curvature of the eye.

Despite the fact all the work had to be done at

night-the only time the penguins’ pupils were

dilated enough-the results were worth it.

Comparison of the photographs with similar photos

of human eyes, and study of the internal structure

of the eyes of creatures discovered killed by seal

lions, proved the scientists’ theory that the

penguin’s eyes are the secret of its survival.

In general terms, a penguin eye and a human eye are

almost identical. Both have the same components

necessary for vision-a cornea through which light

can enter; an iris which controls the amount of

light that enters; and a crystalline lens that

focuses the light onto the back of the eye where a

specialized membrane, the retina, receives it and

passes the message along the optic nerve to the

brain for interpretation.

In the penguin eye, hoever, there are many subtle

differences. The cornea, for example, is markedly

flattened compared to ours — so much so that it

almost resembles a window-pane. This greatly

alters the angle at which light can enter the eye

and is very important for underwater swimming, when

light enters the eye obliquely through a medium

(water) whose density is quite different to the

density of air.

The penguin iris is controlled by a very powerful

muscle which is able to drastically alter the shape

of the lens attached to it, depending on whether

the penguin is in or out of the water. The lens,

comparatively larger than ours and differently

shaped, focuses the light coming through the

flattened cornea onto the retinal body at the back

of the eye. In this way, the penguin eye adapts to

whatever medium it happens to be in at the time.

Interestingly, there was no evidence of eye

problems (apart from one incident of blindness due

to injury) in the group of penguins studied. Of

course penguins don’t read, watch TV or encounter

any of the numerous irritants we land-bound animals

subject ourselves-or are subjected-to during our


Both the testing devices and methods used in this

study are easily adaptable for use with human eyes,

paving the way for fast, easy identification of eye

problems. Also, the researchers hope that the

insights they’ve gained into how animals deal with

two environments may lead to knowledge of how humans,

in the future, might do likewise.

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