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Animals on the Move
A)
It looked like a scene from “Jaws” but without the
dramatic music. A huge shark
was slowly
swimming through the water, its tail swinging back
and forth like the pendulu
m of a clock.
Suddenly sensitive nerve ending in the
shark?s skin picked up vibrations of
a struggling fish. The shark was
immediately transformed into a deadly, efficient
machine
of death. With muscles taut,
the shark knifed through the water at a rapid
speed. In a fl
ash the shark caught its
victim, a large fish, in its powerful jaws. Then,
jerking its head b
ack and forth, the
shark tore huge chunks of flesh from its victim
and swallowed them. S
oon the action was
over.
Moving to Survive
B) In pursuing
its prey, the shark demonstrated in a dramatic way
the important role
of movement, or
locomotion, in the shark, most animals use
movement to f
ind also use locomotion
to escape enemies, find a mate, and explore new
terri
tories. The methods of locomotion
include crawling, hopping, slithering, flying,
swimming,
or have the added advantage
of using their various inventions to move
about in just about any kind of
environment. Automobiles, rockets, and submarines
trans
port humans from deep oceans to as
far away as the r, for other animals
movement came about naturally through
millions of years of evolution. One of the most
successful examples of animal
locomotion is that of the shark. Its ability to
quickly zero i
n on its prey has always
impressed scientists. But it took a detailed study
by Duke Univer
sity marine biologists S.
A. Wainwright, F. Vosburgh, and J. H. Hebrank to
find out how t
he sharks did it. In
their study the scientists observed sharks
swimming in a tank at Mari
ne land in
Saint Augustine, Fla. Movie
s were taken
of the sharks? movements and analyze
d.
Studies were also made of shark skin and muscle.
Skin Is the Key
C) The
biologists discovered that the skin of the shark
is the key to the animal?s high
efficiency in swimming through the water. The skin
contains many fibers that crisscross
l
ike the inside of a belted radial
tire. The fibers are called collagen fibers. These
fibers can
either store or release
large amounts of energy depending on whether the
fibers are rel
axed or taut. When the
fibers are stretched, energy is stored in them the
way energy is s
tored in the string of a
bow when pulled tight. When the energy is
released, the fibers be
come relaxed.
D)
The Duke University biologists have found that the
greatest stretching occurs wh
ere
the shark bends its body while
swimming. During the body?s back and forth motion,
f
ibers along the outside part of the
bending body stretch greatly. Much potential
energy is
stored in the
fibers. This energy is released when the shark?s
body snaps back th
e other
way.
As energy is alternately
stored and released on both sides of the animal?s
body, the t
ail whips strongly back and
forth. This whip-like action propels the animal
through the w
ater like a living bullet.
Source of Energy
E) What causes
the fibers to store so much energy? In finding the
answer the Duke
University scientists
learned that the shark?s similarity to a belted
radial tire doesn?t stop
with the skin.
Just as a radial tire is inflated by pressure, so,
too, is the area just under t
he shark?s
collagen “radials”. Instead of air pressure,
however, the pressure in the shark
may
be due to the force of the blood pressing on the
collagen fibers.
F) When the shark swims
slowly, the pressure on the fibers is relatively
low. The fibe
rs are more relaxed, and
the shark is able to bend its body at sharp
angles. The animal s
wims this way when
looking around for food or just swimming. However,
when the shark
detects an important
food source, some fantastic involuntary changes
take place. The pr
essure inside the
animal may increase by 10 times. This pressure
change greatly stretche
s the fibers,
enabling much energy to be stored. This energy is
then transferred to the tai
l, and the
shark is off. The rest of the story is
predictable.
Dolphin Has Speed Record
G) Another fast
marine animal is the dolphin. This seagoing mammal
has been clock
ed at speeds of 32
kilometers (20 miles) an hour. Biologists studying
the dolphin have dis
covered that, like
the shark, the animal?s efficient
locomotio
n can be traced to its skin. A
dolphin?s skin is made up in such a way
that it offers very little resistance to the water
flo
wing over it. Normally when a fish
or other object moves slowly through the water,
the w
ater flows smoothly past the body.
This smooth flow is known as laminar flow.
However,
at faster speeds the water
becomes more turbulent along the moving fish. This
turbulenc
e muses friction and slows the
fish down.
H) In a dolphin the skin is so flexible
that it bends and yields to the waviness of the
water. The waves, in effect, become
tucked into the skin?s folds. This allows the rest
of t
he water to move smoothly by in a
laminar flow. Where other animals would be slowed
b
y turbulent water at rapid speeds, the
dolphin can race through the water at record
brea
king speeds.
Other Animals
Less Efficient
I) Not all animals move as
efficiently as sharks and dolphins. Perhaps the
greatest lo
ser in locomotion efficiency
is the slug. The slug, which looks like a snail
without a shell, l
ays down a slimy
trail over which it crawls. It uses so much energy
producing the slimy
mucus and crawling
over it that a mouse traveling the same distance
uses only one twelf
th as much energy.
Scientists say that because of the slug?s
inefficient use of en
ergy, its
l
ifestyle must be restricted. That is,
the animals are forced to confine themselves to
small
areas for obtaining food and
finding proper living conditions. Have humans ever
been fa
ced with this kind of problem?
我要找茬
1
1.
According to
the passage, a shark can use movement to find
food, to avoid being cha
sed by its
enemies, and to find a new place to live.
选择答案：
< br>A
B
C
D
E
F
G
H
I
2.
2
Examples of
automobiles, rockets and submarines are used to
show that human inve
ntions enable us to
travel in almost any kind of environment.
选择答案：
A
B
C
D
E
F
G
H
I
J
3.
The
skin is the key to the shark?s swift locomotion in
water.
选择答案：
A
B
C
D
E
F
G
H
I
< br>
44
(4)
444
According to the Duke University scientists, when bending its body in swimming,
the
shark stretch its collagen fibers to the greatest
extent
选择答案：
A
B
C
D
E
F
G
H
I
5.
Because it is
also inflated by pressure, the area just under the
shark?s collagen fibers
similar to a
belted radial tire.
选择答案：
A
B
C
D
E
F
G
H
6.
6
A laminar
flow is formed when a fish swims slowly through
the water.
选择答案：
A
B
C
D
E
F
G
H
77
7
7
Consuming the
equal amount of energy as a slug does, a mouse can
travel 12 t
imes as long as a slug.
选择答案：
8
A
B
C
D
E
F
G
H
I
8.A shark finds its prey by
feeling the vibrations of a struggling prey.
选择答案：
A
B
C
D
E
F
G
H
I
9.
9
According to
the passage, collagen fibers can be compared to
the string of
a bow for both of them
store energy when stretched.
选择答案：
A
B
C
D
E
F
G
H
I
10
the shark
detects an important food source, some fantastic
involuntar
y changes take place.
选择答案：
A
B
C
D
E
F
G
H
I
7
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