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cbrd7
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module15
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1992-01-01
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208 lines
NEW SET
A
The blood of the horseshoe crab was found, in the 1960s, to be
highly valuable because it reacts with, and so can be used to detect,
bacterial endotoxin, a dangerous poison produced by some infectious
bacteria that can bring on fever, pain, inflammation, shock - and
sometimes death.
A substance in this blood also reacts with the red and white cells
in the human blood, particularly the cancerous white cells of some
leukemia patients. One day it may be used for diagnosing this illness.
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1
1. The blood of the horseshoe crab is valuable to:
A. drug manufacturers
B. chemists
C. leukemia patients
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A
0
B
Correct.
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wrong answer explanation
B
(A) Drug manufacturers may use this blood to make life-saving drug products.
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NEW SET
B
In their forays into the surf, the collectors capture horseshoe
crabs measuring almost a foot across the thick frontal helmet, through
which the animal peers out at its world with seven eyes, set in four
concealed peekholes. Mature crabs crawl ashore on summer high tides to
deposit their eggs in the sand. They spend most of their lives in the
nearby shallows, going deeper in winter. Oddly, all four horseshoe crab
species inhabit only the eastern edges of the continental land masses
of North America and Asia.
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1
1. Horseshoe crabs are not found in the waters off:
A. Maine
B. Japan
C. Yucatan
D. Chile
E. China
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D
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C
Correct.
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wrong answer explanation
C
(D) They are not found along North America's western coastline, which
includes Chile.
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NEW SET
C
The horseshoe crab is not a crab at all, but belongs to the spider
class, Arachnida. It appears to be most closely related to scorpions -
though its tail is stingless - and to ancient trilobites, whose form
it recapitulates in the larval stage.
Horseshoe crabs originated some 400 million years ago. "It's an
animal that's been made to stay around," says Dr. Cohen, an immunologist
who has been a leader in biomedical research involving the animal and in
efforts to protect this unusual creature.
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1
1. The horseshoe crab is:
A. a mammal
B. a spider
C. one of the last prehistoric animals
D. a trilobite
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C
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D
Correct.
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wrong answer explanation
D
(C) It is one of few surviving prehistoric animals.
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NEW SET
D
To obtain the blood, commercial collectors place the animal on a
rack, push a hypodermic needle into the horseshoe crab's heart, attach
a tube, then collect the blood that drains slowly out by gravity in a
sterile container. The blood has a striking royal blue hue because
its oxygen-carrying molecule, hemocyanin, contains copper instead of
iron (which gives red blood its color). Depending on the animal's size,
it will give up one to seven ounces of blood in this way.
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1
1. Hemocyanin:
A. is blue
B. contains blood
C. contains iron
D. is an oxygen-carrying molecule
E. is found only in the heart of a horseshoe crab
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D
0
E
Correct.
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wrong answer explanation
E
(D) Hemocyanin molecules carry oxygen.
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NEW SET
E
"They don't seem to react too badly," says Dr. Rudloe. "When we
take them out of the racks, they move about fairly vigorously."
FDA, she says, requires that bled crabs be returned to salt water
within 72 hours and, as far as anyone knows, most survive their blood
loss. But no one knows for sure, and Rudloe's study is the first attempt
to assess their recovery - or lack of it - in a scientific way.
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1
1. After being bled, horseshoe crabs:
A. live for 72 hours
B. move about vigorously, then die
C. are protected by the FDA
D. must be returned to the ocean if they are to survive
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D
0
F
Correct.
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wrong answer explanation
F
(D) They are returned to the ocean.
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NEW SET
F
Industrially polluted water appears to kill horseshoe crabs. But
the very traits that make the animal medically valuable also protect
it against most pollutants, and it continues to thrive in sewage-laden
harbors of both the United States and Japan. In fact, the species'
internal system of defense against invading bacteria is impressive.
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1
1. Pollutants of any kind kill horseshoe crabs.
A. True
B. False
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B
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G
Correct.
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wrong answer explanation
G
(B) Horseshoe crabs can survive in polluted waters.
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NEW SET
G
Horseshoe crabs lack an immune system, the multi-targeting defense
method that allows modern animals to produce antibodies directed at
specific bacterial species and many - perhaps millions - of other
menacing alien molecules. By contrast, the horseshoe crab's primitive
but extremely potent defense system seeks out a handful of key biochemical
molecules that are constituents of most bacteria that may infect them.
This remarkable self-protective method has captivated biomedical
scientists.
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1
1. The horseshoe crab is studied because of its defense system.
A. True
B. False
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A
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H
Correct.
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wrong answer explanation
H
(A) Biomedical scientists study its defense system.
END