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The tsetse fly, belonging to any of

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The tsetse fly, belonging to any of  [#permalink] New post 20 Nov 2010, 19:45
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The tsetse fly, belonging to any of approximately twenty species
composing the genus Glossina, is indigenous to Africa and is found
primarily in forests and savannahs south of the Tropic of Cancer.
Dependent on vertebrate blood for nourishment, the tsetse fly is
equipped with a long proboscis which is sharp enough to penetrate most
animal skins and powerful enough to enable the tsetse to drink quantities
of blood up to three times its own body weight.

At the same time that the tsetse drains blood, it can also transmit a
variety of dangerous diseases. A bite from a tsetse fly can induce African
sleeping sickness in human beings and nagana, a similar ailment, in
domestic livestock. The agent of these diseases is the trypanosome, a
unicellular, flagellated parasite which feeds primarily on the blood of
vertebrates and is generally transmitted by an intermediary leech or
insect host, such as the tsetse fly. In humans the trypanosome causes
damage to the brain and spinal cord, leading to extreme lethargy and,
ultimately, death; in livestock, trypanosomes destroy red blood cells,
causing fatal anaemia.

The immune system is ill-equipped to counter trypanosomes. As the
immune system attempts to counter disease, antibodies are produced to
attack microbes whose antigens, surface proteins, are foreign to the
body. However, the trypanosome is capable of disguising itself by altering
its genetic code, thereby changing its antigen coating in resistance to
each new antibody that evolves. This ―quick change‖ has confounded
pathologists and made the development of effective vaccines elusive.

A controversy has been sparked between proponents of the
elimination of the tsetse fly and African environmentalists. Those in
favour of eradication feel that in addition to reducing disease, the
removal of the tsetse fly will open immense tracts of land to cattle
breeding. This, however, is precisely what the opposition fears.
Environmentalists and conservationists dread the day when cattle and
livestock, permitted to roam and graze freely, will uncontrollably devour
plush African grasslands, converting them into barren desert. They argue
that the tsetse fly must remain for the sake of the land.

With efforts to eradicate the tsetse fly largely unsuccessful, control
may offer the only available option for the interests of both health and
environment. Since the protozoan cannot be conquered through
antibodies or vaccines, scientists have begun efforts to prevent the
transmission of the trypanosome parasite by eliminating the tsetse.
Attempts to eradicate the tsetse fly, however, have met with little
success. Rhodesia used to combat tsetse by extensive brush cleaning,
game shooting, and chemical attack, yet the fly persisted. Aerial pesticide
treatments have produced inconclusive results.

The reproductive cycle of the tsetse fly is such that a larva pupates
underground for several weeks before it emerges as an adult fly. This
makes repetitive chemical sweeping at intermittent periods an
inconvenient necessity. All of these methods, however, share the
weakness of dependence on harmful chemicals, such as DDT, which
threaten both the health of the humans who handle them and the
environment in which their toxic residues amass.

1. All of the following statements correctly describe the relationship between
the tsetse fly, the trypanosome, and vertebrates EXCEPT:

A. vertebrate blood provides the nourishment for the transport of
trypanosomes.
B. the ―bite‖ of a tsetse fly can kill vertebrates since it often injects a
deadly chemical.
C. both the tsetse fly and the trypanosome utilize vertebrate blood for
nourishment.
D. vertebrates may die after trypanosome contamination via a tsetse
proboscis.
E. the tse tse fly transfers the trypanosome into the vertebrates' bodies

2. In the passage, the author does NOT identify which of the following as a
characteristic of the tsetse fly?

A. dependence upon vertebrate blood
B. ability to transmit a fatal parasite to livestock and humans
C. ability to alter its genetic code
D. ability to influence the African cattle population
E. its larva pupates for several weeks beneath the ground

3. According to African environmentalists, which of the following accurately
describes the effect the tsetse fly has on the African grasslands?

A. If the tsetse fly population continues to exist, the African grasslands
will turn into barren wasteland.
B. If the tsetse fly population continues to exist, the African grasslands
will not be able to provide sufficient food supply for African cattle and
livestock.
C. Destruction of the tsetse fly population will lead to the conversion of
grasslands into desert.
D. Destruction of the tsetse fly population will cause overgrowth of the
African grasslands.
E. Tse tse fly has no impact on grasslands, it only impacts vertebrates

4. What is the primary purpose of the fourth paragraph in the passage

A. to decsribe the harmful effects of the tse tse fly
B. to argue that the proliferation of tse tse flies can lead to large scale
deforestation of African grasslands
C. to discuss a beneficial impact of tse tse flies
D. to state that efforts to eradicate the tse tse flies have generally proved
to be ineffective
E. to discuss the reproductive cycle of a tse tse fly

Last edited by anilnandyala on 20 Nov 2010, 20:00, edited 1 time in total.
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Re: rc 99, tsetse fly science passage [#permalink] New post 20 Nov 2010, 19:58
answers will be provided after a discussion, proviode ur answers with explanations.
1 q answer c because only tsetse uses blood for nourishment not trpyansome
2 c ability to alter its genetic code is answer because from passage 3 trypansome is capable of changing it's genetic code not insect
3 c Destruction of the tsetse fly population will lead to the conversion of
grasslands into desert, an easy one the environmenatalists opposes destroying tsetse because cattle will sweep entire green land in the absence of tsetse
4 c to discuss a beneficial impact of tse tse flies, direct q here the passage offers advantages of tsetse
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Re: rc 99, tsetse fly science passage [#permalink] New post 21 Nov 2010, 01:51
1:B
2:C
3:C
4:D
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Re: rc 99, tsetse fly science passage [#permalink] New post 21 Nov 2010, 20:59
Here are my answers:
1. E
2. C
3. C
4. D
What are the OAs?
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Re: rc 99, tsetse fly science passage [#permalink] New post 22 Nov 2010, 05:31
oa's are bccc
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Re: rc 99, tsetse fly science passage [#permalink] New post 23 Nov 2010, 09:48
Got 3/4 , for last one it was my careless mistake did not count the paragraphs :-(..hope to avoid such silly mistakes on real GMAT
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Re: rc 99, tsetse fly science passage [#permalink] New post 30 Apr 2011, 11:06
Friends Will you provide me the electronic version of RC-99.... I believe that will be helpfull for me.
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Re: rc 99, tsetse fly science passage [#permalink] New post 06 May 2011, 03:36
3/4 in exactly 7:00 min. although i dont agree with answer for the 3rd question . i think it has to be E , because tsotsobe fly has no impact on grasslands, it does not suck the blood out of grass. the fly does not eat the grass either, it only sucks the blood of vertebrates.

and option E exclusively states just that.
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Re: rc 99, tsetse fly science passage [#permalink] New post 06 May 2011, 03:41
option C in q 3 clearly states that elimination of tsotsobe fly WILL lead to conversion of grasslands into deserts . this is a clear exaggeration.

anyone to counter this ?
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Re: rc 99, tsetse fly science passage [#permalink] New post 06 May 2011, 04:25
garimavyas wrote:
option C in q 3 clearly states that elimination of tsotsobe fly WILL lead to conversion of grasslands into deserts . this is a clear exaggeration.

anyone to counter this ?


Question states: "According to African environmentalists".

"C" would be an exaggeration if the Author, not the African environmentalists, were to conclude something based on the premise. Here, the word "will" is used to describe African environmentalists' exact thinking, which is of course an adamant hypothesis, about the effect on grassland upon eradication of tsetse flies.


Environmentalists and conservationists dread the day when cattle and
livestock, permitted to roam and graze freely, will uncontrollably devour
plush African grasslands, converting them into barren desert.
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Re: rc 99, tsetse fly science passage [#permalink] New post 13 May 2011, 11:31
4/4 in 8 minutes... long passage.

1. B, D and B somewhat contradict IMO and I liked D better. Passage didn't talk about bite or chemical.
2. C, trypanosome alters code, not the teste fly.
3. C, Less teste's -> more cattle -> less grass -> desert
4. C, Explains the answer in question 3.
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Re: rc 99, tsetse fly science passage [#permalink] New post 01 Aug 2011, 20:50
7:50.

I got

B
C
E
C.

How come the 3rd is C? I was down to C and E. But chose E because the fly has no direct impact on the grassland. The fly impacts the grassland indirectly by keeping the population of animals in check.

PS: fluke's explanation makes sense.
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Re: rc 99, tsetse fly science passage   [#permalink] 01 Aug 2011, 20:50
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