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Free MCAT Test Exam Braindumps (page: 9)

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The Russian wheat aphid, Diuraphis noxia, is a small green insect discovered in southern Russia around the turn of the century. Agricultural researchers are not quite sure, but they believe the Russian aphid adapted itself to wheat about ten thousand years ago, when the crop was first domesticated by man. What is not in doubt is the insect's destructiveness. Spread by both wind and human transport, the Russian aphid has destroyed wheat fields throughout Asia, Africa, and Latin America. Until a few years ago, the United States had been free of this pest. But in the spring of 1986, a swarm of Russian aphids crossed the Mexican border and settled a few hundred miles north, in central Texas. From there, it quickly spread to other Western states, destroying wheat fields all along its path. In fact, the level of destruction has been so great over the past five years that entomologists are calling the Russian aphid the greatest threat to American agriculture since the Hessian fly, Phytophaga destructor, was inadvertently brought to the colonies on ships by German mercenary troops during the Revolutionary War. A combination of several factors has made it particularly difficult to deal with the threat posed by this aphid. First, Russian aphids reproduce asexually at a phenomenal rate. This process, known as parthenogenesis, often results in as many as twenty generations of insects in a single year. Although most generations remain in a limited geographic area because they have no wings, a few generations are born with wings, allowing the insect to spread to new areas. Second, because wheat is a crop with a very low profit margin, most American farmers do not spray it with pesticides; it simply is not economical to do so. And since the Russian aphid has only recently entered the United States, it has no natural enemies among North American insects or animals. As a result, there have been no man-made or natural obstacles to the spread of the Russian aphid in the United States.
Agricultural researchers seeking to control the Russian aphid have looked to its place of origin for answers. In the Soviet Union, the Russian aphid has been kept in check by predators which have evolved alongside it over many thousands of years. One species of wasp seems to be particularly efficient at destroying the aphid. The pregnant females of the species search the Russian aphid's home, the interior of a wheat stalk, sting the aphid into paralysis, and then inject an egg into its body. When the egg hatches the wasp larva feeds off of the aphid, killing it in the process.
The introduction of predators like the wasp, coupled with the breeding of new strains of insect-resistant wheat, may substantially curb the destructiveness of the Russian aphid in the future. For the time being, however, American farmers are left to their own devices when it comes to protecting their wheat crops.
It can reasonably be inferred that the author of the passage is:

  1. a botanist with an interest in wheat production.
  2. an agriculturist with an interest in pest control.
  3. a pest exterminator with an interest in agriculture.
  4. an entomologist with an interest in asexual reproduction.

Answer(s): B

Explanation:

This is an application question about the passage's authorship. In order to answer a question about authorship, it is necessary to consider the passage as a whole, particularly its content and level of complexity. Two major themes are reflected in this passage: (1) Russian aphids have spread far and wide, causing serious damage to wheat fields in America and other countries and (2) methods for controlling the aphid's destructiveness are currently being investigated by agricultural researchers. Given that the focus is on an agricultural crop being plagued by a destructive pest, an agriculturist with an interest in pest control, choice (B), is most likely to have written this passage. A botanist with an interest in wheat production, choice (A), is not likely to have written this passage because, although the passage deals with wheat and briefly mentions the possibility of producing insect-resistant strains of wheat (in the last paragraph), the passage certainly doesn't focus on the botany of wheat production. As for choice (C), if a pest exterminator with an interest in agriculture had written this passage we would expect a much more technical and detailed discussion about the ridding of this pest and the use of pesticides (and perhaps other chemicals) as possible means of controlling the aphid. And, this passage is unlikely to have been written by an entomologist with an interest in asexual reproduction, choice (D).
Although an entomologist, or someone who studies insects, may be a likely author, the aphid's method of reproduction is a minor issue in this passage, confined to a couple of sentences in the first half of the third paragraph.



The Russian wheat aphid, Diuraphis noxia, is a small green insect discovered in southern Russia around the turn of the century. Agricultural researchers are not quite sure, but they believe the Russian aphid adapted itself to wheat about ten thousand years ago, when the crop was first domesticated by man. What is not in doubt is the insect's destructiveness. Spread by both wind and human transport, the Russian aphid has destroyed wheat fields throughout Asia, Africa, and Latin America. Until a few years ago, the United States had been free of this pest. But in the spring of 1986, a swarm of Russian aphids crossed the Mexican border and settled a few hundred miles north, in central Texas. From there, it quickly spread to other Western states, destroying wheat fields all along its path. In fact, the level of destruction has been so great over the past five years that entomologists are calling the Russian aphid the greatest threat to American agriculture since the Hessian fly, Phytophaga destructor, was inadvertently brought to the colonies on ships by German mercenary troops during the Revolutionary War. A combination of several factors has made it particularly difficult to deal with the threat posed by this aphid. First, Russian aphids reproduce asexually at a phenomenal rate. This process, known as parthenogenesis, often results in as many as twenty generations of insects in a single year. Although most generations remain in a limited geographic area because they have no wings, a few generations are born with wings, allowing the insect to spread to new areas. Second, because wheat is a crop with a very low profit margin, most American farmers do not spray it with pesticides; it simply is not economical to do so. And since the Russian aphid has only recently entered the United States, it has no natural enemies among North American insects or animals. As a result, there have been no man-made or natural obstacles to the spread of the Russian aphid in the United States.
Agricultural researchers seeking to control the Russian aphid have looked to its place of origin for answers. In the Soviet Union, the Russian aphid has been kept in check by predators which have evolved alongside it over many thousands of years. One species of wasp seems to be particularly efficient at destroying the aphid. The pregnant females of the species search the Russian aphid's home, the interior of a wheat stalk, sting the aphid into paralysis, and then inject an egg into its body. When the egg hatches the wasp larva feeds off of the aphid, killing it in the process.
The introduction of predators like the wasp, coupled with the breeding of new strains of insect-resistant wheat, may substantially curb the destructiveness of the Russian aphid in the future. For the time being, however, American farmers are left to their own devices when it comes to protecting their wheat crops.
The passage supplies information for answering all of the following questions EXCEPT:

  1. What measures were taken to combat the Hessian fly during the 18th century?
  2. Why does the Russian wheat aphid cause less damage in the Soviet Union than in other countries?
  3. Is it logical for American farmers to use pesticides in order to attempt to protect their wheat crops from the Russian aphid?
  4. What sorts of solutions have agricultural researchers investigated in their efforts to curb the destructiveness of the Russian wheat aphid?

Answer(s): A

Explanation:

This is another scattered detail question that requires the reader to search throughout the passage to determine which answer choice is not covered. In the last sentence of the second paragraph, it is discussed that the Hessian fly was a major menace to American agriculture at the time of the Revolutionary War, but nowhere in the passage is it stated what, if anything, was done to combat this menace, so choice (A) is not answered in the passage and is the correct answer to this question. The second sentence of the fourth paragraph indicates that the Russian wheat aphid has done less damage in the Soviet Union than in other areas because natural predators which have evolved with it over the centuries have kept it in check, so choice (B) is addressed and is incorrect. In the fifth sentence of the third paragraph, we are told that it is not economical for American farmers to spray pesticides on their wheat in an attempt to protect their crops from the Russian aphid, so choice (C), too, is answered in the passage and is an incorrect choice. And, finally, the fourth and fifth paragraphs discuss possible means for controlling the aphid, particularly the introduction of the aphid's natural enemies, such as the female wasp, into new ecosystems and the breeding of insect-resistant strains of wheat, so choice (D), like (B) and (C), is answered and is wrong.



The Russian wheat aphid, Diuraphis noxia, is a small green insect discovered in southern Russia around the turn of the century. Agricultural researchers are not quite sure, but they believe the Russian aphid adapted itself to wheat about ten thousand years ago, when the crop was first domesticated by man. What is not in doubt is the insect's destructiveness. Spread by both wind and human transport, the Russian aphid has destroyed wheat fields throughout Asia, Africa, and Latin America. Until a few years ago, the United States had been free of this pest. But in the spring of 1986, a swarm of Russian aphids crossed the Mexican border and settled a few hundred miles north, in central Texas. From there, it quickly spread to other Western states, destroying wheat fields all along its path. In fact, the level of destruction has been so great over the past five years that entomologists are calling the Russian aphid the greatest threat to American agriculture since the Hessian fly, Phytophaga destructor, was inadvertently brought to the colonies on ships by German mercenary troops during the Revolutionary War. A combination of several factors has made it particularly difficult to deal with the threat posed by this aphid. First, Russian aphids reproduce asexually at a phenomenal rate. This process, known as parthenogenesis, often results in as many as twenty generations of insects in a single year. Although most generations remain in a limited geographic area because they have no wings, a few generations are born with wings, allowing the insect to spread to new areas. Second, because wheat is a crop with a very low profit margin, most American farmers do not spray it with pesticides; it simply is not economical to do so. And since the Russian aphid has only recently entered the United States, it has no natural enemies among North American insects or animals. As a result, there have been no man-made or natural obstacles to the spread of the Russian aphid in the United States.
Agricultural researchers seeking to control the Russian aphid have looked to its place of origin for answers. In the Soviet Union, the Russian aphid has been kept in check by predators which have evolved alongside it over many thousands of years. One species of wasp seems to be particularly efficient at destroying the aphid. The pregnant females of the species search the Russian aphid's home, the interior of a wheat stalk, sting the aphid into paralysis, and then inject an egg into its body. When the egg hatches the wasp larva feeds off of the aphid, killing it in the process.
The introduction of predators like the wasp, coupled with the breeding of new strains of insect-resistant wheat, may substantially curb the destructiveness of the Russian aphid in the future. For the time being, however, American farmers are left to their own devices when it comes to protecting their wheat crops.
The author suggests the best way to control the Russian aphid population in the United States is to:

  1. devote less acreage to the production of wheat.
  2. spray wheat fields with large quantities of pesticides.
  3. transplant its natural enemies from the Soviet Union.
  4. disrupt its reproductive process by sterilizing females.

Answer(s): C

Explanation:

This is an inference question about the author's perspective on how to control the Russian aphid population in the United States. The last 2 paragraphs of the passage concern control of the aphid population. In the first sentence of the fifth paragraph, the author suggests that the introduction of the aphid's natural predators into the United States holds the possibility of controlling the aphid population in the future. In other words, the author thinks that transplanting the Russian aphid's natural enemies from the Soviet Union, choice (C), is a logical way of controlling the aphid population in the United States, so (C) is the correct answer to this question. Nowhere in the passage does the author state or suggest that reducing the acreage devoted to the production of wheat, choice (A), would control the aphid population in the United States, so (A) is wrong. Although some people might logically conclude that growing less wheat would lessen the aphid population in the long-run, but the author doesn't suggest this as a logical method of aphid control. The question stem asks for a suggestion of the author. As for spraying large quantities of pesticides on wheat fields, choice (B), the author indicates in the fifth sentence of the third paragraph that, for economic reasons, this is not a reasonable method of aphid control, so choice (B) is wrong. Finally, the author doesn't suggest that sterilizing female aphids is a logical way of controlling the aphid population in the United States, making choice (D) incorrect. In fact, in the first half of the third paragraph, the author makes a point of noting that aphids reproduce asexually at a phenomenal rate, so "sterilizing females" is not logical at all and certainly is not suggested by the author.



The Russian wheat aphid, Diuraphis noxia, is a small green insect discovered in southern Russia around the turn of the century. Agricultural researchers are not quite sure, but they believe the Russian aphid adapted itself to wheat about ten thousand years ago, when the crop was first domesticated by man. What is not in doubt is the insect's destructiveness. Spread by both wind and human transport, the Russian aphid has destroyed wheat fields throughout Asia, Africa, and Latin America. Until a few years ago, the United States had been free of this pest. But in the spring of 1986, a swarm of Russian aphids crossed the Mexican border and settled a few hundred miles north, in central Texas. From there, it quickly spread to other Western states, destroying wheat fields all along its path. In fact, the level of destruction has been so great over the past five years that entomologists are calling the Russian aphid the greatest threat to American agriculture since the Hessian fly, Phytophaga destructor, was inadvertently brought to the colonies on ships by German mercenary troops during the Revolutionary War. A combination of several factors has made it particularly difficult to deal with the threat posed by this aphid. First, Russian aphids reproduce asexually at a phenomenal rate. This process, known as parthenogenesis, often results in as many as twenty generations of insects in a single year. Although most generations remain in a limited geographic area because they have no wings, a few generations are born with wings, allowing the insect to spread to new areas. Second, because wheat is a crop with a very low profit margin, most American farmers do not spray it with pesticides; it simply is not economical to do so. And since the Russian aphid has only recently entered the United States, it has no natural enemies among North American insects or animals. As a result, there have been no man-made or natural obstacles to the spread of the Russian aphid in the United States.
Agricultural researchers seeking to control the Russian aphid have looked to its place of origin for answers. In the Soviet Union, the Russian aphid has been kept in check by predators which have evolved alongside it over many thousands of years. One species of wasp seems to be particularly efficient at destroying the aphid. The pregnant females of the species search the Russian aphid's home, the interior of a wheat stalk, sting the aphid into paralysis, and then inject an egg into its body. When the egg hatches the wasp larva feeds off of the aphid, killing it in the process.
The introduction of predators like the wasp, coupled with the breeding of new strains of insect-resistant wheat, may substantially curb the destructiveness of the Russian aphid in the future. For the time being, however, American farmers are left to their own devices when it comes to protecting their wheat crops.
According to the passage, the Russian wheat aphid and the Hessian fly are comparable with respect to:
I) the amount of destruction they have caused.
II). the means by which they reproduce.
III). the ways in which they entered the United States.

  1. I only
  2. II only
  3. I and II only
  4. I and III only

Answer(s): A

Explanation:

This is another detail question in Roman numeral format involving a comparison of the Russian wheat aphid and the Hessian fly. Since these insects are briefly compared in the second paragraph, most likely the information necessary to answer the question will be found there. In the last sentence of the second paragraph, we are told that entomologists consider the Russian aphid so destructive that they have called it the greatest threat to American agriculture since the Hessian fly was brought over by German mercenaries during the Revolutionary War. Based on this, it is certainly reasonable to conclude that Russian aphids and Hessian flies are comparable with respect to the amount of damage they have caused to crops. Option I, therefore, does complete this question stem correctly, and will be part of the answer. The second sentence of the third paragraph states that Russian aphids reproduce asexually, but nowhere are we told by what means the Hessian fly reproduces, so we have no basis for concluding that Russian aphids and Hessian flies are comparable with respect to the means by which they reproduce, option II). The second sentence of the second paragraph states that a swarm of Russian aphids flew across the United States-Mexican border; in other words, they entered the United States on their own, with humans having nothing to do with their entry into this country.
In contrast, the final sentence of the second paragraph clearly states that the Hessian fly was brought to the United States by humans, German mercenary troops, in boats. So, their methods of entry into the United States aren't comparable, making option III incorrect.






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