[1] Ranging from viruses to humans, genes from virtually all kinds of organisms can now be inserted into plants, creating what are known as transgenic plants. Now used in agriculture, there are approximately 109 million acres of transgenic crops grown worldwide, 68 percent of which are in the United States. The most common transgenic crops are soybeans, corn, cotton, and canola. More often than not, these plants will contain a gene that either makes them resistant to the herbicide glyphosate or produces an insect-resistant protein called Bt toxin.
[2] Advocates
of transgenic crops argue that the benefit of these crops is that they’re
environmentally friendly, allowing farmers to use smaller amounts of less
noxious chemicals for crop production. For example, there has been a 21 percent
reduction in the use of insecticide reported on Bt cotton (transgenic cotton
that produces Bt toxin). In addition, when glyphosate is used to control weeds,
other more persistent herbicides do not need to be
applied.
[3] However,
adversaries of transgenic crops suggest that there are still many unanswered
questions that must be addressed before transgenic crops will be safe to grow
on a larger scale. Some questions concern the effects that Bt plants have on
non-target organisms, such as beneficial insects, worms, and birds that consume
the genetically engineered crop. For example, monarch caterpillars feeding on
milkweed plants near Bt cornfields feed on corn pollen that has fallen on the
milkweed leaves. Laboratory studies indicate that caterpillars can die from
eating Bt pollen. However, field tests indicate that Bt corn is not likely to
harm monarchs. Furthermore, the application of pesticides (the alternative to
growing Bt plants) has been demonstrated to cause widespread harm to non-target
insects.
[4] Another
question that remains unanswered is whether herbicide-resistant genes will move
into the various populations of weeds. Crop plants are sometimes grown in areas
where weedy relatives also live. If the crop plants crossbreed and reproduce
with weedy relatives, then this herbicide-resistant gene will be perpetuated in
the offspring. In this way, the resistant gene can make its way into the weed
population. If this happens, a farmer can no longer use glyphosate, for
example, to kill those weeds. This scenario is not
likely to occur in many instances when there are no weedy relatives growing
near the crop plant. However, in some cases, it may become a serious problem.
For example, canola readily hybridizes with mustard weed species and could
transfer its herbicide-resistant genes to those weeds. We know that evolution
will occur when transgenic plants are grown on a large scale over a period of
time. The development of insect populations resistant to the Bt toxin is of
particular concern. This pesticide has already been applied to plants for
decades without the development of insect-resistant populations. However,
transgenic Bt plants express the toxin in all tissues throughout the growing
season. Therefore, all insects carrying genes that make them susceptible to the
toxin will die. Such an event would leave only the genetically resistant
insects alive to perpetuate the population. When these resistant insects mate,
they will produce a high proportion of offspring capable of surviving in the
presence of the Bt toxin. Farmers are using different methods in an attempt to
slow the development of insect resistance in Bt crops. For example, some
farmers are planting nontransgenic border rows to provide refuge for
susceptible insects. These insects may allow Bt susceptibility to remain in the
population.
[5] Perhaps
the most serious concern about the transgenic crop plants currently in use is
that they encourage farmers to move farther away from sustainable agricultural
farming practices, meaning ones that allow natural resources to continually
regenerate over the long run. Transgenic plants, at least superficially,
simplify farming by reducing the choices made by the manager. Planting a
glyphosate-resistant crop commits a farmer to use that herbicide for the
season, probably to the exclusion of all other herbicides and other
weed-control practices. Farmers who use Bt transgenic may not feel that they
need to follow through with integrated pest-management practices that use
beneficial insects and timely applications of pesticides to control insect
pests. A more sustainable approach would be to plant non-transgenic corn,
monitor the fields throughout the growing season, and then apply a pesticide
only if and when needed.
1 According
to paragraph 2, supporters claim that producing transgenic plants enables
farmers to
- control weeds without the use of
chemicals
- take advantage of more effective
pesticides
- use fewer and less toxic chemicals
- increase harvesting up to 21
percent
ANSWER
EXPLANATION
Question is
worth: 1 point.
Correct Answer:
c
Your Selection: Not Answered
The correct
answer is (C): use fewer and less toxic chemicals.
A is incorrect as the use of transgenic methods is not for weed control. Weeds
are not mentioned in paragraph 2.
B is incorrect as it prevents the use of strong pesticides by making plants
more pest resistant.
D is incorrect as an increased harvest is not mentioned.
2 Which of
the following can be inferred about monarch caterpillars from paragraph 3?
- They are considered beneficial
insects.
- They are the species most resistant
to herbicides.
- There is little to no existing
research available concerning their behavior.
- They regularly cause harm to all
kinds of crops.
ANSWER
EXPLANATION
Question is
worth: 1 point.
Correct Answer:
a
Your Selection: Not Answered
The correct
answer is A: They are beneficial insects. The author lists the types of
beneficial insects, and other animals, which might be negatively affected by
transgenic plants, and then uses Monarchs as an example to illustrate the
point.
B is incorrect as the text states that they might potentially negatively
affected by eating Bt pollen, but that they are definitely negatively affected
by pesticides. Herbicides are not mentioned in relation to Monarchs.
C is incorrect as the text refers to field research studies. The behavior of
these insects is not relevant to this research in any case, but rather the potential
for harm by Bt crops.
D is incorrect as the harm caused to crops by the caterpillars is not mentioned
in paragraph 3.
3 What
conclusion does the author make in passage 3 about the impact of Bt plants on
nontarget living beings?
- Bt plants have been shown in field
studies to cause great harm to micro-organisms.
- Bt plants do not cause as much harm
to non-target species as the use of conventional pesticides.
- Bt toxins don't influence
non-target organisms who consume transgenic plants at all.
- Even if Bt poisons don't influence
insects that feed on the plants, they effectively affect birds and human
beings.
ANSWER
EXPLANATION
Question is
worth: 1 point.
Correct Answer:
b
Your Selection: Not Answered
The correct
answer is B. The author explains, using the example of the Monarch, that
although there was thought to be some risk to insects by Bt plants, this has
been shown to be less harmful than conventional pesticides.
A is incorrect. The effects on microorganisms are not mentioned.
C is incorrect. The question as to whether Bt plans affect non-target insects
and other animals remains unanswered. Although the effect on Monarch’s, the
example cited, was found to be negligible, or not-harmful, this is only one
example. The argument of the adversaries remains a question.
D is incorrect. Negative effects are not concluded absolutely in paragraph 3.
4 Why does
the author mention “mustard weed species” in the discussion of plants that
hybridize?
- To give an example of a weed that
may become resistant to glyphosate due to hybridizing with a transgenic
plant
- To argue that creating transgenic
plants in the laboratory is not always necessary, as some can be created
through hybridizing in the fields
- To give evidence that related types
of plants are unaffected by transgenic plants
- To support the claim that it is
difficult to decide if a harvest plant has been planted far enough away
from any weeds
ANSWER
EXPLANATION
Question is
worth: 1 point.
Correct Answer:
a
Your Selection: Not Answered
The correct
answer is A: To give an example of a weed that may become resistant to
glyphosate due to hybridizing with a transgenic plant. This is clear in the
paragraph as the process of how glyphosate resistant weeds can develop.
B is incorrect as the paragraph focuses on weeds and how they hybridize with
transgenic plants.
C is incorrect as the author does not mention plants which would be unaffected
by transgenic plants. Instead it focuses on plants which might be affected,
particularly, weeds.
D is incorrect. The claim that planting crops sufficiently far away from any
weeds is to prevent the hybridization of transgenic plants with weeds, but the
paragraph does not pertain to deciding what distance is sufficient.
5 Paragraph
4 makes all of the following claims about Bt resistance in insect populations
EXCEPT
- Because Bt plants are toxic in all
tissues, they allow no insects that are susceptible to survive and
reproduce.
- The evolution of Bt-resistant
insect populations will happen eventually if the use of transgenic plants
becomes widespread.
- Planting no transgenic plants
alongside Bt plants may help Bt-susceptible insects to remain part of the
population.
- Regular use of Bt pesticides has
not created resistant insect populations, so the use of Bt plants is
probably safe as well.
ANSWER
EXPLANATION
Question is
worth: 1 point.
Correct Answer:
d
Your Selection: Not Answered
The correct
answer is D: regular use of Bt pesticides has not created resistant insect
populations, so the use of Bt plants is probably safe as well. This claim is not
made in paragraph 4, as paragraph 4 deals mainly with the potential for the
evolution of hybridized plants, the resultant resistant weeds, and the
evolution of resistant insects.
A is incorrect as claim that insects susceptible to the BT toxins will die is
true and made in paragraph 4.
B is incorrect as this claim is made in paragraph 4 as follows: “However,
transgenic Bt plants express the toxin in all tissues throughout the growing
season. Therefore, all insects carrying genes that make them susceptible to the
toxin will die. Such an event would leave only the genetically resistant
insects alive to perpetuate the population”.
C is incorrect as this claim is made in paragraph 4. “Farmers are using
different methods in an attempt to slow the development of insect resistance to
Bt crops. For example, some farmers are planting nontransgenic border rows to
provide a refuge for susceptible insects. These insects may allow Bt
susceptibility to remain in the population”.
6 Which of
the following best expresses the essential information in the highlighted
sentence? Incorrect answer choices change the meaning in important ways or
leave out essential information.
Perhaps the
most serious concern about the transgenic crop plants currently in use is that
they encourage farmers to move farther away from sustainable agricultural
farming practices, meaning ones that allow natural resources to continually
regenerate over the long run.
- The transgenic crop plants
currently in use are behind the transgenic plants of the future in terms
of their sustainability.
- Transgenic plants grown as crops
may be used in place of other, more sustainable agricultural practices,
and this is perhaps their biggest disadvantage.
- Farmers who use transgenic crop
plants are heading towards good growing habits which will result in a
surplus amount of crops.
- The most serious concern about the
transgenic crop plants currently in use is the possibility that they may
not be sustainable over the long run.
ANSWER
EXPLANATION
Question is
worth: 1 point.
Correct Answer:
d
Your Selection: Not Answered
D is the
correct answer because it keeps the focus on the concern of using transgenic
plants and how they may be unsustainable.
A is incorrect as the evolutionary conditions of transgenic plants are the same
for present and future versions of Bt crops. Transgenic methods are
unsustainable in general.
B is incorrect because its focus is on being able to replace more sustainable
practices with transgenic plants, while the highlighted sentence focuses on the
concern of using transgenic plants.
C is incorrect as the point of this example sentence is the negative effects of
transgenic plants and practices. ‘Good growing habits’ are not a characteristic
of transgenic plants according to the example sentence.
7 According
to paragraph 5, a sustainable approach to weed and pest control includes all of
the following EXCEPT
- Planting non-transgenic crops
- Applying pesticides only when
needed
- Keeping a close eye on the crops
- Using multiple types of herbicide throughout
the growing season
ANSWER
EXPLANATION
Question is
worth: 1 point.
Correct Answer:
d
Your Selection: Not Answered
The correct
answer is D, as this is the only claim not made in paragraph 5 about
sustainable practices.
A is incorrect as this claim is made in paragraph 5. Planting non-transgenic
crops is a more sustainable farming practice.
B is incorrect as the paragraph is about the careful management of the use of
pesticides, and reference is made to ‘timely applications’.
C is incorrect as this statement is true. “Transgenic plants, at least
superficially, simplify farming by reducing the choices made by the manager”.
This statement shows that the managers who use Bt crops are less inclined to
focus carefully on sustainable growing practices, and care.
8 The word
'superficially' in paragraph 5 is closest in meaning to:
- when done incorrectly
- right now
- on the surface
- with deeper analysis
ANSWER
EXPLANATION
Question is
worth: 1 point.
Correct Answer:
c
Your Selection: Not Answered
The correct
answer is C: On the surface.
Superficially is defined as ‘on the surface’, or ‘not thoroughly or deeply’.
A, B and C are incorrect as these are not synonymous with superficial.
9 Examine
the four █ in the selection below and indicate at which block the following
sentence could be inserted into the passage:
It is especially rare in the United States, where most transgenic plants are
grown, because most of the crops grown in the United States originated
elsewhere.
If the crop
plants crossbreed and reproduce with weedy relatives, then this
herbicide-resistant gene will be perpetuated in the offspring. █
[A] In this way, the resistant gene can make its way into the weed
population. █ [B] If this happens, a farmer can no longer use
glyphosate, for example, to kill those weeds. █ [C] This scenario is
not likely to occur in many instances because there are no weedy relatives
growing near the crop plant. █ [D] However, in some cases, it may
become a serious problem. For example, canola readily hybridizes with mustard
weed species and could transfer its herbicide-resistant genes to those weeds..
- [A]
- [B]
- [C]
- [D]
ANSWER
EXPLANATION
Question is
worth: 1 point.
Correct Answer:
d
Your Selection: Not Answered
The correct
answer is D. The sentence preceding position D mentions the low likelihood of
occurrence, which is then emphasized in the example sentence with the use of
‘especially rare’. The following sentence, beginning with ‘However’ completes
the logic of the argument made. The paragraph will then read as follows:
This scenario is not likely to occur in many instances because there are no
weedy relatives growing near the crop plant. It is especially rare in the
United States, where most transgenic plants are grown because most of the crops
grown in the United States originated elsewhere. However, in some cases, it may
become a serious problem. For example, canola readily hybridizes with mustard
weed species and could transfer its herbicide-resistant genes to those weeds.
A is incorrect as the sentences before and after position A follow logically.
The joining phrase ‘in this way’ makes the juxtaposition of these necessary and
correct.
B is incorrect as the phrase ‘If this happens’ refers logically to how the
resistant gene can make its way into the weed population.
C is incorrect as the opening phrase of the sentence following C, ‘This
scenario” refers to how farmers can no longer use glyphosate.
10Directions: An
introductory sentence for a brief summary of the passage is provided below.
Complete the summary by selecting the THREE answer choices that express the
most important ideas in the passage. Some sentences do not belong in the
summary because they express ideas that are not presented in the passage or are
minor ideas in the passage. This question is worth 2 points.
Drag your
answer choices to the spaces where they belong. To remove an answer choice,
drag it back. To review the passage, click VIEW TEXT.
Transgenic
plants include genes from other organisms that make them resistant to
glyphosate or toxic to insects.
- A.Opponents of transgenic plants
worry that resistance to glyphosate may spread to weeds and that
resistance to Bt toxin may develop among insect pests.
- B.Use of transgenic plants may lead
farmers to neglect more sustainable agricultural practices, and may also
cause harm to non-target organisms.
- E. Although transgenic plants are
useful in some areas, they are not particularly useful in place of
pesticides.
- A.Opponents of transgenic plants
worry that resistance to glyphosate may spread to weeds and that
resistance to Bt toxin may develop among insect pests.
- B.Use of transgenic plants may lead
farmers to neglect more sustainable agricultural practices, and may also
cause harm to non-target organisms.
- C.One argument against Bt plants is
that some of the most harmful pests are not Bt-susceptible, making
application of supplementary pesticides necessary.
- D.Over the long term, transgenic
plants are likely to lose their glyphosate resistance through evolution
and hybridization with non-resistant relatives.
- E. Although transgenic plants are
useful in some areas, they are not particularly useful in place of
pesticides.
- F. Proponents of transgenic plants
argue that they reduce the use of harmful pesticides and allow the use of
more environmentally friendly herbicides.
ANSWER
EXPLANATION
Question is
worth: 2 points.
Correct Answer:
a,b,e
Your Selection: Not Answered
The correct
answer is A, B, E
These sentences in this order capture the salient points of the text.
The summary paragraph will then read as follows:
Opponents of transgenic plants worry that resistance to glyphosate may spread
to weeds and that resistance to Bt toxin may develop among insect pests.
Use of transgenic plants may lead farmers to neglect more sustainable
agricultural practices and may also cause harm to non-target organisms.
Although transgenic plants are useful in some areas, they are not particularly
useful in place of pesticides.
C is incorrect as this claim is not made in the narrative, and undermines the
complexity of the trade-off between the use of Bt crops, and more sustainable
practices.
D is incorrect as glyphosate resistance is potentially a very real outcome of
the use of Bt practices.
F is incorrect as herbicides in relation to transgenic plants are not mentioned
in the text.
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