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Pesticides (including insecticides, fungicides, nematicides, and herbi

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Concentration: Finance
GPA: 2.77
WE: General Management (Other)
Pesticides (including insecticides, fungicides, nematicides, and herbi  [#permalink]

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New post 26 Oct 2018, 01:02
Question 1
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based on 15 sessions

20% (01:09) correct 80% (03:05) wrong

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Question 2
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based on 15 sessions

13% (00:44) correct 87% (00:33) wrong

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Question 3
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based on 14 sessions

36% (00:53) correct 64% (01:25) wrong

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Pesticides (including insecticides, fungicides, nematicides, and herbicides) are chemicals used in agriculture to increase production by combating organisms that damage or destroy plants. However, pesticides by their very nature can result in serious harm to wildlife both by directly killing animals and through more subtle effects on reproduction, development and behaviour. Organophosphates are pesticides that interfere with the enzyme cholinesterase, which is essential for the proper functioning of the nervous systems of insects, as well as of humans and other vertebrates. Toxic exposure to organophosphates results in fatal respiratory failure. The first indicator of toxic absorption is a reduction in the enzyme cholinesterase in red blood cells, and contact with insecticides is the only known cause of a marked depression of this enzyme.

In a recent study, researchers collected specimens of both adult and tadpole Pacific treefrogs from sites located both within the Sierra Nevada (representing northern and southern areas) and also to its west (representing the foothills and the Pacific coast of California). When cholinesterase levels were then examined they were significantly lower in tadpoles taken from the mountains east of the San Joaquin Valley, such as Yosemite and Sequoia National Parks, than in those taken from similar sites farther north in the Sierra Nevada, which lie east of the Sacramento Valley where agricultural activity is less intense.

Moreover, lower cholinesterase activity levels were correlated with distance away from the coast and toward the higher elevations of the Sierra Nevada. Similar, although less significant, trends were seen in adult frogs. Concentrations of particular organophosphate pesticides in the collected tadpoles and adult frogs were also measured. More than fifty percent of the adult frogs and tadpoles at Yosemite National Park had measurable levels of diazinon and chlorpyrifos, compared to only nine percent at coastal sites. Since both diazinon and chlorpyrifos degrade very rapidly in organisms, the detection of either compound indicates recent exposure to the chemicals. The red-legged frog is now listed as threatened under the U.S. Endangered Species Act, and the mountain yellow-legged frog and Yosemite toad have been proposed for listing. Many amphibian population declines have occurred in some of the state's most seemingly pristine areas, such as the Sierra Nevada mountain range of eastern California which includes Sequoia, Yosemite, Kings Canyon, and Lassen Volcanic National Parks as well as Lake Tahoe and Mt. Whitney.

Because the southern parts of the Sierra Nevada lie east of the intensely agricultural San Joaquin Valley, environmentalists have suspected that pesticide use may be responsible. Pesticides could be transported from the San Joaquin Valley to the Sierra Nevada on the prevailing eastward summer winds, and then affect populations of amphibians that breed in mountain ponds and streams.
1. In the passage, the author most likely mentions that population declines have occurred in seemingly pristine areas (line 36) in order to emphasize that:
A. while there has been some damage to the environment of the Sierra Nevada, it is not irreparable.
B. appropriate action should be taken to restore the Sierra Nevada to its former purity.
C. environmental damage and its causes may not be apparent to casual observers.
D. because some amphibian species are still abundant in the Sierra Nevada, casual observers do not realize how many are seriously threatened.
E. the environmental damage caused by pesticides has been all pervasive

2. With respect to pesticides, the author takes time in the passage to assert that they:
A. are transported for long distances by wind currents.
B. are detrimental to both insects and vertebrates.
C. are not used in the Sierra Nevada.
D. have benefits in agricultural applications.
E. should be absolutely banned

3. The function of the third paragraph in relation to the passage as a whole is to:
A. critique the scientific study alluded to in the first paragraph.
B. present evidence to support a hypothesis introduced in the first paragraph.
C. provide more details with respect to the geographical information introduced in the first paragraph.
D. provide more specific examples of the harmful effects of pesticides mentioned in the second paragraph.
E. present data to undermine a theory introduced in the first paragraph.


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Re: Pesticides (including insecticides, fungicides, nematicides, and herbi  [#permalink]

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New post 26 Oct 2018, 01:05

Topic and Scope

- Pesticides and the decline of California amphibian populations

Mapping the Passage


¶1 describes the mechanism of pesticide toxicity for the enzyme cholinesterase.
¶s2 and 3 describe experimental evidence suggesting that pesticides negatively affect amphibian species and describe the decline in amphibian populations in various areas of California.
¶4 suggests a mechanism by which pesticides would be transported through wind to contaminate the Sierra Nevada.

Strategy Point:
Be sure to understand cause-and-effect relationships in Natural Science passages. A simple flowchart that diagrams what the passage says can be an effective form of mapping.
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Senior Manager
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Re: Pesticides (including insecticides, fungicides, nematicides, and herbi  [#permalink]

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New post 26 Oct 2018, 01:06

Answers and Explanations OE


1)

Review the lines in context. Why would the author want to make a point about population declines in ―seemingly pristine‖ areas especially? Predict: Even though the areas seem pristine, they might not in fact be so if amphibian populations are declining; they might be contaminated by pesticides that simply aren‘t obvious. (C) says the same.
(A): Out of Scope. The author only discusses contamination; anything about repair is outside the author‘s topic, and wouldn‘t have anything to do with the specific mention of ―seemingly pristine‖ areas anyway.
(B): Out of Scope. As above, the author never discusses whether or how to fix the damage caused by pesticides.
(C): The correct answer
(D): Distortion. Casual observers might not realize that there‘s pollution, but the author never argues that amphibians are abundant
(E): This is not the idea as is clear from the above explanation

2)

A detail question. Where are pesticides primarily mentioned? Focus your search on ¶s 1 and 4. (D) follows directly from the author‘s point in the first sentence of ¶1: Pesticides are useful in attacking organisms that harm plants.
(A): Distortion. Though the author says that pesticides might be transported ―on the prevailing eastward summer winds,‖ there‘s no way to tell whether they‘re in fact transported a long distance.(B): Distortion. The author states in ¶1 that organophosphates are harmful to both insects and vertebrates, but doesn‘t assert this about pesticides in general, as the question requires.
(C): Out of Scope. While this sounds plausible, the author never discusses potential pesticide use in the Sierra Nevada, only contamination from pesticides used
elsewhere.
(D): The correct answer
(E): Opposite as well as Extreme

3)

An evaluation question; refer to your map. What is the author‘s purpose in writing the third paragraph? Predict: The author wants to describe a mechanism by which some pesticides can harm animal populations. The answer choices are abstract, so compare them to your prediction piece-by-piece. (B) holds up: The mechanism of action is evidence, and it supports the hypothesis in ¶3 that pesticides are in fact hurting the frog population.
(A): Out of Scope. While the author does allude to a scientific study in ¶3 by mentioning that amphibian populations are declining (someone had to study that), the author never critiques the study.
(B): The correct answer
(C): Out of Scope. The author doesn‘t discuss any geographic information in ¶1.
(D): Distortion. Though the author does provide examples of harmful effects in ¶1, there are no harmful pesticide effects mentioned in ¶2; there‘s only the suggestion of a link between pesticide use and amphibian population decline.
(E): Opposite as mentioned in ‗B‘ above

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Re: Pesticides (including insecticides, fungicides, nematicides, and herbi  [#permalink]

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New post 29 Oct 2018, 13:30
Most of the passage is about the level of cholinesterase and its impact on vertebrates. cholinesterase itself gets interfered by Organophosphates, which is a pesticide. So, I am wondering about your answer to second question. In my understanding the answer should be B --> "are detrimental to both insects and vertebrates"
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Re: Pesticides (including insecticides, fungicides, nematicides, and herbi &nbs [#permalink] 29 Oct 2018, 13:30
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Pesticides (including insecticides, fungicides, nematicides, and herbi

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