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结论解释型
Species interdependence（ interdependencen.互相依赖）in nature confers many benefits on the species involved, but it can also become a point of weakness when one species involved in the relationship is affected by a catastrophe. Thus, flowering plant species dependent on insect pollination, as opposed to self-pollination or wind pollination, 对比点could be endangered when the population of insect-pollinators is depleted by the use of pesticides.种群互相依赖不好。所以，虫媒花易受害（虫媒花与风媒花对比）
In the forests of New Brunswick, for example, various pesticides have been sprayed in the past 25 years in efforts to control the spruce budworm, an economically significant pest. Scientists have now investigated the effects of the spraying of Matacil, one of the anti-budworm agents that is least toxic to insect-pollinators. They studied Matacil’s effects on insect mortality in a wide variety of wild insect species and on plant fecundity, expressed as the percentage of the total flowers on an individual plant that actually developed fruit and bore seeds. They found that the most pronounced mortality after the spraying of Matacil occurred among the smaller bees and one family of flies, insects that were all important pollinators of numerous species of plants growing beneath the tree canopy of forests. The fecundity of plants in one common indigenous species, the red-osier dogwood, was significantly reduced in the sprayed areas as compared to that of plants in control plots where Matacil was not sprayed. This species is highly dependent on the insect-pollinators most vulnerable to Matacil. 对比点The creeping dogwood, a species similar to the red-osier dogwood, but which is pollinated by large bees, such as bumblebees, showed no significant decline in fecundity. Since large bees are not affected by the spraying of Matacil, 结论：these results add weight to the argument that spraying where the pollinators are sensitive to the pesticide used decreases plant fecundity.以NB为例，说明虫媒花易受影响。喷M对植物结果的影响。实验情况：RD受影响，CD不受影响。（对比点）结论：对喷对农药敏感的花会受影响。
The question of whether the decrease in plant fecundity caused by the spraying of pesticides actually causes a decline in the overall population of flowering plant species still remains unanswered. 对比点Plant species dependent solely on seeds for survival or dispersal are obviously more vulnerable to any decrease in plant fecundity that occurs, whatever its cause. If, on the other hand, vegetative growth and dispersal (by means of shoots or runners) are available as alternative reproductive strategies for a species, then decreases in plant fecundity may be of little consequence. The fecundity effects described here are likely to have the most profound impact on plant species with all four of the following characteristics:列举（4个）a short life span, a narrow geographic range, an incapacity for vegetative propagation, and a dependence on a small number of insect-pollinator species. 建议：Perhaps we should give special attention to the conservation of such plant species since they lack key factors in their defenses against the environmental disruption caused by pesticide use.是否会对整个种群有影响：未知。 对比点：seed/shoot or runner , 易受影响的四个特点。提出建议：保护植物
1. Which of the following best summarizes the main point of the passage?主题题
(A) Species interdependence is a point of weakness for some plants, but is generally beneficial to insects involved in pollination.
(B) Efforts to control the spruce budworm have had deleterious effects on the red-osier dogwood.太具体了
(C) The used of pesticides may be endangering certain plant species dependent on insects for pollination.
(D) The spraying of pesticides can reduce the fecundity of a plant species, but probably does not affect its overall population stability.（C）
(E) Plant species lacking key factors in their defenses against human environmental disruption will probably become extinct.
这题我做错了选了D D为何不对呢 D分别是第二段和第三段的中心句
5. It can be inferred that which of the following is true of plant fecundity as it is defined in the passage?我选了E
(A) A plant’s fecundity decreases as the percentage of unpollinated flowers on the plant increases.
plant fecundity, expressed as the percentage of the total flowers on an individual plant that actually developed fruit and bore seeds.
(B) A plant’s fecundity decreases as the number of flowers produced by the plant decreases.
(C) A plant’s fecundity increases as the number of flowers produced by the plant increases.
(D) A plant’s fecundity is usually low if the plant relies on a small number of insect species for pollination.（A）
(E) A plant’s fecundity is high if the plant can reproduce quickly by means of vegetative growth as well as by the production of seeds.
这题的答案是不是错了应该是E吧
plant fecundity, expressed as the percentage of the total flowers on an individual plant that actually developed fruit and bore seeds.
谢谢
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发表于 2004-4-21 12:03:00
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