GMAT考试阅读试题(四)(3)Passage 20Species interdependence in nature confers manybenefits on the species involved， but it can also become apoint of weakness when one species involved in the rela-tionship is affected by a catastrophe. Thus， flowering（5） plant species dependent on insect pollination， as opposedto self-pollination or wind pollination， could be endan-gered when the population of insect-pollinators is depletedby the use of pesticides.In the forests of New Brunswick， for example，（10） various pesticides have been sprayed in the past 25 yearsin efforts to control the spruce budworm， an economi-cally significant pest. Scientists have now investigatedthe effects of the spraying of Matacil， one of the anti-budworm agents that is least toxic to insect-pollinators.（15） They studied Matacils effects on insect mortality in awide variety of wild insect species and on plant fecun-dity， expressed as the percentage of the total flowers onan individual plant that actually developed fruit andbore seeds. They found that the most pronounced（20） mortality after the spraying of Matacil occurred amongthe smaller bees and one family of flies， insects that wereall important pollinators of numerous species of plantsgrowing beneath the tree canopy of forests. The fecun-dity of plants in one common indigenous species， the（25） red-osier dogwood， was significantly reduced in thesprayed areas as compared to that of plants in controlplots where Matacil was not sprayed. This species ishighly dependent on the insect-pollinators most vulner-able to Matacil. The creeping dogwood， a species similar（30） to the red-osier dogwood， but which is pollinated bylarge bees， such as bumblebees， showed no significantdecline in fecundity. Since large bees are not affected bythe spraying of Matacil. these results and weight to theargument that spraying where the pollinators are sensi-（35） tive to the pesticide used decreases plant fecundity.The question of whether the decrease in plant fecun-dity caused by the spraying of pesticides actually causesa decline in the overall population of flowering plantspecies still remains unanswered. Plant species dependent（40） solely on seeds for survival or dispersal are obviouslymore vulnerable to any decrease in plant fecundity thatoccurs， whatever its cause. If， on the other hand， vegeta-tive growth and dispersal （by means of shoots or runners）are available as alternative reproductive strategies for a（45） species， then decreases in plant fecundity may be of littleconsequence. The fecundity effects described here arelikely to have the most profound impact on plant specieswith all four of the following characteristics： a short lifespan， a narrow geographic range， an incapacity for vege-（50） tative propagation， and a dependence on a small numberof insect-pollinator species. Perhaps we should give specialattention to the conservation of such plant species sincethey lack key factors in their defenses against the envi-ronmental disruption caused by pesticide use. 1. Which of the following best summarizes the main pointof the passage？ （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.（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.（E） Plant species lacking key factors in their defenses against human environmental disruption will probably become extinct. 2. According to the author， a flowering plant species whosefecundity has declined due to pesticide spraying maynot experience an overall population decline if the plantspecies can do which of the following？ （A） Reproduce itself by means of shoots and runners.（B） Survive to the end of the growing season.（C） Survive in harsh climates.（D） Respond to the fecundity decline by producing more flowers.（E） Attract large insects as pollinators 3. The passage suggests that the lack of an observed decline in the fecundity of the creeping dogwood strengthens the researchers conclusions regarding pesticide use because the （A） creeping dogwood its a species that does not resemble other forest plants（B） creeping dogwood is a species pollinated by a broader range of insect species than are most dogwood species（C） creeping dogwood grows primarily in regions that were not sprayed with pesticide， and so served as a control for the experiment（D） creeping dogwood is similar to the red-osier dogwood， but its insect pollinators are known to be insensitive to the pesticide used in the study（E） geographical range of the creeping dogwood is similar to that of