请教XDF补充第11篇(2772的63-20)

Passage 20 (20/63)

Species interdependence 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, could be endangered when the population of insect-pollinators is depleted by the use of pesticides.

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 (distinct, obvious) 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(aboriginal, native) 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. 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, these results add weight to the argument that spraying where the pollinators are sensitive to the pesticide used decreases plant fecundity.

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. 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 (产卵,生育,结果) 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: a short life span, a narrow geographic range, an incapacity for vegetative propagation, and a dependence on a small number of insect-pollinator species. 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.   

4.       It can be inferred that which of the following is true of plant fecundity as it is defined in the passage? (why d and e are wrong?)本题是逻辑推理题,属于归纳题,先找原文: 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.

希望下次我不错了...

想问一下第1题，答案是C，为什么D不对？ 文章第二段讲了fecundity会受pesticide的影响，第三段讲fecundity与否对population的影响还未定， 不正好对应D吗？

1.Which of the following best summarizes the main point

  of the passage?

(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.

还是看不懂

Whatever decreaseà fecundity decrease (causes are sufficient to fecundity decrease充分条件)

(A) A plant’s fecundity decreases as the percentage of unpollinated flowers on the plant increases. Unpollinated flowers on that plant increases (是fecundity decreases的充分条件)

为什么a会正确，文中哪里有提到unpollinated flowers和fecundity的关系的句子吗？？

想请问第6题，找不到根据……

求救！