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GRE阅读:夏威夷地区植物种子的运输方式

2017-01-27 17:18:00来源：!新东方在线

　　GRE阅读:夏威夷地区植物种子的运输方式

　　Since the Hawaiian Islands have never been connected to other landmasses, the great variety of plants in Hawaii must be a result of thelong-distance dispersal of seeds, a process that requires both a method oftransport and an equivalence between the ecology of the source area and that ofthe recipient area.

　　There is some dispute about the method of transport involved. Somebiologists argue that ocean and air currents are responsible for the transportof plant seeds to Hawaii. Yet the results of flotation experiments and the lowtemperatures of air currents cast doubt on these hypotheses. More probable isbird transport, either externally, by accidental attachment of the seeds tofeathers, or internally, by the swallowing of fruit and subsequent excretion ofthe seeds. While it is likely that fewer varieties of plant seeds have reachedHawaii externally than internally, more varieties are known to be adapted toexternal than to internal transport.

　　17. The author of the passage is primarilyconcerned with

　　(A) discussingdifferent approaches biologists have taken to testing theories about thedistribution of plants in Hawaii

　　(B) discussingdifferent theories about the transport of plant seeds to Hawaii

　　(C) discussingthe extent to which air currents are responsible for the dispersal of plantseeds to Hawaii

　　(D) resolving adispute about the adaptability of plant seeds to bird transport

　　(E) resolving adispute about the ability of birds to carry plant seeds long distances

　　18. The author mentions the results of flotationexperiments on plant seeds (lines 10-12) most probably in order to

　　(A) support theclaim that the distribution of plants in Hawaii is the result of thelong-distance dispersal of seeds

　　(B) lendcredibility to the thesis that air currents provide a method of transport forplant seeds to Hawaii

　　(C) suggestthat the long-distance dispersal of seeds is a process that requires longperiods of time

　　(D) challengethe claim that ocean currents are responsible for the transport of plant seedsto Hawaii

　　(E) refute theclaim that Hawaiian flora evolved independently from flora in other parts ofthe world

　　19. It can be inferred from information in thepassage that the existence in alpine regions of Hawaii of a plant species thatalso grows in the southwestern United States would justify which of thefollowing conclusions?

　　(A) The ecology of thesouthwestern United States is similar in important respects to the ecology ofalpine regions of Hawaii.

　　(B) There are oceancurrents that flow from the southwestern United States to Hawaii.

　　(C) The plantspecies discovered in Hawaii must have traveled from the southwestern UnitedStates only very recently.

　　(D) The plantspecies discovered in Hawaii reached there by attaching to the feathers ofbirds migrating from the southwestern United States.

　　(E) The plantspecies discovered in Hawaii is especially well adapted to transport over longdistances.

　　20. The passage supplies information foranswering which of the following questions?

　　(A) Why doessuccessful long-distance dispersal of plant seeds require an equivalencebetween the ecology of the source area and that of the recipient area?

　　(B) Why aremore varieties of plant seeds adapted to external rather than to internal birdtransport?

　　(C) Whatvarieties of plant seeds are birds that fly long distances most likely toswallow?

　　(D) What is areason for accepting the long-distance dispersal of plant seeds as anexplanation for the origin of Hawaiian flora?

　　(E) Whatevidence do biologists cite to argue that ocean and air currents areresponsible for the transport of plant seeds to Hawaii?

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