問題詳情

III.Passage completion (10%)Biodiversity is not just a matter of tigers and whales，or butterflies and trees. It is also about _21— creatures too small to see thatlive in numbers too large to count in ways too numerous to imagine. In that _22_，the discovery by Curtis Suttle of the Universityof British Columbia and his colleagues of a critter they propose to call Cafeteria roenbergensis virus, or CroV, should not be surprising. CroV is not a very virus-like virus. It has 544 genes，compared with the dozen or so that most viruses _23—. Also, it may be able to make its own proteins—a task that viruses usually delegate to the molecular machinery of the cells they infect.CroV, as its full name suggests, is a parasite of Cafeteria roenbergensis, a single-celled planktonic organism that was itself discovered only in 1988. Despite the recentness of its discovery, C. roenbergensis is one of the commonest creatures on the planet. It is also reckoned by some, _24— it hunts down and eats bacteria, to be the most abundant predator on Earth. It is found in every ocean. The samples of C. roenbergensis from which Dr Suttle and his team extracted their quarry were collected off the coast of Texas.Those who like their categories —25 may wonder whether viruses are alive or not. Wise biologists do not struggle too muchwith such questions. Viruses have genes, can reproduce and are _26 to the evolutionary pressures imposed by natural selection.That is enough for biology to claim them. As for CroV, those 544 genes (_27— 730,000 base pairs, the DNA letters in which thelanguage of the genes is written) mean its genome is bigger than those of several bacteria~creatures which everyone agrees are alive.The problem with categorical thinking in biology is that evolution does not work like that. It actually works by whatever worksworking. If an organism can successfully _28 part of the business of metabolism to another while retaining the rest itself, ratherthan offloading the whole lot as most viruses do, then there are no rules to stop it happening. CroV seems to do just that. Besides thegenes that relate to protein synthesis，it has others encoding DNA repair mechanisms 29 those involved with protein recyclingand signaling within cells. This is not mere hijacking. It is tantamount to a complete personality transplant for the infected cell.A whole new chapter of life，in other words，has been opened This discovery，then—andfe^Srjlier one of C. roenbergensis itself—speak —30—, albeit in a microscopic language, about biodiversity. Two centuries after Carl Linnaeus invented the system now used to describe it, and a century after Charles Darwin worked out what causes it, the ability of that diversity to surprise is still
(A) context
(B) cut and dried
(C) encompassing
(D) given that
(E) volumes(AB) sport(AC) as well as(AD) myriad(AE) constituted(BC) subcontract(BD) susceptible(BE) but that
21

參考答案

答案：A,D
難度：困難0.25
統計：A(1),B(0),C(0),D(1),E(0)

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