美国GRE出国考试模拟试题13
2011-09-29 11:19:00   来源：作文地带    双击单词自动翻译

作文地带导读：quite consistent with the wind dispersal of pollen, clouds　of which are released from some of the larger cones.about cycad pollination and what the structure of　most female cones suggests about that process.

　　美国GRE出国考试模拟试题13

　　Experiments show that insects can function as pollinators

　　of cycads, rare, palmlike tropical plants. Furthermore, cycads

　　removed from their native habitats—and therefore from

　　insects native to those habitats—are usually infertile. Nev-

　　(5) ertheless, anecdotal reports of wind pollination in cycads

　　cannot be ignored. The structure of cycads male cones is

　　quite consistent with the wind dispersal of pollen, clouds

　　of which are released from some of the larger cones. The

　　male cone of Cycas circinalis, for example, sheds almost

　　(10)100 cubic centimeters of pollen, most of which is probably

　　dispersed by wind. Still, many male cycad cones are com-

　　paratively small and thus produce far less pollen. Further-

　　more, the structure of most female cycad cones seems incon-

　　sistent with direct pollination by wind. Only in the Cycas

　　(15)genus are the females’ ovules accessible to airborne pollen,

　　since only in this genus are the ovules surrounded by a

　　loose ag美国GREgation of megasporophylls rather than by a tight

　　cone.

 

　　24.According to the passage, the size of a male cycad

　　cone directly influences which of the following?

　　(A) The arrangement of the male cone’s structural

　　elements

　　(B) The mechanism by which pollen is released from

　　the male cone.

　　(C) The de美国GREe to which the ovules of female cycads

　　are accessible to airborne pollen

　　(D) The male cone’s attractiveness to potential insect

　　pollinators

　　(E) The amount of pollen produced by the male cone

 

　　25. The passage suggests that which of the following is

　　true of the structure of cycad cones?

　　(A) The structure of cycad cones provides conclusive

　　evidence in favor of one particular explanation

　　of cycad pollination.

　　(B) The structure of cycad cones provides evidence

　　concerning what triggers the first step in the

　　pollination process.

　　(C) An irresolvable discrepancy exists between what

　　the structure of most male cycad cones suggests

　　about cycad pollination and what the structure of

　　most female cones suggests about that process.

　　(D) The structure of male cycad cones rules out a

　　possible mechanism for cycad pollination that is

　　suggested by the structure of most female cycad

　　cones.

　　(E) The structure of male cycad cones is consistent

　　with a certain means of cycad pollination, but

　　that means is inconsistent with the structure of