尚友阅读课程第24次课

1、陈琦GRE团队阅读长线班Since the Hawaiian Islands have never been connected to other land masses, the great variety of plants in Hawaii must be a result of the long-distance dispersal of seeds, a process that requires both a method of transport and an equivalence between the ecology of the source area and that

2、 of the recipient area.There is some dispute about the method of transport involved. Some biologists argue that ocean and air currents are responsible for the transport of plant seeds to Hawaii. Yet the results of flotation experiments and the low temperatures of air currents cast doubt on these hyp

3、otheses. More probable is bird transport, either externally, by accidental attachment of the seeds to feathers, or internally, by the swallowing of fruit and subsequent excretion of the seeds. While it is likely that fewer varieties of plant seeds have reached Hawaii externally than internally, more

4、 varieties are known to be adapted to external than to internal transport.Since the Hawaiian Islands have never been connected to other land masses, the great variety of plants in Hawaii must be a result of the long-distance dispersal of seeds, a process that requires both a method of transport and

5、an equivalence between the ecology of the source area and that of the recipient area.There is some dispute about the method of transport involved. Some biologists argue that ocean and air currents are responsible for the transport of plant seeds to Hawaii. Yet the results of flotation experiments an

6、d the low temperatures of air currents cast doubt on these hypotheses. More probable is bird transport, either externally, by accidental attachment of the seeds to feathers, or internally, by the swallowing of fruit and subsequent excretion of the seeds. While it is likely that fewer varieties of pl

7、ant seeds have reached Hawaii externally than internally, more varieties are known to be adapted to external than to internal transport.17. The author of the passage is primarily concerned with(A) discussing different approaches biologists have taken to testing theories about the distribution of pla

8、nts in Hawaii(B) discussing different theories about the transport of plant seeds to Hawaii(C) discussing the extent to which air currents are responsible for the dispersal of plant seeds to Hawaii(D) resolving a dispute about the adaptability of plant seeds to bird transport(E) resolving a dispute

9、about the ability of birds to carry plant seeds long distancesSince the Hawaiian Islands have never been connected to other land masses, the great variety of plants in Hawaii must be a result of the long-distance dispersal of seeds, a process that requires both a method of transport and an equivalen

10、ce between the ecology of the source area and that of the recipient area.There is some dispute about the method of transport involved. Some biologists argue that ocean and air currents are responsible for the transport of plant seeds to Hawaii. Yet the results of flotation experiments and the low te

11、mperatures of air currents cast doubt on these hypotheses. More probable is bird transport, either externally, by accidental attachment of the seeds to feathers, or internally, by the swallowing of fruit and subsequent excretion of the seeds. While it is likely that fewer varieties of plant seeds ha

12、ve reached Hawaii externally than internally, more varieties are known to be adapted to external than to internal transport.18. The author mentions the results of flotation experiments on plant seeds (lines 10-12) most probably in order to(A) support the claim that the distribution of plants in Hawa

13、ii is the result of the long-distance dispersal of seeds(B) lend credibility to the thesis that air currents provide a method of transport for plant seeds to Hawaii(C) suggest that the long-distance dispersal of seeds is a process that requires long periods of time(D) challenge the claim that ocean

14、currents are responsible for the transport of plant seeds to Hawaii(E) refute the claim that Hawaiian flora evolved independently from flora in other parts of the worldSince the Hawaiian Islands have never been connected to other land masses, the great variety of plants in Hawaii must be a result of

15、 the long-distance dispersal of seeds, a process that requires both a method of transport and an equivalence between the ecology of the source area and that of the recipient area.There is some dispute about the method of transport involved. Some biologists argue that ocean and air currents are respo

16、nsible for the transport of plant seeds to Hawaii. Yet the results of flotation experiments and the low temperatures of air currents cast doubt on these hypotheses. More probable is bird transport, either externally, by accidental attachment of the seeds to feathers, or internally, by the swallowing

17、 of fruit and subsequent excretion of the seeds. While it is likely that fewer varieties of plant seeds have reached Hawaii externally than internally, more varieties are known to be adapted to external than to internal transport.19. It can be inferred from information in the passage that the existe

18、nce in alpine regions of Hawaii of a plant species that also grows in the southwestern United States would justify which of the following conclusions?(A) The ecology of the southwestern United States is similar in important respects to the ecology of alpine regions of Hawaii.(B) There are ocean curr

19、ents that flow from the southwestern United States to Hawaii.(C) The plant species discovered in Hawaii must have traveled from the southwestern United States only very recently.(D) The plant species discovered in Hawaii reached there by attaching to the feathers of birds migrating from the southwes

20、tern United States.(E) The plant species discovered in Hawaii is especially well adapted to transport over long distances.Since the Hawaiian Islands have never been connected to other land masses, the great variety of plants in Hawaii must be a result of the long-distance dispersal of seeds, a proce

21、ss that requires both a method of transport and an equivalence between the ecology of the source area and that of the recipient area.There is some dispute about the method of transport involved. Some biologists argue that ocean and air currents are responsible for the transport of plant seeds to Haw

22、aii. Yet the results of flotation experiments and the low temperatures of air currents cast doubt on these hypotheses. More probable is bird transport, either externally, by accidental attachment of the seeds to feathers, or internally, by the swallowing of fruit and subsequent excretion of the seed

23、s. While it is likely that fewer varieties of plant seeds have reached Hawaii externally than internally, more varieties are known to be adapted to external than to internal transport.20. The passage supplies information for answering which of the following questions?(A) Why does successful long-dis

24、tance dispersal of plant seeds require an equivalence between the ecology of the source area and that of the recipient area?(B) Why are more varieties of plant seeds adapted to external rather than to internal bird transport?(C) What varieties of plant seeds are birds that fly long distances most li

25、kely to swallow?(D) What is a reason for accepting the long-distance dispersal of plant seeds as an explanation for the origin of Hawaiian flora?(E) What evidence do biologists cite to argue that ocean and air currents are responsible for the transport of plant seeds to Hawaii?One of the questions o

26、f interest in the study of the evolution of spiders is whether the weaving of orb webs evolved only once or several times. About half the 35,000 known kinds of spiders make webs; a third of the web weavers make orb webs. Since most orb weavers belong either to the Araneidae or the Uloboridae familie

27、s, the origin of the orb web can be determined only by ascertaining whether the families are related.Recent taxonomic analysis of individuals from both families indicates that the families evolved from different ancestors, thereby contradicting Wiehles theory. This theory postulates that the familie

28、s must be related, based on the assumption that complex behavior, such as web building, could evolve only once. According to Kullman, web structure is the only characteristic that suggests a relationship between families. The families differ in appearance, structure of body hair, and arrangement of

29、eyes. Only Uloborids lack venom glands. Further identification and study of characteristic features will undoubtedly a 17. The primary purpose of the passage is to(A) settle the question of whether orb webs evolved once or more than once(B) describe scientific speculation concerning an issue related

30、 to the evolution of orb webs(C) analyze the differences between the characteristic features of spiders in the Araneidae and Uloboridae families(D) question the methods used by earlier investigators of the habits of spiders(E) demonstrate that Araneidae spiders are not related to Uloboridae spidersO

31、ne of the questions of interest in the study of the evolution of spiders is whether the weaving of orb webs evolved only once or several times. About half the 35,000 known kinds of spiders make webs; a third of the web weavers make orb webs. Since most orb weavers belong either to the Araneidae or t

32、he Uloboridae families, the origin of the orb web can be determined only by ascertaining whether the families are related.Recent taxonomic analysis of individuals from both families indicates that the families evolved from different ancestors, thereby contradicting Wiehles theory. This theory postul

33、ates that the families must be related, based on the assumption that complex behavior, such as web building, could evolve only once. According to Kullman, web structure is the only characteristic that suggests a relationship between families. The families differ in appearance, structure of body hair

34、, and arrangement of eyes. Only Uloborids lack venom glands. Further identification and study of characteristic features will undoubtedly answer the question of the evolution of the orb web. 18. It can be inferred from the passage that all orb-weaving spiders belong to types of spiders that(A) lack

35、venom glands(B) are included either in the Uloboridae or Araneidae families(C) share few characteristic features with other spider types(D) comprise less than a third of all known types of spiders(E) are more recently evolved than other types of spidersOne of the questions of interest in the study o

36、f the evolution of spiders is whether the weaving of orb webs evolved only once or several times. About half the 35,000 known kinds of spiders make webs; a third of the web weavers make orb webs. Since most orb weavers belong either to the Araneidae or the Uloboridae families, the origin of the orb

37、web can be determined only by ascertaining whether the families are related.Recent taxonomic analysis of individuals from both families indicates that the families evolved from different ancestors, thereby contradicting Wiehles theory. This theory postulates that the families must be related, based

38、on the assumption that complex behavior, such as web building, could evolve only once. According to Kullman, web structure is the only characteristic that suggests a relationship between families. The families differ in appearance, structure of body hair, and arrangement of eyes. Only Uloborids lack

39、 venom glands. Further identification and study of characteristic features will undoubtedly answer the question of the evolution of the orb web. 19. According to the passage, members of the Araneidae family can be distinguished from members of the Uloboridae family by all of the following EXCEPT:(A)

40、 the presence of venom glands(B) the type of web they spin(C) the structure of their body hair(D) the arrangement of their eyes(E) their appearanceOne of the questions of interest in the study of the evolution of spiders is whether the weaving of orb webs evolved only once or several times. About ha

41、lf the 35,000 known kinds of spiders make webs; a third of the web weavers make orb webs. Since most orb weavers belong either to the Araneidae or the Uloboridae families, the origin of the orb web can be determined only by ascertaining whether the families are related.Recent taxonomic analysis of i

42、ndividuals from both families indicates that the families evolved from different ancestors, thereby contradicting Wiehles theory. This theory postulates that the families must be related, based on the assumption that complex behavior, such as web building, could evolve only once. According to Kullma

43、n, web structure is the only characteristic that suggests a relationship between families. The families differ in appearance, structure of body hair, and arrangement of eyes. Only Uloborids lack venom glands. Further identification and study of characteristic features will undoubtedly answer the que

44、stion of the evolution of the orb web. 20. Which of the following statements, if true, most weakens Wiehles theory that complex behavior could evolve only once?(A) Horses, introduced to the New World by the Spaniards, thrived under diverse climatic conditions.(B) Plants of the Palmaceae family, desc

45、endants of a common ancestor, evolved unique seed forms even though the plants occupy similar habitats throughout the world.(C) All mammals are descended from a small, rodentlike animal whose physical characteristics in some form are found in all its descendants.(D) Plants in the Cactaceae and Eupho

46、rbiaceae families, although they often look alike and have developed similar mechanisms to meet the rigors of the desert, evolved independently.(E) The Cuban anole, which was recently introduced in the Florida wilds, is quickly replacing the native Florida chameleon because the anole has no competit

47、ors.One of the questions of interest in the study of the evolution of spiders is whether the weaving of orb webs evolved only once or several times. About half the 35,000 known kinds of spiders make webs; a third of the web weavers make orb webs. Since most orb weavers belong either to the Araneidae

48、 or the Uloboridae families, the origin of the orb web can be determined only by ascertaining whether the families are related.Recent taxonomic analysis of individuals from both families indicates that the families evolved from different ancestors, thereby contradicting Wiehles theory. This theory p

49、ostulates that the families must be related, based on the assumption that complex behavior, such as web building, could evolve only once. According to Kullman, web structure is the only characteristic that suggests a relationship between families. The families differ in appearance, structure of body

50、 hair, and arrangement of eyes. Only Uloborids lack venom glands. Further identification and study of characteristic features will undoubtedly answer the question of the evolution of the orb web. One of the simplest and best known kinds of crystal is the ionic salt, of which a typical example is sod

51、ium chloride or ordinary table salt. The fundamental components of an ionic salt are ions: atoms or molecules that have e electrically charged by gaining or losing one or more electrons. In forming sodium chloride, for example, sodium atoms give up an electron (thereby ing positively charged) and ch

52、lorine atoms gain an electron (thereby ing negatively charged). The ions are attracted to one another by their opposite charges, and they stack together compactly, like tightly packed spheres.Recently, scientists at Michigan State University created a new kind of crystal called an electride. In elec

53、trides, the anions (negative ions) are completely replaced by electrons, which are trapped in naturally formed cavities within a framework of regularly stacked cations (positive ions). Electrides are the first examples of ionic salts in which all these anionic sites are occupied solely by electrons.

54、Unlike other types of anions, anionic electrons do not behave as if they were simple charged spheres. In particular, because of their low mass and their tendency to interact with one another over great distances, they cannot be “pinned down” to any one location. Instead, they wander close to and amo

55、ng the atoms lining the cavity and interact with electrons in nearby cavities, perhaps changing places with them.The properties of an electride depend largely on the distance between the cavities that hold trapped electrons. When the trapped electrons are far apart, they do not interact strongly, an

56、d so behave somewhat like an array of isolated negative charges. When they are closer together, they begin to display properties associated with large ensembles of identical particles. When they are still closer, the ensemble properties dominate and the electrons “delocalize”: they are no longer tig

57、htly bound within individual cavities but are more or less free to pass through the spaces within the frame-work of positive ions.By synthesizing electrides from a variety of materials, one can vary the geometry of the anionic cavities and their relation to the surrounding cations. The resulting pro

58、perties may make it possible for electrides to e a basis for economically useful new materials and devices. For instance, because the electrons in some electrides are very weakly bound, these crystals could be effective as photosensitive detectors, in which an impinging photon liberates an electron,

59、 resulting in a small electric current. The same weak binding could also make electrides useful in solar-energy converters and as cathodes in batteries. One obstacle is the tendency of electrides to pose through reaction with air and water. Researchers are seeking ways to increase their stability.21

60、. The passage is primarily concerned with discussing(A) a way to isolate electrons(B) the characteristics of a new kind of crystal(C) the structure of an ionic salt(D) commercial uses for electrides(E) the properties of ions22. In the first paragraph, the author is primarily concerned with(A) introd