Day07
知识点：
信息目的题与举例目的题
经典例题
Passage 50 短篇文章/难度中
There have been numerous well-documented extinctions of indigenous species caused by the introduction of non-indigenous predators and pathogens. However, surprisingly few extinctions of indigenous species can be attributed to competition from introduced species. For example, during the past 400 years, 4,000 plant species have been introduced into North America, and these non-indigenous plants currently account for ne arly 20 percent of North America’s plant species. Yet noevidence exists that any indigenous North American plant species became extinct as a result of competition from new species could mean that such extinctions take longer to occur than scientists initially believed or, alternatively, that extinctions are rarely caused by competition from non-indigenous species.
2. The author introduces statistics about North America’s non-indigenous plant species primarily in order
to
A. undermine a proposed explanation for the absence of any evidence for the occurrence of a particular phenomenon
B. contrast the effect of introduced plant species in North America with the effect that introduced animal species have had
C. suggest that North America’s indigenous plants ar e a domain in which there has been ample scope for a particular effect to have occurred
D. emphasize how much the ecology of North America has been affected over the past 400 years by the introduction of non-indigenous species
E. substantiate a claim about the overall effect that the introduction of non-indigenous species tends to have on indigenous populations
Passage 36
Astronomers have had difficulty accounting for certain planets discovered outside our solar system. Th
ey are called hot Jupiters because each is similar in mass to Jupiter, the largest solar-system planet, but orbits its parent star at a fraction of the distance at which Earth, let alone Jupiter, orbits the Sun. In the standard, solar-system-based theory of planetary formation, such as a massive planet could not form so close to a star. So most attempts to explain a hot Jupiter’s existence envision it forming farther away, then migrating inward. According to one hypothesis, the planet’s gravitational field tugs on the protoplanetary disk of dust and gas from which it formed. The disk exerts its own gravitational tug, and this interplay of forces robs the planet of momentum in its orbital path, forcing it to spiral in toward the star. According to another hypothesis, the planet’s gravitational field is so strong that it creates a groove in the disk, partitioning it into inner and outer regions; the resulting gravitational interactions between the planet and these regions cause the planet to lose orbital momentum and spiral inward. Another question remains: what prevents the planet from continuing its spiral until it collides with the star?
1. The author of the passage mentions “Earth” primarily in order to
A.stress the massive size of a hot Jupiter
C.imply that hot Jupiters are unlikely to harbor extraterrestrial life
D.point out differences between Earth and Jupiter with regard to their orbital distance from the Sun
E. illustrate how hot Jupiters might fit into the standard theory of planetary formation
Passage 145
When selecting a nest, the female of the river blenny (a small fish) appears to be sensitive to both size and orientation. Blennies deposit their eggs preferably in nests under large stones and in nests facing southeast. Southeast-facing nests contain larger egg clutches, a fact that cannot be completely explained by differences in nest stone sizes. Moreover, in a recent study, current speeds upstream of the nest and at the nest entrance were similar for nests facing southeast and those facing in other directions. A southeast-facing entrance per se thus seems to be the specific nest feature preferred by females, rather than the effect of selective positioning on current at nest entrance. The reasons for this preference are unclear, however.
2. The author of the passage considers “current speeds” in or der to
A. identify a factor that undermines the significance of nest stone size for female river blennies
B. indicate one possible advantage of river blenny nests that do not face southeastdocumented evidence
C. eliminate a possible explanation for a nest orientation tendency among female river blennies
D. indicate why female river blennies are sensitive to both size and orientation of possible nests
E. suggest a reason why many female blennies prefer southeast-facing nests Day07
信息目的题练习讲解
Passage 115 短篇文章/难度中
Although the passenger pigeons, now extinct, were abundant in eighteenth- and nineteenth-century America, archaeological studies at twelfth-century Cahokian sites in the present day United States examined household food trash and found that traces of passenger pigeon were quite rare. Given that the sites were close to a huge passenger pigeon roost documented by John James Audubon in the nineteenth century and that Cahokians consumed almost every other animal protein source available, the archaeologists conducting the studies concluded the passenger pigeon population had once been very limited before increasing dramatically in post-Columbian America. Other archaeologists have criticized those conclusions on the grounds that passenger pigeon bones would not be likely to be pres
erved. But all the archaeological projects found plenty of bird bones and even tiny bones from fish.
1. The author of the passage mentions “tiny bones from fish” primarily in order to
A. explain why traces of passenger pigeon are rare at Cahokian sites
B. support a claim about the wide variety of animal proteins in the Cahokian diet
C. provide evidence that confirms a theory about the extinction of the passenger pigeon
D. cast doubt on the conclusion reached by the archaeologists who conducted the studies discussed in the passage
E. counter an objection to an interpretation of the data obtained from Cahokian sites
参看分步练习
Passage 133
Some historians question the widely held belief that continually improving education led to gradual African American empowerment in the southern United States from the late nineteenth century through
the mid-twentieth century. They note that the development of Black educational institutions in the segregated South was never rapid or steady: disparities between Black and White schools sometimes grew in the early decades of the twentieth century. And African Americans’ educational gains did not bring commensurate economic gains. Starting in the 1940s, even as Black and White schools in the South moved steadily toward equality, Black southerners remained politically marginalized and experienced systematic job discrimination. Although Black schools had achieved near parity with White schools in per capita spending and teachers’ salaries by 1965, African Americans’ income still lagged behind that of Whites. Nonetheless, educational progress did contribute toward economic and political empowerment. African American s’ campaigns to support Black schools fostered a sense of community, nurtured political determination, and often increased literacy. More significantly, politically outspoken Black newspapers achieved record circulation during the 1940s, just as the literacy rate among African Americans approached 90 percent. Finally, the leadership of the Civil Rights movement of the 1960s was composed largely of graduates of Black colleges.
1. The author of the passage refers to the fact that “disparities between Black and White schools sometimes grew in the early decades of the twentieth century” most likely in order to
A. support the argument that the economic struggles of southern Blacks were largely due to education
al inequalities
B. give an example of the differences between Black schools in the early part of the twentieth century and Black schools starting in the 1940s
C. illustrate the unevenness of the progress made by Black schools in the southern United States
D. help explain why Black remained politically marginalized and experienced systematic job discrimination in the segregated South
E. provide evidence that educational progress was a precondition for economic progress in the segregated South
2. Which of the following best describes the purpose of the highlighted sentence?
A. It clarifies a point introduced in the preceding sentence.
B. It reiterates a point introduced in the first sentence of the passage.
C. It questions the accuracy of some of the evidence used to support the argument of the historians.
D. It introduces a perspective that runs contrary to the view of those who endorse the “belief.”
E. It qualifies the interpretation made by the historians.

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