OG48-9(再來一篇科學類文章，大家救救命呀)

网站 · 由 **agk99** » 2004-09-03 22:39

Passage 9，科學類型文章

Milankovitch proposed in the early twentieth century that the ice ages were caused by variations in the Earth’s orbit around the Sun(M在二十世紀初就說，冰河期是由地球繞太陽公轉造成). For sometime this theory was considered untestable, largely because there was no sufficiently precise chronology(年表) of the ice ages with which the orbital variations could be matched.

To establish such a chronology it is necessary to determine the relative amounts of land ice that existed at various times in the Earth’s past. A recent discovery makes such a determination possible: (必讀)relative land-ice volume for a given period can be deduced(推算、第52題的考點) from the ratio of two oxygen isotopes(同位素), 16 and 18, found in ocean sediments. Almost all the oxygen in water is oxygen 16, but a few molecules out of every thousand incorporate(包含)(但也有千分之幾的氧分子組成了較重的氧18) the heavier isotope 18(16還是比18多很多). When an ice age begins, the continental ice sheets grow, steadily reducing the amount of water evaporated(從海洋上蒸發) from the ocean that will eventually return to it(前後因果關係很不明確，因為既然量減少，但氧18卻反而更多?應當是蒸發大量後，氧才會大量流下?). Because heavier isotopes tend to be left behind when water evaporates from the ocean surfaces, the remaining ocean water becomes progressively enriched in oxygen 18. The degree of enrichment can be determined by analyzing ocean sediments of the period, because these sediments are composed of calcium carbonate(碳酸鈣?)shells of marine organisms, shells that were constructed with oxygen atoms drawn from the surrounding ocean. The higher the ratio of oxygen 18 to oxygen 16 in a sedimentary specimen, the more land ice there was when the sediment was laid down.(讀到後面也沒有什麼跳讀的問題了，根本是有讀沒有懂，看來科學文章真的很麻煩)第二段結論：大概第二段最後一句是關鍵，也就是氧18對氧16的比率是固定的，一旦檢測出比率上升，冰河期的面積就上升，如此一來，搭配第一段的結論，證明年表就確定可以做出來，就能印證M於二十世紀初所提倡的理論

As an indicator of shifts in the Earth’s climate, the isotope(明顯是承接第二段的說明) record has two advantages. (必讀)First, it is a global record(全球性的): there is remarkably little variation in isotope ratios in sedimentary specimens taken from different continental locations. Second, it is a more continuous record(連續性的) than that taken from rocks on land. Because of these advantages, sedimentary evidence can be dated with sufficient accuracy by radiometric methods to establish a precise chronology of the ice ages.(等於是呼應第一段，研究結論有著落) The dated isotope record shows that the fluctuations in global ice volume over the past several hundred thousand years have a pattern: an ice age occurs roughly once every 100,000 years. These data have established a strong connection between variations in the Earth’s orbit and the periodicity of the ice ages.
第三段結論，進一步介紹isotope的好處，包括這是全球性的證據，第二則是延續性的，因為這兩項優勢，藉由radiometric methods就能查出ice的年紀。此外，這套測試也發現，在過去數十萬年的變動中，每十年會有一次冰河期，這樣的時間在地球公轉以及冰河的周期中產生極大的連繫。

However, it is important to note that other factors, such as volcanic particulates or variations in the amount of sunlight received by the Earth, could potentially have affected the climate. The advantage of the Milankovitch theory is that it is testable: changes in the Earth’s orbit can be calculated and dated by applying Newton’s laws of gravity to progressively earlier configurations of the bodies in the solar system. Yet the lack of information about other possible factors affecting global climate does not make them unimportant.(所以其他未查明的因素也是重要的)

*49. In the passage, the author is primarily interested in (主題題型)
(A) suggesting an alternative to an outdated research method
(B) introducing a new research method that calls an accepted theory into question(x)
(C) emphasizing the instability of data gathered from the application of a new scientific method (x)
(D) presenting a theory and describing a new method to test that theory(x)
(E) initiating a debate about a widely accepted theory(x)
答案是D，答案無誤，並非對一個過時方法提出替代，因為並無替代問題

50. The author of the passage would be most likely to agree with which of the following statements about the Milankovitch theory?(細節題)
(A) It is the only possible explanation for the ice ages. (見最後一段)
(B) It is too limited to provide a plausible explanation for the ice ages, despite recent research findings. (x)
(C) It cannot be tested and confirmed until further research on volcanic activity is done. (x)
(D) It is one plausible explanation, though not the only one, for the ice ages. (三、四段)
(E) It is not a plausible explanation for the ice ages, although it has opened up promising possibilities for future research. (x)

*51. It can be inferred from the passage that the isotope record taken from ocean sediments would be less useful to researchers if which of the following were true?(推論題)
(A) It indicated that lighter isotopes of oxygen predominated at certain times.
(B) It had far more gaps(更多的間隔而非更多的連繫，當然不合文章要求) in its sequence than the record taken from rocks on land.
(C) It indicated that climate shifts did not occur every 100,000 years.
(D) It indicated that the ratios of oxygen 16 and oxygen 18 in ocean water were not consistent with those found in fresh water.
(E) It stretched back for only a million years.
答案是B

*52. According to the passage, which of the following is true of the ratios of oxygen isotopes in ocean sediments?(細節題)(A) They indicate that sediments found during an ice age contain more calcium carbonate than sediments formed at other times (文章沒說).
(B) They are less reliable than the evidence from rocks on land in determining the volume of land ice. (海中比陸地上可靠)
(C) They can be used to deduce the relative volume of land ice that was present when the sediment was laid down.
(D) They are more unpredictable during an ice age than in other climatic conditions.
(E) They can be used to determine atmospheric conditions at various times in the past.
答案是C

*53. It can be inferred from the passage that precipitation formed(結成冰) from evaporated ocean water has(這題是反過來的考點，問的是從海中蒸發的水氣有何特點)(推論)
(A) the same isotopic ratio as ocean water
(B) less oxygen 18 than does ocean water
(C) less oxygen 18 than has the ice contained in continental ice sheets
(D) a different isotopic composition than has precipitation formed from water on land(沒把握)
(E) more oxygen 16 than has precipitation formed from fresh water
答案是B，我做這題時一心一意想的是，蒸發後的結晶水和原本的海洋應是一致，但事實上，不一致，而且所擁有的氧18含量一定少於海洋

54. It can be inferred from the passage that calcium carbonate shells
(A) are not as susceptible(易受影響的) to deterioration as rocks
(B) are less common in sediments formed during an ice age
(C) are found only in areas that were once covered by land ice
(D) contain radioactive material that can be used to determine a sediment’s isotopic composition
(E) reflect the isotopic composition of the water at the time the shells were formed

結論：
科學類型文章講究的是細節，以及適度的專有名詞，六個選項絕大多數是考細節及推論，困難程度都不低，其中又以第53題最麻煩，讀不懂就是讀不懂，就一定錯
再辛苦也要定位，定到位置，再選答案
科學類型真不好讀，麻煩

由 **bear** » 2004-09-22 20:01

今天我也看了這篇文章, 想問53題
(C)選項的OG解釋說 , 應該改成 similar 才對即(oxygen 18 的多少在percipitation 和 the ice contained in continental ice sheets 是 similar的)

OG的解釋我已經看暈了....有沒有那位高手幫幫忙??? 實在不懂其中的關係.....
C is incorrect because the passage suggests that the water evaporated from the ocean contributes to the growth of continental ice sheets, which should therefore have an isotopic composition similar to that of the precipitation formed from evaporated ocean water.