Flatfish, such as the flounder, are among the few vertebrates that lack approximate bilateral symmetry (symmetry in which structures to the left and right of the body‘s midline are mirror images). Most striking among the many asymmetries evident in an adult flatfish is eye placement: before maturity one eye migrates, so that in an adult flatfish both eyes are on the same side of the head. While in most species with asymmetries virtually all adults share the same asymmetry, members of the starry flounder species can be either left-eyed (both eyes on the left side of head) or right-eyed. In the waters between the United States and Japan, the starry flounder populations vary from about 50 percent left-eyed off the United States West Coast, through about 70 percent left-eyed halfway between the United States and Japan, to nearly 100 percent left-eyed off the Japanese coast.

 

Biologists call this kind of gradual variation over a certain geographic range a "cline" and interpret clines as strong indications that the variation is adaptive, a response to environmental differences. For the starry flounder this interpretation implies that a geometric difference (between fish that are mirror images of one another) is adaptive, that left-eyedness in the Japanese starry flounder has been selected for, which provokes a perplexing questions: what is the selective advantage in having both eyes on one side rather than on the other?

 

The ease with which a fish can reverse the effect of the sidedness of its eye asymmetry simply by turning around has caused biologists to study internal anatomy, especially the optic nerves, for the answer. In all flatfish the optic nerves cross, so that the right optic nerve is joined to the brain‘s left side and vice versa. This crossing introduces an asymmetry, as one optic nerve must cross above or below the other. G. H. Parker reasoned that if, for example, a flatfish‘s left eye migrated when the right optic nerve was on top, there would be a twisting of nerves, which might be mechanically disadvantageous. For starry flounders, then, the left-eyed variety would be selected against, since in a starry flounder the left optic nerve is uppermost.

 

The problem with the above explanation is that the Japanese starry flounder population is almost exclusively left-eyed, and natural selection never promotes a purely less advantageous variation. As other explanations proved equally untenable, biologists concluded that there is no important adaptive difference between left-eyedness and right-eyedness, and that the two characteristics are genetically associated with some other adaptively significant characteristic. This situation is one commonly encountered by evolutionary biologists, who must often decide whether a characteristic is adaptive or selectively neutral. As for the left-eyed and right-eyed flatfish, their difference, however striking, appears to be an evolutionary red herring.   

 

1. According to the passage, starry flounder differ from most other species of flatfish in that starry flounder

(A) are not basically bilaterally symmetric

(B) do not become asymmetric until adulthood

(C) do not all share the same asymmetry

(D) have both eyes on the same side of the head

(E) tend to cluster in only certain geographic regions

  

For the following question, consider each of the choices separately and select all that apply

2. The author would be most likely to agree with which of the following statements about left-eyedness and right-eyedness in the starry flounder?

(A) They are adaptive variations by the starry flounder to environmental differences.

(B) They do not seem to give obvious selective advantages to the starry flounder.

(C) They occur in different proportions in different locations.

  

3. According to the passage, a possible disadvantage associated with eye migration in flatfish is that the optic nerves can

(A) adhere to one another

(B) detach from the eyes

(C) cross

(D) stretch

(E) twist

  

4. Which of the following best describes the organization of the passage as a whole?

(A) A phenomenon is described and an interpretation presented and rejected.

(B) A generalization is made and supporting evidence is supplied and weighed.

(C) A contradiction is noted and a resolution is suggested and then modified.

(D) A series of observations is presented and explained in terms of the dominant theory.

(E) A hypothesis is introduced and corroborated in the light of new evidence.

 

結構分析:

第一段:

Flatfish, such as the flounder, are among the few vertebrates that lack approximate bilateral symmetry (symmetry in which structures to the left and right of the body‘s midline are mirror images)括號內容屬補充所以跳過. Most striking among the many asymmetries evident in an adult flatfish is eye placement: before maturity one eye migrates, so that in an adult flatfish both eyes are on the same side of the head.(Most表示做分類位於大部分,所以相對忽略少部分的東西,故視為特別舉例,咱們老規局跳過) While in most species with asymmetries virtually all adults share the same asymmetry, members of the starry flounder species can be either left-eyed (both eyes on the left side of head) or right-eyed.(雖然有轉折,不過他是句內轉折用於將in most species和其他物種分類討論,同樣屬於細節的舉例分析分門別類)In the waters between the United States and Japan, the starry flounder populations vary from about 50 percent left-eyed off the United States West Coast, through about 70 percent left-eyed halfway between the United States and Japan, to nearly 100 percent left-eyed off the Japanese coast.(看到地名而且也在分類,所以還是細節先跳過別看)

因此第一段主幹就是『確認』比目魚缺少對稱性,因為給了很多舉例啊。

 

第二段:

Biologists call this kind of gradual variation over a certain geographic range a "cline" and interpret clines as strong indications that the variation is adaptive, a response to environmental differences.For the starry flounder this interpretation implies that a geometric difference (between fish that are mirror images of one another) is adaptive, that left-eyedness in the Japanese starry flounder has been selected for, which provokes a perplexing questions:(開頭For the starry flounder 出現定冠詞,而且還有特定的比目魚,表示前面的內容繼續延伸,所以刪除) what is the selective advantage in having both eyes on one side rather than on the other?

第二段已開始直接用this kind去承接上面一段,可是他並不是在承接主幹,反而補充細節,因為gradual variation主題連提都沒提過,所以連貫下來這文章在偏向討論為什麼比目魚要長成這副德性,難道真的是朱元璋吃魚吃到一半放生就活過來的,所以才會感覺是扁平的,這都是可能的原因,這也帶出後面句尾的『問號』,問到他們長這樣到底好處是啥,所以文章已經轉型囉,原本開頭說有一種魚不對稱,接著第二段開頭說跟地緣有關吧,句尾直接跳成好吧那我承認他長得確實怪,那他這種被地緣關係導致的外表對他好處又是什麼。

 

第三段:

The ease with which a fish can reverse the effect of the sidedness of its eye asymmetry simply by turning around has caused biologists to study internal anatomy, especially the optic nerves, for the answer. In all flatfish the optic nerves cross, so that the right optic nerve is joined to the brain‘s left side and vice versa.(紅字部分都表示提過再補充,所以略,而且so that也是一個在說明原因來由的邏輯字,不是主幹) This crossing introduces an asymmetry, as one optic nerve must cross above or below the other.(同樣是代名詞開頭補充,跳過) G. H. Parker reasoned that if, for example, a flatfish‘s left eye migrated when the right optic nerve was on top, there would be a twisting of nerves, which might be mechanically disadvantageous.(舉例表正向邏輯的延續,支持主幹用的,所以也是補充,因此我再跳) For starry flounders, then, the left-eyed variety would be selected against, since in a starry flounder the left optic nerve is uppermost.(這也是分類舉例,就是SF這類都比較偏好左眼神經在上,但是不管啊這不是主幹啊,只能說他在支持主題句說長成這樣是因為跟神經有關)

所以該段又是只看第一句即可,抓關鍵字就是optic nerves回答第二段

 

第四段:

The problem with the above explanation is that the Japanese starry flounder population is almost exclusively left-eyed, and natural selection never promotes a purely less advantageous variation. As other explanations proved equally untenable, biologists concluded that there is no important adaptive difference between left-eyedness and right-eyedness, and that the two characteristics are genetically associated with some other adaptively significant characteristic. This situation is one commonly encountered by evolutionary biologists, who must often decide whether a characteristic is adaptive or selectively neutral. As for the left-eyed and right-eyed flatfish, their difference, however striking, appears to be an evolutionary red herring.   

第四段開頭給個problem,準備打槍上方觀點,說神經不是答案,那接下來內容都請跳過,因為other explanations untenable這是並列結構,繼續承接他還是個問題,This situation代名詞,補充,直接看到段尾,出現轉折,所以the left-eyed and right-eyed flatfish, their difference這個不同的長相是因為evolutionary red herring. 『ERH』後面單字認不認識不重要,他其實是一個諺語,我管那麼多幹嗎,however取反就對了,做題羅。

 

1. According to the passage, starry flounder differ from most other species of flatfish in that starry flounder

(A) are not basically bilaterally symmetric

(B) do not become asymmetric until adulthood

(C) do not all share the same asymmetry

(D) have both eyes on the same side of the head

(E) tend to cluster in only certain geographic regions

 

解題:

找出SF的不同,先找出第一次出現SF的地方,而且要有不同出,所以必然有比較,兩物種之間差異,所以找句內轉折的成功率會很高,

While in most species with asymmetries virtually all adults share the same asymmetry, members of the starry flounder species can be either left-eyed (both eyes on the left side of head) or right-eyed.

所以內容對比就是same asymmetry,選(C)

 

For the following question, consider each of the choices separately and select all that apply

2. The author would be most likely to agree with which of the following statements about left-eyedness and right-eyedness in the starry flounder?

(A) They are adaptive variations by the starry flounder to environmental differences.

(B) They do not seem to give obvious selective advantages to the starry flounder.

(C) They occur in different proportions in different locations.

  

解題:

他是多選題,所以題目可能會有並列結構讓我們去對應選項答案,抓關鍵字SF的left-eyedness and right-eyedness

由上一題第一次提到SF可左可右的眼睛配對,因此往下找才有答案,對應句子人選如以下:

壹:In the waters between the United States and Japan, the starry flounder populations vary from about 50 percent left-eyed off the United States West Coast, through about 70 percent left-eyed halfway between the United States and Japan, to nearly 100 percent left-eyed off the Japanese coast.

句子太長抓主幹,大概就是講左眼分佈變化,看不懂沒關係直接放掉,因為剛剛在抓結構的時候曾經探討對第二段的開頭就是在補充說明這一句話的,因此關鍵就是那個geographic variation

 

貳:Biologists call this kind of gradual variation over a certain geographic range a "cline" and interpret clines as strong indications that the variation is adaptive, a response to environmental differences.

(A)選項會中招是因為the variation is adaptive, a response to environmental differences.這些東西是在修飾"cline",跟魚魚一點關係都沒有,那個and是分水嶺。

 

參:For the starry flounder this interpretation implies that a geometric difference (between fish that are mirror images of one another) is adaptive, that left-eyedness in the Japanese starry flounder has been selected for, which provokes a perplexing questions: what is the selective advantage in having both eyes on one side rather than on the other?

這句說明GEO是可行的,並給出問題,所以意味,有問題表示這個優勢不確定,選(B),(C)

 

3. According to the passage, a possible disadvantage associated with eye migration in flatfish is that the optic nerves can

(A) adhere to one another

(B) detach from the eyes

(C) cross

(D) stretch

(E) twist

 

解題:

這簡直是超級細節題,內容在這句:

G. H. Parker reasoned that if, for example, a flatfish‘s left eye migrated when the right optic nerve was on top, there would be a twisting of nerves, which might be mechanically disadvantageous.

可是怎麼找到倒是一個難題,我的選法:有視神經缺點,那就是直接定位到第四段開頭The problem with the above explanation ,哇~~這意思是叫我們看上面的解釋,再來不可能往第四段的第二句找,因為 other explanations有邏輯分割的效果,講別的事了,既然他說是找某理論的解釋,所以絕不是從主題句開始找,這必然是在細節,explanation的定義是給個理由來說服,所以對應到:for example,如此一來,a flatfish‘s left eye migrated,disadvantageous也有了,句子看完之後,選(E)

  

4. Which of the following best describes the organization of the passage as a whole?

(A) A phenomenon is described and an interpretation presented and rejected.

(B) A generalization is made and supporting evidence is supplied and weighed.

(C) A contradiction is noted and a resolution is suggested and then modified.

(D) A series of observations is presented and explained in terms of the dominant theory.

(E) A hypothesis is introduced and corroborated in the light of new evidence.

 

解題:

這個結構圖對一對答案就現形,首先一個SH的長相問題,然後討論到為何長這樣(這裡開始已經是第二層細節的展開),最後反駁GEO,給出ERH,這中間有轉折,所以答案只能是(A)rejected,(C)contradiction,二選一,(C)的錯誤點為他們不是兩觀點的吵架,例如說一個認為SF長得很不對稱,然後另一組人馬說SF長得很對稱,這才能形成所謂的觀點對立矛盾,本文字已經默認SF長得很不對稱,然後進入討論倒底為何,施主是何苦,所以選(A)

 

 

 

以上筆記供大夥參考若有錯誤再煩請指教 

 

 

 


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