GRE閱讀｜As Gilbert White, Darwin, and others observed long ago, all species appear to have the innate capacity to increase their numbers from generation to generation－熱血背包客莊ㄟ

As Gilbert White, Darwin, and others observed long ago, all species appear to have the innate capacity to increase their numbers from generation to generation. The task for ecologists is to untangle the environmental and biological factors that hold this intrinsic capacity for population growth in check over the long run. The great variety of dynamic behaviors exhibited by different populations makes this task more difficult: some populations remain roughly constant from year to year; others exhibit regular cycles of abundance and scarcity; still others vary wildly, with outbreaks and crashes that are in some cases plainly correlated with the weather, and in other cases not.

To impose some order on this kaleidoscope of patterns, one school of thought proposes dividing populations into two groups. These ecologists posit that the relatively steady populations have "density- dependent" growth parameters; that is, rates of birth, death, and migration which depend strongly on population density. The highly varying populations have "density-independent" growth parameters, with vital, rates buffeted by environmental events; these rates fluctuate in a way that is wholly independent of population density.

In order to understand the nature of the ecologist's investigation, we may think of the density-dependent effects on growth parameters as the "signal" ecologists are trying to isolate and interpret, one that tends to make the population increase from relatively low values or decrease from relatively high ones, while the density-independent effects act to produce "noise" in the population dynamics. For populations that remain relatively constant, or that oscillate around repeated cycles, the signal can be fairly easily characterized and its effects described, even though the causative biological mechanism may remain unknown. For irregularly fluctuating populations, we are likely to have too few observations to have any hope of extracting the signal from the overwhelming noise. But it now seems clear that all populations are regulated by a mixture of density-dependent and density-independent effects in varying proportions.

1.The author of the passage is primarily concerned with

(A) discussing two categories of factors that control population growth and assessing their relative importance

(B) describing how growth rates in natural populations fluctuate over time and explaining why these changes occur

(D) posing a fundamental question about environmental factors in population growth and presenting some currently accepted answers

(E) refuting a commonly accepted theory about population density and offering a new alternative

2. It can be inferred from the passage that the author considers the dichotomy discussed in the second paragraph to be

(A) applicable only to erratically fluctuating populations

(B) useful, but only if its limitations are recognized

(D) a complete and sufficient way to account for observed phenomena

(E) conceptually valid, but too confusing to apply on a practical basis

3.Which of the following statements can be inferred from the last paragraph?

(A) For irregularly fluctuating populations, doubling the number of observations made will probably result in the isolation of density-dependent effects.

(B) Density-dependent effects on population dynamics do not occur as frequently as do density-independent effects.

(C) At present, ecologists do not understand any of the underlying causes of the density-dependent effects they observe in population dynamics..

(D) Density-dependent effects on growth parameters are thought to be caused by some sort of biochemical "signaling" that ecologists hope eventually to understand.

(E) It is sometimes possible to infer the existence of a density-dependent factor controlling population growth without understanding its causative mechanism.

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

4.According to the passage, all of the following behaviors have been exhibited by different populations

(A) roughly constant population levels from year to year

(B) regular cycles of increases and decreases in numbers

結構分析：

這一篇我陷了～～卡在第三題，為了全盤理解，只能一句一句分析，並把得到的結論納入我的解題攻略中

第一段：

As Gilbert White, Darwin, and others observed long ago, all species appear to have the innate capacity to increase their numbers from generation to generation.

這句剛開始點出了一些研究者發現物種會有數量變大的趨勢，這表示著文章的主題，就是在討論物種族群的數量問題，但是這只給方向，我還是不知道他的文章寫作方式，也就是文體的展現，因此再往下看，然後其二是appear這個動詞某種程度有表達其不確定性，表面上看來不一定就是真的，所以就文章立場來說他是一個『主觀』的判定。

The task for ecologists is to untangle the environmental and biological factors that hold this intrinsic capacity for population growth in check over the long run.

前面提到The task，這是等價於untangle the environmental and biological factors，用定冠詞加上概念來做代稱，後面的『Be動詞＋to』，這裡稍微複習一下國中老師教過的，當我們看到此結構會有以下三種解釋，表：命中注定，理所當然，預定計畫，然而他必須要和The task有連結，所以此時意義為『預定計畫』，說明文章的目定性已經出來囉，就是要解開某個謎，這個謎是造成『反』數量增加的 the environmental and biological factors（因素），所以本文的寫法很有可能必為因果關係文，去解釋為什麼數量增加，原因在哪裡，但我不確定，要取決於下一段的發展。hold...in check就是阻擋的意思。大致理解是，給科學家的功課是想辦法解開長期阻擋族群個數成長本能的環境誘因跟生物誘因。但是因為that hold this intrinsic....這是關係代名詞的修飾子句，基本上不要去讀它，讀了反而會亂，因為第一句給你的是科學家覺得數量是一直增加的，可是這裡卻是說他們處理方式是找到『反』數量增加的因子，這樣不就亂掉了，照理說科學家後來想辦法去找出數量增加的因子這樣應該是比較符合正常邏輯。感覺上這一句想要說的是假設讓他們找不到阻抗因子我就可以證明族群是一直增加的，或是我想太多就只是單純第一句講說數目增加是看起來很像但實際上不是這樣，所以這句話才說既然不是想像中的那樣，那到底阻止她的因子在哪。

這樣一來，第一句說到科學家認為族群可能數量一直往上的，然後怎麼證明，就是找出the environmental and biological factors。到此兩句，主幹抓到。

The great variety of dynamic behaviors exhibited by different populations makes this task more difficult: some populations remain roughly constant from year to year; others exhibit regular cycles of abundance and scarcity; still others vary wildly, with outbreaks and crashes that are in some cases plainly correlated with the weather, and in other cases not.

有點長，但是我們可以從分號來做內容上的區隔，分號表示同向邏輯的補充說明訊號字，因此可視為等號，前後兩句子之間是講同一件事情，所以先來看前部分吧。講述實驗難度

The great variety of dynamic behaviors exhibited by different populations makes this task more difficult:

這裡引出跟主題句無關的內容，無緣無故跑出dynamic behaviors，後面的結論是difficult，所以他並沒有針對文章主軸點出任何進一步的內容，因為我看到this task代名詞，他只是說我們要對主題做總結的話，是件『苦差事』，算是在補充task ，往下『分號』方補充的東西，利用並列方式呈現，嗅到考點了，如果用並列方式來呈現 dynamic behaviors，表示等等考試並然有極大可能出except的題型，找出哪一個不是其中的behaviors，等等有出在看即可。

第二段：

To impose some order on this kaleidoscope of patterns, one school of thought proposes dividing populations into two groups.

this kaleidoscope of patterns,最好不要知道他是萬花筒，就當作是上一段的 The great variety of dynamic behaviors，的代稱，怎麼判斷，他跟前一句話之間沒有轉折詞，所以必須是邏輯同向，這使得那個你絕對看得懂的patterns去強迫對應到上一句話的The great variety。之後內容終於給出某人的意見說到必須分組討論two groups.再來畢竟他是該段第一句話，所以以下必然是對two groups展開，所以找一下這兩組到底是哪兩組這一段的任務便可結束，閱讀時在注意看看有沒有轉折即可，往下

These ecologists posit that the relatively steady populations have "density- dependent" growth parameters; that is, rates of birth, death, and migration which depend strongly on population density.

數量穩定＝ＤＤ＝bio(rates of birth, death, and migration)

The highly varying populations have "density-independent" growth parameters, with vital, rates buffeted by environmental events; these rates fluctuate in a way that is wholly independent of population density.

一直變化＝ＤＩＤ＝ env(weather)

很好，劇本就是分成“density- dependent” VS. “density-independent”，內容就不要去看了，沒轉折，而這兩個就是找出factors的『方法』也就是分組討論，哇！！那這樣在回想剛剛第一段的那個猜想都是錯的，我以為文章是要我找出到底是啥原因，可是這段講完之後發現其實，這個原因才是主題，已經知道有這些原因了，然後文章要說的是怎麼分辨出原因是哪一類。

第三段：

This dichotomy has its uses, but it can cause problems if taken too literally.

This dichotomy我不認識沒關係，只要認識this就好，這表示又是一個代名詞表示上面的東西有他的利用價值uses，後面重點來囉but it can cause problems if taken too literally.但是上面講的東西有問題啊，就是分兩組有問題，那這也是第三段的開頭，這們說接下來就要討論問題出在哪裡了，因此整個第三段必然是跟第二段取反的，第三段絕對是要針對反方論證做出解釋，沒有為什麼，就因為開頭第一句話是主題句，說上面的東西，有～問～題！！

For one thing, no population can be driven entirely by density-independent factors all the time.

來看怎麼證明有問題，這句話說『不可能』完全切開一分為二

No matter how severely or unpredictably birth, death and migration rates may be fluctuating around their long-term averages, if there were no density-dependent effects, the population would, in the long run, either increase or decrease without bound (barring a miracle by which gains and losses canceled exactly).

一分為二的結果就是tan⍬函數，所以他跟上一句結合起來剛好是一個因果，一個是定義域往90度走，一個是往-90度走。這也是支持開頭說『有問題』

For one thing，跟No matter一個表示舉例的字眼，一個表示強調的字眼，那邏輯上當然同向去支持本段的主題句，點出為何我說他是一個很大的問題，給出理由，所以屬細節那我們姑且就跳過吧。

Put another way, it may be that on average 99 percent of all deaths in a population arise from density-independent causes, and only one percent from factors varying with density.

感覺上好像是建立一個前提，看不到一個決定性的東西，所以必須跟下一句連結，這絕不是跟上一句去連結，因為another已經把兩個例子分割了，

The factors making up the one percent may seem unimportant, and their cause may be correspondingly hard to determine.

確實The factors的定冠詞把上一句的factors varying with density給連結了，後面給出『不重要』，暗示可以分，可是怎麼邏輯被改過去了，跟主題句的不一樣，所以極有可能下面有轉折字的封裝，果然看到yet，所以再把原本該有的邏輯再轉拉回來

Yet, whether recognized or not, they will usually determine the long-term average population density.

他們變動的平均值的因素必然就是“density- dependent” 和 “density-independent”，寫出they就表示缺一不可都必須考量到，不可分

第四段：

這段開頭又來回去第一段的開頭了，因為the nature of the ecologist's investigation對應到 all species appear to have the innate capacity to increase their numbers，往後吧，主幹在這裡：

we may think of the density-dependent effects on growth parameters as the "signal" ecologists are trying to isolate and interpret

不對喔！！這句話其實有再次定義ＤＤ跟ＤＩＤ分別是signal跟noise，這勾起我想仔細研究這句話的動機，所以來拆分

ㄅ：In order to understand the nature of the ecologist's investigation,

（這半部由介系詞開頭並且表目的用，不是主要子句，算是一個條件而已）

ㄆ：we may think of the density-dependent effects on growth parameters as the "signal" ecologists are trying to isolate and interpret

（這句話是主詞無誤，後方的ecologists are trying to isolate and interpret是關係代名詞限定用法修飾『訊號』the "signal" ）

ㄇ： one that tends to make the population increase from relatively low values or decrease from relatively high ones,

（這個是同位語，那個one就是逗點前面的the "signal"，後方increase from relatively low values or decrease from relatively high ones這是Ｖ型翻轉，所謂的黃金交叉跟死亡交叉，證明剛剛的tan⍬函數是錯的。）

ㄈ：while the density-independent effects act to produce "noise" in the population dynamics.

（主幹的第二部分出來了，利用while去做對象的區分）

然後以下兩句再針對兩個情況作區別，可以跳過去

For populations that remain relatively constant, or that oscillate around repeated cycles, the signal can be fairly easily characterized and its effects described, even though the causative biological mechanism may remain unknown.

For irregularly fluctuating populations, we are likely to have too few observations to have any hope of extracting the signal from the overwhelming noise.

這兩句就合在一起看吧，因為他是在做分類，看到For populations that remain relatively constant,以及For irregularly fluctuating populations,ＤＤ好處理，跟ＤＩＤ不好處理，這都是在做舉例，也是支持主幹用的。

But it now seems clear that all populations are regulated by a mixture of density-dependent and density-independent effects in varying proportions.

轉折再度出現，提到兩個因素都要考慮到才行，所以這個轉折也是一組封裝，把上面兩句話For populations 跟For irregularly給包裝在一起，好了文章讀完，總結就是數量的增減必須要考慮到density-dependent and density-independent，一樣保持第三段之後的邏輯，研究辦法是不能分的，以上是整篇通讀的結論，但是如果在考場當然是沒時間給你這樣玩，

因此我再來讀一次，並作些刪減：

This dichotomy has its uses, but it can cause problems if taken too literally. For one thing, no population can be driven entirely by density-independent factors all the time. No matter how severely or unpredictably birth, death and migration rates may be fluctuating around their long-term averages, if there were no density-dependent effects, the population would, in the long run, either increase or decrease without bound (barring a miracle by which gains and losses canceled exactly). Put another way, it may be that on average 99 percent of all deaths in a population arise from density-independent causes, and only one percent from factors varying with density. The factors making up the one percent may seem unimportant, and their cause may be correspondingly hard to determine.（For one thing表示舉例，No matter表示強調，another way表示另一個例子，所以都不需要看邏輯一定是延續該段主題句的） Yet, whether recognized or not, they will usually determine the long-term average population density.（兩個都要考慮表示不可分，跟主題句一樣邏輯，因為提到they表示對上面的內容作延續，是補充，照理說可以不用看，但是她關鍵在於那個轉折 Yet,是被封裝的，如果這句不跟上面的考慮，會覺得怎麼這裡幹嘛要接一個轉折）。

In order to understand the nature of the ecologist's investigation, we may think of the density-dependent effects on growth parameters as the "signal" ecologists are trying to isolate and interpret, one that tends to make the population increase from relatively low values or decrease from relatively high ones, while the density-independent effects act to produce "noise" in the population dynamics. For populations that remain relatively constant, or that oscillate around repeated cycles, the signal can be fairly easily characterized and its effects described, even though the causative biological mechanism may remain unknown. For irregularly fluctuating populations, we are likely to have too few observations to have any hope of extracting the signal from the overwhelming noise. （也是個別舉例，看到the signal表示前面有提過因此作為補充的角色不需要看，）But it now seems clear that all populations are regulated by a mixture of density-dependent and density-independent effects in varying proportions.（還是繞回來講密不可分）

好累啊這一篇，以上就是我認為關鍵必看的句子，共七句，其中厲害的是作者把第三段當轉折用，厲害啊～～一般都用however就帶過去了，他盡然能夠拉出一段話。

1.The author of the passage is primarily concerned with

(A) discussing two categories of factors that control population growth and assessing their relative importance

(B) describing how growth rates in natural populations fluctuate over time and explaining why these changes occur

(D) posing a fundamental question about environmental factors in population growth and presenting some currently accepted answers

(E) refuting a commonly accepted theory about population density and offering a new alternative

解題：

看到結構圖，主題是數量變因，要分兩個討論。所以關鍵字要有factors，增減數量，還有“分組”（Ｂ）（Ｃ）（Ｅ）先幹掉，（Ｄ）少了一個biological，不過他是細節裡的東西了，文章是從第二段開使是要怎麼找出因素的方法，不是對因素本身做評論或質疑，選（Ａ）

2. It can be inferred from the passage that the author considers the dichotomy discussed in the second paragraph to be

(A) applicable only to erratically fluctuating populations

(B) useful, but only if its limitations are recognized

(D) a complete and sufficient way to account for observed phenomena

(E) conceptually valid, but too confusing to apply on a practical basis

解題：

題目的the dichotomy出現在第三段啊，所以看到This dichotomy has its uses, but it can cause problems if taken too literally.作者把整個第二段用dichotomy給代替了，接下來就找他下的結論是啥即可，也就是後方的but，有問題，再用 if副詞子句說明條件，這裡表示在某條件下這個dichotomy問題很大，因此找個有『轉折』，並且有『邊界條件』的選項，選（Ｂ）

3.Which of the following statements can be inferred from the last paragraph?

(A) For irregularly fluctuating populations, doubling the number of observations made will probably result in the isolation of density-dependent effects.

(B) Density-dependent effects on population dynamics do not occur as frequently as do density-independent effects.

(C) At present, ecologists do not understand any of the underlying causes of the density-dependent effects they observe in population dynamics..

(D) Density-dependent effects on growth parameters are thought to be caused by some sort of biochemical "signaling" that ecologists hope eventually to understand.

(E) It is sometimes possible to infer the existence of a density-dependent factor controlling population growth without understanding its causative mechanism.

解題：

因為是問到整段在幹嘛，沒有比較對象出現，所以要找該段主旨，然後由最後一句的轉折知道要有『mix』混音得感覺，所以（Ａ）the isolation of density-dependent effects（Ｂ）Density-dependent effects do not occur（Ｃ）do not understand density-dependent effects選項都完全否決掉另外一半，先刪掉。（Ｄ）選項是一首台語歌叫針線情：『你是針，我是線，針線永遠相連接』，本文的錯誤點不是在biochemical，把biochemical不是biological當成錯誤點，這就不對了他們兩個是形容詞，在找答案的時候應該是以名詞為優先，錯誤點是在signaling，因為她把signaling和 Density-dependent直接『因果』連接，不是啊，他是當作比喻而已啊，要注意原文是『as』不是『is』啊，你不是針，我也不是線啊，但只是要說明你我形影不離密不可分。所以剩下（Ｅ）可以選。（Ｅ）possible to infer the existence of a density-dependent，他說ＤＤ可能有，雖然沒講到ＤＩＤ表示他默認有ＤＩＤ，所以兩個因素就有混到了，選（Ｅ）。

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

4.According to the passage, all of the following behaviors have been exhibited by different populations

(A) roughly constant population levels from year to year

(B) regular cycles of increases and decreases in numbers

抓到！！就是剛剛『分號』的那三組：

ㄅ：some populations remain roughly constant from year to year;

ㄆ：others exhibit regular cycles of abundance and scarcity;

ㄇ：still others vary wildly, with outbreaks and crashes that are in some cases plainly correlated with the weather, and in other cases not.

選（Ａ）（Ｂ）（Ｃ）

以上筆記供大夥參考若有錯誤再煩請指教