TOEFL Reading --- Detailed Factual Information 事實細節題:
TPO-27
What causes the predator-prey oscillations? Do increasing numbers of hares
lead to overharvesting of plants, which in turn results in reduced hare
populations, or do increasing numbers of lynx lead to overharvesting of hares?
Field experiments carried out by Charles Krebs and coworkers in 1992 provide
an answer. Krebs investigated experimental plots in Canada's Yukon territory
that contained hare populations. When food was added to these plots (no food
effect) and predators were excluded (no predator effect) from an experimental
area, hare numbers increased tenfold and stayed there -the cycle was lost.
However, the cycle was retained if either of the factors was allowed to operate
alone: if predators were excluded but food was not added (food effect alone),
or if food was added in the presence of predators (predator effect alone).
Thus, both factors can affect the cycle, which, in practice, seems to be
generated by the conjunction of the two factors.
1. According to paragraph 6, which of the following was true of the hare
population cycle in Krebs's experiment?
(A) The effects of providing food while at the same time introducing predators
cancelled each other, so there was no cycle.
(B) The cycle existed when either the food supply was limited or there were
predators.
(C) There was a cycle when there were no predators and food was supplied.
(D) If the hares had places to hide from the lynx, the hare population
increased tenfold and then remained at that level.
TOEFL Reading 之事實細節題型(Detailed Factual Information), 其作答原則, 根據題
幹之敘述, 尋索出關鍵字詞, 回原文段落定位, 再進行判斷.
根據第六段, 關於Krebs 對於野兔之數量循環所進行實驗中, 何者正確?
關鍵字詞--- Krebs experiments
原文定位--- Field experiments carried out by Charles Krebs and coworkers in
1992 provide an answer. Krebs investigated experimental plots in Canada's
Yukon territory that contained hare populations. When food was added to these
plots (no food effect) and predators were excluded (no predator effect) from an
experimental area, hare numbers increased tenfold and stayed there -the cycle
was lost. However, the cycle was retained if either of the factors was allowed
to operate alone: if predators were excluded but food was not added (food
effect alone), or if food was added in the presence of predators (predator
effect alone).
此篇章第三段段尾訊息: Two factors appear to be generating the cycle: food
plants and predators.
兩個因素產生物種數量之循環機制: 食物與掠食者.
故而研究人員為了解何種因素導致predator-prey oscillations , 因此進行相關的田
野實驗.
Krebs 所進行實驗中, 當食物加入此實驗計畫中(即無食物之影響), 而且掠食者亦
排除在外(無掠食者之影響), 則該數量之循環即消失.
然而, 一旦上述之兩因素有何一個, 即假如掠食者被排除, 但食物不增加; 或假如食
物增加進來, 且掠食者出現, 此時該循環則又可存在.
答案為 B.
根據第六段, 關於Krebs 對於野兔之數量循環所進行實驗中, 何者正確?
關鍵字詞--- Krebs experiments
原文定位--- Field experiments carried out by Charles Krebs and coworkers in 1992 provide an answer. Krebs investigated experimental plots in Canada's Yukon territory that contained hare populations. When food was added to these plots (no food effect) and predators were excluded (no predator effect) from an experimental area, hare numbers increased tenfold and stayed there -the cycle was lost. However, the cycle was retained if either of the factors was allowed to operate alone: if predators were
excluded but food was not added (food effect alone), or if food was added in the presence of predators (predator effect alone).
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