※ 引述《prompter (Qu)》之銘言：
: TPO閱讀第一篇
: Speciation in Geographically Isolated Populations
: 第六題
: According to paragraph 3, separation of subpopulations by glaciers resulted
: in speciation in those groups of plants and animals that
: A Were reproductively isolated even after the glaciers disappeared
: B Had adjusted to the old conditions caused by the glaciers
: C Were able to survive being separated from their parent population
: D Had experienced some genetic divergences from their parent population
國中生物 當時教我們的 這個 是 地理隔離 geographic isolation
兩個觀念
Geographic isolation是物種形成的起因條件之一 但不是唯一的途徑
有地理隔離 也不一定能誕生新的物種
有性生殖生物而言 生殖隔離 定義了 物種 之間的關係
reproductive isolation 另外一種說法是 hybridization barriers
另一方面reproductive isolation 造成的原因 確實包含Geographic isolation
然光是Geographic isolation 如果兩個群體分離不夠久 或者累積的差異不足以達成
reproductive isolation 或說 hybridization barriers
就不能稱這兩群為不同物種
: 第三段是:
: Geographic isolation can also proceed slowly, over great spans of time. We
: find evidence of such extended events in the fossil record, which affords
: glimpse into the breakup of formerly continuous environments. For example,
: during past ice ages, glaciers advanced down through North America and Europe
: and gradually cut off parts of populations from one another. When the
: glaciers retreated, the separated populations of plants and animals came into
: contact again. Some groups that had descended from the same parent population
: were no longer reproductively compatible – they had evolved into separate
: species. In other groups, however, genetic divergences had not proceeded so
: far, and the descendants could still interbreed – for them, reproductive
: isolation was not completed, and so speciation had not occurred.
: 答案是A
: 但我選D
: 因為原文不是寫說冰河退去後，分開的物種又恢復連結
: 但A說Were reproductively isolated even after the glaciers disappeared
: "冰河退去後 物種繁衍被孤立"
: 這樣解釋不是相反了嗎?
這段說了一大堆
其實只是再說 地理隔離 要造成"物種"species
要達成 生殖隔離
Some groups that had descended from the same parent population
were no longer reproductively compatible – they had evolved into separate
species.
對於物種 一個非常粗略的定義是(摘自維基百科)
A species is often defined as the largest group of organisms in which two
individuals are capable of reproducing fertile offspring,
typically using sexual reproduction.
雖然這句話很多時候是不適用的
例如有些物種不只有兩個性別
有些是無性生殖
但是對於有性生殖的生物 物種的簡單定義 是要產生 有生育能力的子代
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Reproductive Isolation 有很多方法
geographic isolation
ecological isolatino
temporal isolation
behavioral isolation
mechanical isolation
prevention of genome fusion
hybrid inviability or infertility
所以地利隔離 只是其中一種起因
隔離之後 兩個被分隔的群體各各自演化 產生差異
如果差異最後大到產生了 無法交配 或者交配無法產下健康子代 或子代無生殖能力
(換言之除去冰河之後 兩個群體的個體 差異仍大到影響繁殖)
就產生了新的種
否則就只是兩個亞種 (仍有生殖能力)
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以前好像是這樣教的
地理隔離 與 時間
讓兩族群累積基因庫的差異
導致種群間生殖隔離
物種形成