※ 引述《prompter (Qu)》之铭言：
: TPO阅读第一篇
: Speciation in Geographically Isolated Populations
: 第六题
: 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
国中生物 当时教我们的 这个 是 地理隔离 geographic isolation
两个观念
Geographic isolation是物种形成的起因条件之一 但不是唯一的途径
有地理隔离 也不一定能诞生新的物种
有性生殖生物而言 生殖隔离 定义了 物种 之间的关系
reproductive isolation 另外一种说法是 hybridization barriers
另一方面reproductive isolation 造成的原因 确实包含Geographic isolation
然光是Geographic isolation 如果两个群体分离不够久 或者累积的差异不足以达成
reproductive isolation 或说 hybridization barriers
就不能称这两群为不同物种
: 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
: 但我选D
: 因为原文不是写说冰河退去后，分开的物种又恢复连结
: 但A说Were reproductively isolated even after the glaciers disappeared
: "冰河退去后 物种繁衍被孤立"
: 这样解释不是相反了吗?
这段说了一大堆
其实只是再说 地理隔离 要造成"物种"species
要达成 生殖隔离
Some groups that had descended from the same parent population
were no longer reproductively compatible – they had evolved into separate
species.
对于物种 一个非常粗略的定义是(摘自维基百科)
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.
虽然这句话很多时候是不适用的
例如有些物种不只有两个性别
有些是无性生殖
但是对于有性生殖的生物 物种的简单定义 是要产生 有生育能力的子代
_____________________________________________________________
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
所以地利隔离 只是其中一种起因
隔离之后 两个被分隔的群体各各自演化 产生差异
如果差异最后大到产生了 无法交配 或者交配无法产下健康子代 或子代无生殖能力
(换言之除去冰河之后 两个群体的个体 差异仍大到影响繁殖)
就产生了新的种
否则就只是两个亚种 (仍有生殖能力)
__________________________________________
以前好像是这样教的
地理隔离 与 时间
让两族群累积基因库的差异
导致种群间生殖隔离
物种形成

谢谢