陈虎平：GRE阅读真题解析（黄蜂）

　　Immediately relevant to game theory are the sex ratios in certain parasitic wasp species that have a large excess of females. In these species, fertilized eggs develop into females and unfertilized eggs into males. A female stores sperm and can determine the sex of each egg she lays by fertilizing it or leaving it unfertilized. By Fishers genetic argument that the sex ratio will be favored which maximizes the number of descendants an individual will have and hence the number of gene copies transmitted, it should pay a female to produce equal numbers of sons and daughters. Hamilton, noting that the eggs develop within their hostthe larva of another insectand that the newly emerged adult wasps mate immediately and disperse, offered a remarkably cogent analysis. Since only one female usually lays eggs in a given larva, it would pay her to produce one male only, because this one male could fertilize all his sisters on emergence. Like Fisher, Hamilton looked for an evolutionarily stable strategy, but he went a step further in recognizing that he was looking for a strategy.

　　与博弈理论更为直接相关的是某些寄生性黄蜂种类的性别比例，雌性黄蜂占有绝对的过量。在这些种类的黄蜂身上，受精卵发展成为雌性黄蜂，未受精卵发展成为雄性黄蜂。雌性黄蜂能储存精子，并对她所产的每一个卵，通过使其受精或不让其受精，从而决定其性别。按照菲希尔的论点，生物体所会择取的是那样一种性别比例，那种性别比例能在最大程度上增加一个个体所能拥有的后代数量，并因此能在最大程度上增加所传递到后代身上去的基因复制品的数量，对于雌性黄蜂来说，繁殖同等数量的雄性后代和雌性后代仍不乏益处。汉密尔顿注意到，蜂卵是在其寄主另一只昆虫的幼虫体内成熟发展的，并且刚刚自卵中育出的成年黄蜂随即进行交配，然后积各奔东西，提供了一种极为严谨的分析。既然一般而言只有一只雌性黄蜂在一特定的幼虫体内产卵，对她来说，只需要繁殖一只雄性黄蜂便获益匪浅，因为这一只雄性黄蜂可以将其同胞的雌性黄蜂在自卵中育出之际皆予授精。如同菲希尔一样，汉密尔顿也意欲寻觅一种在生物进化上的稳定策略，但他更深入了一步，因为他认识到他的研究正是为了去寻找一种生物体的进化策略。

　　现象解释型

　　TS 首句，两个解释，前负后正。作者支持H

　　结构：

　　1 TS

　　2 x

　　3 y

　　4 kw1

　　5 kw2

　　6 a

　　7 cs

　　生词：

　　parasitic 寄生

　　excess 过度的; 额外的

　　sperm 精子

　　genetic 遗传的

　　mate 交配

　　immediately 立刻, 立即

　　disperse 分散, 散开, 传播

　　emerged 浮现, 脱出

　　cogent 使人信服的

　　strategy 策略

　　conducted 引导, 管理, 带领

　　sought寻求, 探索

　　manipulate 操纵, 操作

　　thereby 因此

　　extinction 绝种

　　1. The author suggests that the work of Fisher and Hamilton was similar in that both scientists

　　 conducted their research at approximately the same time

　　 sought to manipulate the sex ratios of some of the animals they studied

　　 sought an explanation of why certain sex ratios exist and remain stable

　　 studied game theory, thereby providing important groundwork for the later development of strategy theory

　　 studied reproduction in the same animal species

　　Like Fisher, Hamilton looked for an evolutionarily stable strategy, but he went a step further in recognizing that he was looking for a strategy.

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

　　2. The passage contains information that would answer which of the following questions about wasps?

　　A How many eggs does the female wasp usually lay in a single host larva?

　　B Can some species of wasp determine sex ratios among their offspring?

　　C What is the approximate sex ratio among the offspring of parasitic wasps?

　　A female stores sperm and can determine the sex of each egg she lays by fertilizing it or leaving it unfertilized.

　　3. Which of the following is NOT true of the species of parasitic wasps discussed in the passage?

　　 Adult female wasps are capable of storing sperm.

　　 Female wasps lay their eggs in the larvae of other insects.

　　 The adult female wasp can be fertilized by a male that was hatched in the same larva as herself.

　　 So few male wasps are produced that extinction is almost certain.

　　 Male wasps do not emerge from their hosts until they reach sexual maturity.

　　A female stores sperm and can determine the sex of each egg she lays by fertilizing it or leaving it unfertilized.

　　Hamilton, noting that the eggs develop within their hostthe larva of another insect

　　Since only one female usually lays eggs in a given larva, it would pay her to produce one male only, because this one male could fertilize all his sisters on emergence.

　　and that the newly emerged adult wasps mate immediately and disperse, offered a remarkably cogent analysis