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  3. The evolution of sex ratios has produced, in most plants and animals with separate sexes, approximately equal number of males an

The evolution of sex ratios has produced, in most plants and animals with separate sexes, approximately equal number of males an

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问题     The evolution of sex ratios has produced, in most plants and animals with separate sexes, approximately equal number of males and females. Why should this be so? Two main kinds of answers have been offered. One is【C1】______in terms of advantage to population. It is argued that the sex ratio will evolve so as to maximize the number of meetings between individuals of the【C2】______sex. The other type of answer was first put forward by Fisher in 1930. The "genetic" argument starts from the【C3】______that genes can influence the relative numbers of male and female【C4】______produced by an individual carrying the genes. Suppose that the population consisted mostly of females, it would pay to have sons. In contrast, if the population consisted mostly of males, it would have daughters. If, however, the population consisted of【C5】______numbers of males and females, sons and daughters would be equally valuable. Thus a one-to-one sex ratio is the only【C6】______ratio; it is an "evolutionarily stable strategy". Although Fisher wrote this, before the mathematical theory of games had been developed, his theory【C7】______the essential feature of a game—that the best strategy to adopt depends on what others are doing.
    More immediately relevant to game theory are the sex ratios in certain parasitic wasp(寄生蜂)species that have a large excess of females. In these species, fertilized eggs develop into females and unfertilized eggs into males. A female can determine the sex of each egg she lays by fertilizing it or leaving it unfertilized. By Fisher’s argument, it should still pay a【C8】______to produce equal numbers of sons and daughters. Hamilton, noting that the eggs develop within their host and that the newly emerged adult wasps mate immediately and【C9】______. offered a remarkably reasonable analysis. Like Fisher, Hamilton looked for an【C10】______stable strategy, but he went a step further in recognizing that he was looking for a strategy.
A)female I)predecessor
B)updated J)offspring
C)stable K)disperse
D)incorporates L)couched
E)invariably M)male
F)evolutionarily N)opposite
G)assumption O)homogeneous
H)equal
【C3】
选项
答案G
解析 空前的定冠词the及空后的that从句提示，此处应填一名词。此句中this“genetic”argument即是Fisher的观点。后文解释这一观点的时候大量运用suppose，if等表假设的引导词，说明this“genetic”argument还没有事实证明，只是假设和猜想。assumption符合此意。
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