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The evolution of sex ratios has produced, in most plants and animals

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The evolution of sex ratios has produced, in most plants and animals  [#permalink]

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New post Updated on: 13 Sep 2019, 03:34
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The evolution of sex ratios has produced, in most plants and animals with separate sexes, approximately equal numbers of males and females. Why should this be so? Two main kinds of answers have been offered. One is couched 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 opposite sex. This is essentially a “group selection” argument. The other, and in my view correct, type of answer was first put forward by Fisher in 1930. This “genetic” argument starts from the assumption that genes can influence the relative numbers of male and female offspring produced by an individual carrying the genes. That sex ratio will be favored which maximizes the number of descendants an individual will have and hence the number of gene copies transmitted. Suppose that the population consisted mostly of females: then an individual who produced sons only would have more grandchildren. In contrast, if the population consisted mostly of males, it would pay to have daughters. If, however, the population consisted of equal numbers of males and females, sons and daughters would be equally valuable. Thus a one-to-one sex ratio is the only stable ratio; it is an “evolutionary stable strategy.” Although Fisher wrote before the mathematical theory of games had been developed, his theory incorporates the essential feature of a game—that the best strategy to adopt depends on what others are doing.

Since Fisher’s time, it has been realized that genes can sometimes influence the chromosome or gamete in which they find themselves so that the gamete will be more likely to participate in fertilization. If such a gene occurs on a sex-determining (X or Y) chromosome, then highly aberrant sex ratios can occur. But more 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 Fisher’s argument, it should still pay a female to produce equal numbers of sons and daughters. Hamilton, noting that the eggs develop within their host—the larva of another insect—and 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 evolutionary stable strategy, but he went a step further in recognizing that he was looking for a strategy.

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

(A) conducted their research at approximately the same time
(B) sought to manipulate the sex ratios of some of the animals they studied
(C) sought an explanation of why certain sex ratios exist and remain stable
(D) studied game theory, thereby providing important groundwork for the later development of strategy theory
(E) studied reproduction in the same animal species


It can be inferred from the passage that the mathematical theory of games has been

(A) developed by scientists with an interest in genetics
(B) adopted by Hamilton in his research
(C) helpful in explaining how genes can sometimes influence gametes
(D) based on animals studies conducted prior to 1930
(E) useful in explaining some biological phenomena


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Originally posted by gmat1393 on 22 Aug 2018, 03:49.
Last edited by SajjadAhmad on 13 Sep 2019, 03:34, edited 1 time in total.
Updated - Complete topic (538).
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Re: The evolution of sex ratios has produced, in most plants and animals  [#permalink]

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New post 25 Oct 2018, 06:39
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1.The author suggests that the work of Fisher and Hamilton was similar in that both scientists

(A) conducted their research at approximately the same time
Crossed out.
We only have one specific year - 1930, and nothing else.
Moreover, this statement, 'Since Fisher’s time, it has been realized that genes can sometimes...', implies that some time has passed between the discussion offered in the second paragraph and the explanation offered by Fisher (in the first paragraph).

(B) sought to manipulate the sex ratios of some of the animals they studied
Crossed out.
New information.
Nothing of the sort is mentioned in the passage.

(C) sought an explanation of why certain sex ratios exist and remain stable
YES
And that's what the passage is all about - a discussion of the evolution of sex ratios, and the explanations of two people in particular.

(D) studied game theory, thereby providing important groundwork for the later development of strategy theory
Crossed out.
New information.
(and game theory itself isn't even the primary focus of the passage)

(E) studied reproduction in the same animal species
Crossed out.
New information.
Nothing of the sort is mentioned in the passage.

*****

It can be inferred from the passage that the mathematical theory of games has been

(A) developed by scientists with an interest in genetics
Crossed out.
New information.
Nothing of the sort is mentioned in the passage.

(B) adopted by Hamilton in his research
Crossed out.
Bait choice.
It's mentioned that "he went a step further in recognizing that he was looking for a strategy", but looking for a strategy DOES NOT NECESSARILY mean that "the mathematical theory of games has been adopted by Hamilton in his research".
Strategies are a part of Game Theory, not GT itself.
The choice is trying to create that information in your head (and thus tricking you into choosing it) when the actual, precise information is nowhere in the passage.

(C) helpful in explaining how genes can sometimes influence gametes
Crossed out.
I see that this is the second most opted choice.
But it's wrong.
In the third sentence of the second paragraph, "But more immediately relevant to game theory..." implies that the idea that "genes can sometimes influence the chromosome or gamete" is also relevant to game theory.
"More immediately relevant" means that the theory can be more readily applied to the latter subject (large excess of females in parasitic wasps), and it means nothing more.
'Readiness of application' DOES NOT equal to the 'application' itself.
If activity X CAN be applied to stuff Z, and that's all what has been said, then then doesn't necessarily mean that activity X HAS been applied to stuff Z.
By choosing C, you're saying that 'the mathematical theory of games has been helpful in explaining how genes can sometimes influence gametes'. That implies APPLICATION. But only the 'readiness of application' is stated in the passage, not the (information about) any application itself!

(D) based on animals studies conducted prior to 1930
Crossed out.
New information.
Nothing of the sort is mentioned in the passage.
(Even contradicts the given information - Fisher's explanation was given in 1930, "before the mathematical theory of games had been developed")

(E) useful in explaining some biological phenomena
YES
You could either get here by reduction, or by pushing more analysis into the choices.
From all that's been said in the passage, this is the ONLY choice that fits.
We can safely say that "the mathematical theory of games has been useful in explaining some biological phenomena".

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Re: The evolution of sex ratios has produced, in most plants and animals  [#permalink]

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New post 19 Nov 2018, 06:45
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1.The author suggests that the work of Fisher and Hamilton was similar in that both scientists

(A) conducted their research at approximately the same time - Incorrect - Fisher put forward 2nd view in 1930.
Although no time explicitly has been mentioned for Hamilton, we can infer that sometime has been passed since Fisher's research because of"Since Fisher’s time, it has been realized that genes can "
(B) sought to manipulate the sex ratios of some of the animals they studied - Incorrect - Nowhere has manipulation been discussed.
(C) sought an explanation of why certain sex ratios exist and remain stable - Correct - a one-to-one sex ratio is the only stable ratio; it is an “evolutionary stable strategy
(D) studied game theory, thereby providing important groundwork for the later development of strategy theory - Incorrect
(E) studied reproduction in the same animal species - Incorrect


2. It can be inferred from the passage that the mathematical theory of games has been

(A) developed by scientists with an interest in genetics - Out of scope - The passage DOES NOT mention who develops the game theory
(B) adopted by Hamilton in his research - ISWAT- Like Fisher, Hamilton looked for an evolutionary stable strategy, but he went a step further in recognizing that he was looking for a strategy.
Based on this we CANNOT infer that Hamilton adopted game theory in research.
(C) helpful in explaining how genes can sometimes influence gametes - Irrelevant - Since Fisher’s time, it has been realized that genes can sometimes influence the chromosome or gamete in which they find themselves so that the gamete will be more likely to participate in fertilization. If such a gene occurs on a sex-determining (X or Y) chromosome, then highly aberrant sex ratios can occur.
(D) based on animals studies conducted prior to 1930 - Incorrect - The other, and in my view correct, type of answer was first put forward by Fisher in 1930. This “genetic” argument starts from the assumption that genes can influence the relative numbers of male and female offspring produced by an individual carrying the genes.
Fisher developed the 2nd view but nowhere in the passage is it mentioned that game theory is based on Fisher's research
(E) useful in explaining some biological phenomena - Correct

Although Fisher wrote before the mathematical theory of games had been developed, his theory incorporates the essential feature of a game—that the best strategy to adopt depends on what others are doing.

But more immediately relevant to game theory are the sex ratios in certain parasitic wasp species that have a large excess of females.

Answer E
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Re: The evolution of sex ratios has produced, in most plants and animals  [#permalink]

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New post 19 Nov 2018, 07:03
Skywalker18 wrote:
1.The author suggests that the work of Fisher and Hamilton was similar in that both scientists

(A) conducted their research at approximately the same time - Incorrect - Fisher put forward 2nd view in 1930.
Although no time explicitly has been mentioned for Hamilton, we can infer that sometime has been passed since Fisher's research because of"Since Fisher’s time, it has been realized that genes can "
(B) sought to manipulate the sex ratios of some of the animals they studied - Incorrect - Nowhere has manipulation been discussed.
(C) sought an explanation of why certain sex ratios exist and remain stable - Correct - a one-to-one sex ratio is the only stable ratio; it is an “evolutionary stable strategy
(D) studied game theory, thereby providing important groundwork for the later development of strategy theory - Incorrect
(E) studied reproduction in the same animal species - Incorrect


2. It can be inferred from the passage that the mathematical theory of games has been

(A) developed by scientists with an interest in genetics - Out of scope - The passage DOES NOT mention who develops the game theory
(B) adopted by Hamilton in his research - ISWAT- Like Fisher, Hamilton looked for an evolutionary stable strategy, but he went a step further in recognizing that he was looking for a strategy.
Based on this we CANNOT infer that Hamilton adopted game theory in research.
(C) helpful in explaining how genes can sometimes influence gametes - Irrelevant - Since Fisher’s time, it has been realized that genes can sometimes influence the chromosome or gamete in which they find themselves so that the gamete will be more likely to participate in fertilization. If such a gene occurs on a sex-determining (X or Y) chromosome, then highly aberrant sex ratios can occur.
(D) based on animals studies conducted prior to 1930 - Incorrect - The other, and in my view correct, type of answer was first put forward by Fisher in 1930. This “genetic” argument starts from the assumption that genes can influence the relative numbers of male and female offspring produced by an individual carrying the genes.
Fisher developed the 2nd view but nowhere in the passage is it mentioned that game theory is based on Fisher's research
(E) useful in explaining some biological phenomena - Correct

Although Fisher wrote before the mathematical theory of games had been developed, his theory incorporates the essential feature of a game—that the best strategy to adopt depends on what others are doing.

But more immediately relevant to game theory are the sex ratios in certain parasitic wasp species that have a large excess of females.

Answer E

For question 2, C is irrelevant because it is not explaining how genes influence gametes. Rather , per the exceprt,

But more immediately relevant to game theory are the sex ratios in certain parasitic wasp species that have a large excess of females.


we can be sure of the game theory's applicability to the wasps aberrantly high sex ratio. In short, just an example of applicabilty of game theory has been stated and this is irrelevant to the explanation.

Please point out flaw in my reasoning, if any.


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Re: The evolution of sex ratios has produced, in most plants and animals   [#permalink] 19 Nov 2018, 07:03
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