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Questions and Answers
In species where females have higher parental investment per offspring compared to males, what is the likely outcome regarding mate choice and variance in reproductive success?
In species where females have higher parental investment per offspring compared to males, what is the likely outcome regarding mate choice and variance in reproductive success?
- Females are more choosy, leading to lower variance in reproductive success. (correct)
- Females are less choosy, leading to higher variance in reproductive success.
- Both sexes exhibit equal choosiness with no difference in reproductive success variance.
- Males are more choosy, leading to lower variance in reproductive success.
Which of the following best describes sexual selection?
Which of the following best describes sexual selection?
- The movement of genes from one population to another.
- Random changes in allele frequencies within a population due to chance events.
- Differential reproduction due to variation in the ability to obtain successful matings. (correct)
- Differential survival and reproduction due to traits that enhance survival in a habitat.
Why might sexual selection favor traits that reduce survivorship?
Why might sexual selection favor traits that reduce survivorship?
- Traits can reduce survivorship but can result in more successful mating, offsetting the reduction in survivorship. (correct)
- There is no known instance of preference for traits that reduce survivorship.
- Traits that reduce survivorship always indicate underlying genetic weaknesses which females avoid.
- Sexual selection only favors traits that enhance both mating success and survivorship equally.
What is the primary focus of direct selection for female preference?
What is the primary focus of direct selection for female preference?
Which of the following is an example of a resource a female might acquire through direct selection when choosing a mate?
Which of the following is an example of a resource a female might acquire through direct selection when choosing a mate?
In indirect selection, what primarily influences the selection of a male trait?
In indirect selection, what primarily influences the selection of a male trait?
In the context of genetic correlation, how does a specific allele at one locus (e.g., for a male trait) become correlated with a specific allele at another locus (e.g., for female preference)?
In the context of genetic correlation, how does a specific allele at one locus (e.g., for a male trait) become correlated with a specific allele at another locus (e.g., for female preference)?
What is the key characteristic of the 'good genes' model in sexual selection?
What is the key characteristic of the 'good genes' model in sexual selection?
How does the Fisherian runaway model differ from the 'good genes' model?
How does the Fisherian runaway model differ from the 'good genes' model?
How do 'sexy sons' relate to Fisher’s runaway model?
How do 'sexy sons' relate to Fisher’s runaway model?
Flashcards
Sexual Selection
Sexual Selection
Differential reproduction due to variation in the ability to obtain successful matings.
Natural Selection
Natural Selection
Differential survival/reproduction due to variation in a heritable trait.
Male-male competition
Male-male competition
Direct competition; sperm competition; infanticide committed by males
Direct selection for female preference
Direct selection for female preference
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Indirect selection for preference
Indirect selection for preference
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Genetic correlation (in sexual selection)
Genetic correlation (in sexual selection)
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Fisherian runaway model
Fisherian runaway model
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Good genes model
Good genes model
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Male-male competition
Male-male competition
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Female choice
Female choice
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Study Notes
Parental Investment and Sexual Selection
- There is an original inequality in gametes and parental investment.
- Females and males use alternate strategies to invest in reproductive effort versus mating effort.
- Reproductive effort per offspring is generally higher in females across all sexually-reproducing species, with exceptions in species exhibiting sex-role reversal.
Parental Investment and Variance in Reproductive Success
- Male-male competition (intra-sexual selection) occurs when the sex with lower parental investment per offspring shows greater mating effort and higher variance in lifetime reproductive success.
- Female choice (inter-sexual selection) occurs when the sex with greater parental investment per offspring can be more selective in mate acquisition.
- This is because it limits the mating options of the other sex and results in lower variance in lifetime reproductive success compared to the sex with lower parental investment (typically males).
Sexual Selection
- Sexual selection is differential reproduction due to variation in the ability to obtain successful matings and/or mates of a certain kind/quality.
- Natural selection is differential survival/reproduction due to variation in a heritable trait.
- Sexual selection can produce traits that reduce survivorship, but the critical role of sexually-selected traits in mating success offsets the reduction in survivorship.
Male-Male Competition
- Includes:
- direct competition
- sperm competition
- infanticide committed by males
Female Choice
- Direct selection for female preference occurs when female preference affects female survival or fecundity.
- Fecundity refers to the parental ability to produce offspring, measured in the number of offspring.
- Females choose mates who provide critical resources such as good territory, protection, prenuptial gifts, help with care for offspring, or disease-free status.
- Indirect selection for preference occurs when the female preference does not affect female survival/fecundity, but the preference becomes genetically correlated with the male trait under sexual selection.
- The male trait is favored by selection because it is chosen by females which selects for female preference genes.
- Genetic correlation involves specific alleles at one locus becoming correlated with specific alleles at another locus in the genomes of offspring, resulting from parental mating preferences.
- Female preference and male trait co-evolve due to this genetic correlation.
- Models exist for indirect selection for female preference:
- Fisherian runaway model
- good genes model
- Fisherian runaway model includes female-preference genes and male-trait genes which are genetically correlated.
- Females expressing genetic preference have sons with the preferred trait ("sexy sons").
- Good genes model includes female-preference genes which become genetically correlated with both male-trait genes and good genes.
- Good genes of male mates are passed on to both daughters and sons, enhancing their fitnesses.
- The male trait acts as an indicator of the presence of good genes carried by a particular male mate.
- Indicators of good genes may include bright coloration, exhausting courtship displays, or bilaterally symmetrical traits.
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