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Questions and Answers
What is the primary genetic disadvantage for a diploid sexual female compared to a diploid asexual female in terms of gene transmission to offspring?
What is the primary genetic disadvantage for a diploid sexual female compared to a diploid asexual female in terms of gene transmission to offspring?
- Asexual females require two parents to reproduce, diluting their genetic contribution.
- Sexual females are more prone to genetic mutations during reproduction.
- Sexual females only pass on half of their genetic material to each offspring, whereas asexual females pass on all of their genetic material. (correct)
- Sexual females produce diploid offspring, while asexual females produce haploid offspring.
According to Maynard Smith's model, why does the proportion of asexual females increase in a population also containing sexual individuals?
According to Maynard Smith's model, why does the proportion of asexual females increase in a population also containing sexual individuals?
- Sexual reproduction is more energetically costly, reducing the reproductive output of sexual females.
- Asexual reproduction avoids the 'cost of producing males,' allowing for a higher proportion of reproductive individuals in the population. (correct)
- Asexual females are inherently more fertile and produce more offspring per reproductive cycle.
- Asexual reproduction leads to greater genetic diversity, making asexual populations more adaptable and faster growing.
In Maynard Smith's 'twofold cost of sex' model, if a population starts with a small proportion of asexual females, how does their proportion change in the next generation, assuming all females produce the same number of offspring?
In Maynard Smith's 'twofold cost of sex' model, if a population starts with a small proportion of asexual females, how does their proportion change in the next generation, assuming all females produce the same number of offspring?
- The proportion of asexual females will fluctuate randomly depending on environmental conditions.
- The proportion of asexual females will decrease due to competition with sexual individuals.
- The proportion of asexual females will approximately double in the next generation. (correct)
- The proportion of asexual females will remain constant as both types have equal reproductive success.
The 'twofold cost of sex' is fundamentally a consequence of which biological phenomenon?
The 'twofold cost of sex' is fundamentally a consequence of which biological phenomenon?
Why is the 'twofold cost of sex' sometimes referred to as the 'cost of males'?
Why is the 'twofold cost of sex' sometimes referred to as the 'cost of males'?
In contrast to anisogamy, how does isogamy affect the 'twofold cost of sex'?
In contrast to anisogamy, how does isogamy affect the 'twofold cost of sex'?
Curt Lively's experiments with Potamopyrgus antipodarum snails provided empirical evidence for which concept?
Curt Lively's experiments with Potamopyrgus antipodarum snails provided empirical evidence for which concept?
What is a 'favorable gene combination' in the context of the costs of sexual reproduction?
What is a 'favorable gene combination' in the context of the costs of sexual reproduction?
How does recombination during sexual reproduction potentially pose a 'cost' in terms of favorable gene combinations?
How does recombination during sexual reproduction potentially pose a 'cost' in terms of favorable gene combinations?
Which of the following is NOT described in the text as an additional cost associated with sexual reproduction, beyond the twofold cost of sex and disruption of gene combinations?
Which of the following is NOT described in the text as an additional cost associated with sexual reproduction, beyond the twofold cost of sex and disruption of gene combinations?
Why is searching for mates considered a cost of sexual reproduction?
Why is searching for mates considered a cost of sexual reproduction?
How does courtship behavior contribute to the costs of sexual reproduction?
How does courtship behavior contribute to the costs of sexual reproduction?
Increased susceptibility to predation is a potential cost of sexual reproduction because:
Increased susceptibility to predation is a potential cost of sexual reproduction because:
What is the relationship between sexual reproduction and parasite transmission?
What is the relationship between sexual reproduction and parasite transmission?
Considering the various costs of sexual reproduction, what is the central challenge for evolutionary biologists?
Considering the various costs of sexual reproduction, what is the central challenge for evolutionary biologists?
Which of the following best summarizes the 'demographic' aspect of the twofold cost of sex?
Which of the following best summarizes the 'demographic' aspect of the twofold cost of sex?
In the context of the twofold cost of sex, if both sexual and asexual females produce 'k' offspring, what is the key difference in how these offspring contribute to population growth in the next generation?
In the context of the twofold cost of sex, if both sexual and asexual females produce 'k' offspring, what is the key difference in how these offspring contribute to population growth in the next generation?
Consider a scenario where a mutation arises in a sexual population, leading to a single asexual female. Assuming this asexual female and sexual females produce the same number of offspring, what would be the long-term trend in the proportion of asexual individuals, based on the twofold cost of sex?
Consider a scenario where a mutation arises in a sexual population, leading to a single asexual female. Assuming this asexual female and sexual females produce the same number of offspring, what would be the long-term trend in the proportion of asexual individuals, based on the twofold cost of sex?
Which of the following accurately describes the gamete production in anisogamous sexual reproduction?
Which of the following accurately describes the gamete production in anisogamous sexual reproduction?
In isogamous reproduction, how does gamete fusion differ from anisogamous reproduction in terms of offspring biomass?
In isogamous reproduction, how does gamete fusion differ from anisogamous reproduction in terms of offspring biomass?
What is the primary implication of isogamy for the twofold cost of sex?
What is the primary implication of isogamy for the twofold cost of sex?
The experimental setup in Lively's snail study involved creating populations with a mix of sexual and asexual individuals. What was the key measurement used to assess the competitive outcome between these reproductive modes?
The experimental setup in Lively's snail study involved creating populations with a mix of sexual and asexual individuals. What was the key measurement used to assess the competitive outcome between these reproductive modes?
In Lively's snail experiment, the frequency of asexual snails increased from 35% to 62% in one year. What does this result suggest about the relative fitness of asexual versus sexual snails in that environment?
In Lively's snail experiment, the frequency of asexual snails increased from 35% to 62% in one year. What does this result suggest about the relative fitness of asexual versus sexual snails in that environment?
Consider a two-locus system where alleles 'A' and 'B' together provide a fitness advantage (AB haplotype). How can sexual reproduction with recombination be disadvantageous in this scenario?
Consider a two-locus system where alleles 'A' and 'B' together provide a fitness advantage (AB haplotype). How can sexual reproduction with recombination be disadvantageous in this scenario?
Which of the following is an example of a cost associated with mate searching in sexual reproduction?
Which of the following is an example of a cost associated with mate searching in sexual reproduction?
How might courtship rituals increase the risk of predation for sexually reproducing organisms?
How might courtship rituals increase the risk of predation for sexually reproducing organisms?
Sexually transmitted diseases (STDs) are a direct consequence of which cost of sexual reproduction?
Sexually transmitted diseases (STDs) are a direct consequence of which cost of sexual reproduction?
Considering the 'other costs of sex' (mate searching, courtship, predation risk, parasite transmission), what is a common theme connecting these costs?
Considering the 'other costs of sex' (mate searching, courtship, predation risk, parasite transmission), what is a common theme connecting these costs?
Which reproductive mode faces the 'cost of producing males' as described by Maynard Smith?
Which reproductive mode faces the 'cost of producing males' as described by Maynard Smith?
If a population is constrained by the amount of resources parents can invest in gamete biomass, which reproductive strategy would maximize population growth rate?
If a population is constrained by the amount of resources parents can invest in gamete biomass, which reproductive strategy would maximize population growth rate?
Flashcards
Genetic Cost of Sexual Reproduction
Genetic Cost of Sexual Reproduction
Diploid sexual females produce haploid gametes containing only one set of chromosomes, passing on only half of their genes to offspring. Asexual females pass on twice as many genes.
Twofold Cost of Sex
Twofold Cost of Sex
A population with asexual females grows at twice the rate of a sexually reproducing population because males don't directly produce offspring.
Cost of Anisogamy
Cost of Anisogamy
The twofold cost of sex arises from the production of different sized gametes. Females invest more in biomass and males invest less. This results in slower population growth for sexual reproducers.
Isogamy
Isogamy
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Disruption of Favorable Gene Combinations
Disruption of Favorable Gene Combinations
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Additional Costs of Sexual Reproduction
Additional Costs of Sexual Reproduction
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Study Notes
Costs of Sexual Reproduction
- Sexual reproduction is common among eukaryotes, despite having significant costs.
- Diploid sexual females produce haploid gametes, passing only one set of chromosomes to offspring.
- Asexual females pass on twice as many copies of their genes compared to sexual females, being twice as genetically related to their offspring (assuming no inbreeding).
The Twofold Cost of Sex
- Evolutionary biologist John Maynard Smith argued that asexuals should grow at twice the rate of sexual reproducers.
- Males only inseminate females and do not produce offspring directly.
- Asexual females avoid the "cost of producing males" by producing only females, which do not need insemination.
- The number of asexuals in a population should grow at twice the rate of sexual reproducers.
- The proportion of asexual females approximately doubles each generation when rare in a mostly sexual population.
- The twofold cost of sex is a consequence of anisogamy (production of different gametes), not sex itself.
- Anisogamy sees females produce large gametes with sufficient biomass to develop into adults.
- Males produce millions of tiny sperm, passing genes but little biomass, with most sperm wasted.
- In asexual reproduction, all individuals are female, investing reproductive effort in offspring biomass.
- In isogamy (one type of gamete), each parent produces midsized gametes that fuse, resulting in the same offspring number as asexual reproduction, and avoiding the twofold cost.
- With anisogamy, males invest in sperm (most of which are wasted) rather than biomass that goes into offspring.
- The twofold cost of sex is sometimes called the "cost of males."
- Experiments with Potamopyrgus antipodarum, a snail species, showed that the proportion of asexual females increased in mixed populations of asexual and sexual individuals, supporting the twofold cost of sex.
- In one experiment, the frequency of asexuals rose from 35% to 62% in a single year.
- A repeated experiment found asexuals increased from 29% to 44.6% on average.
Sex Can Break Up Favorable Gene Combinations
- Recombination can break up gene combinations favored by natural selection.
- A favorable gene combination means an allele at one location is favored when with a specific allele at another.
- Recombination breaks up combinations and produces disfavored haplotypes.
Other Costs of Sex
- The search for potential mates requires time and energy.
- Courting potential mates takes time and energy.
- Individuals searching for mates are often less vigilant for predators.
- Individuals may become infected with parasites from mates during courtship, copulation, or as gametes travel through the reproductive tract.
- Many sexually transmitted diseases (STDs) are caused by viruses, bacteria, protozoa, fungi, and arthropods.
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