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Questions and Answers
In a population of Galápagos finches with bill sizes near the optimum for the island's seeds, what is most likely to occur if the main seed resource disappears and is replaced by plants with much larger seeds?
In a population of Galápagos finches with bill sizes near the optimum for the island's seeds, what is most likely to occur if the main seed resource disappears and is replaced by plants with much larger seeds?
- Correlational selection between seed size and bill size will occur.
- The new plant species will go extinct as finches eat all the seeds.
- Disruptive selection increasing phenotypic variance for bill size.
- Stabilizing selection to maintain the population average bill size.
- Directional selection increasing bill size towards a new optimum. (correct)
Why do three-spined stickleback fish with low-Eda (LL) alleles have a selective advantage compared to fish with high-Eda (CC) alleles in freshwater environments?
Why do three-spined stickleback fish with low-Eda (LL) alleles have a selective advantage compared to fish with high-Eda (CC) alleles in freshwater environments?
- Low-`Eda` fish use their available energy to grow faster and add body mass instead of armor. (correct)
- Low-`Eda` fish allocate more resources to armor development.
- Low-`Eda` fish grow slower, taking longer before developing armor.
- Low-`Eda` fish can grow heavier armor to defend against predators.
Why is describing average patterns in nature distinct from describing every pattern?
Why is describing average patterns in nature distinct from describing every pattern?
- Averages apply to asexual species only.
- Averages summarize overall trends, while individual cases may vary. (correct)
- Averages are theoretical while every pattern is factual.
- Averages include moral properties, but every pattern is amoral.
What genetic consequence primarily results from asexual reproduction over many generations, as described by Muller's ratchet?
What genetic consequence primarily results from asexual reproduction over many generations, as described by Muller's ratchet?
Why can sex be beneficial despite its two-fold cost?
Why can sex be beneficial despite its two-fold cost?
How does the 'Red Queen effect' contribute to the maintenance of sexual reproduction in a population?
How does the 'Red Queen effect' contribute to the maintenance of sexual reproduction in a population?
According to the concept of differential parental investment, how do the reproductive strategies typically differ between males and females?
According to the concept of differential parental investment, how do the reproductive strategies typically differ between males and females?
How does anisogamy relate to the fundamental asymmetry of sex?
How does anisogamy relate to the fundamental asymmetry of sex?
What evolutionary force is most directly responsible for the development of sexual dimorphisms?
What evolutionary force is most directly responsible for the development of sexual dimorphisms?
How could the operational sex ratio (OSR) influence the intensity of sexual selection?
How could the operational sex ratio (OSR) influence the intensity of sexual selection?
In elephant seals, intense sexual selection on males leads to high variance in reproductive success. How is this variance typically manifested?
In elephant seals, intense sexual selection on males leads to high variance in reproductive success. How is this variance typically manifested?
What is the primary difference between direct and indirect benefits in the context of female mate choice?
What is the primary difference between direct and indirect benefits in the context of female mate choice?
In species where males provide spermatophores to females, how does the number of spermatophores eaten influence the females?
In species where males provide spermatophores to females, how does the number of spermatophores eaten influence the females?
How can the concept of 'pre-existing sensory bias' explain the evolution of certain male traits?
How can the concept of 'pre-existing sensory bias' explain the evolution of certain male traits?
Why might mutual courtship displays occur in species such as blue-footed boobies, where both sexes exhibit similar behaviors during courtship?
Why might mutual courtship displays occur in species such as blue-footed boobies, where both sexes exhibit similar behaviors during courtship?
What are the evolutionary consequences when females but not males are the limiting sex?
What are the evolutionary consequences when females but not males are the limiting sex?
How does uncertain paternity affect the parental care behavior of males in certain species?
How does uncertain paternity affect the parental care behavior of males in certain species?
What does the term 'naturalistic fallacy' mean in the context of evolutionary biology?
What does the term 'naturalistic fallacy' mean in the context of evolutionary biology?
Under what conditions should asexual species be more abundant than sexual species, based on reproductive efficiency?
Under what conditions should asexual species be more abundant than sexual species, based on reproductive efficiency?
In Snails, what is the relationship between populations and parasite trematodes?
In Snails, what is the relationship between populations and parasite trematodes?
If large exaggerated traits decrease survival, what kind of selection takes place?
If large exaggerated traits decrease survival, what kind of selection takes place?
What is Darwin's Puzzling Pattern?
What is Darwin's Puzzling Pattern?
What is intersexual selection?
What is intersexual selection?
How does the rate of reproduction relate to operational sex ratio?
How does the rate of reproduction relate to operational sex ratio?
Which sex do Alleles more strongly influence to increase attraction in the general population?
Which sex do Alleles more strongly influence to increase attraction in the general population?
What are armaments and ornaments in the context of sexual selection?
What are armaments and ornaments in the context of sexual selection?
What does fecundity and number of mates limit respectively?
What does fecundity and number of mates limit respectively?
What is the effect of beneficial mutation on hosts and resulting mutations in parasites.
What is the effect of beneficial mutation on hosts and resulting mutations in parasites.
How does direct benefits affect female selection?
How does direct benefits affect female selection?
How do indirect benefits influence offspring?
How do indirect benefits influence offspring?
What is the result of sexual selection stronger on females than males?
What is the result of sexual selection stronger on females than males?
During what time does roles reverse, relative to factors?
During what time does roles reverse, relative to factors?
For parental care, which has uncertain and certain paternity?
For parental care, which has uncertain and certain paternity?
As a result of different selection pressures on males and females, what is maximized?
As a result of different selection pressures on males and females, what is maximized?
In the context of evolutionary biology, what is the 'two-fold cost of sex'?
In the context of evolutionary biology, what is the 'two-fold cost of sex'?
What would result in the need to avoid the naturalistic fallacy?
What would result in the need to avoid the naturalistic fallacy?
Why would three spined stickleback fish favor less armour?
Why would three spined stickleback fish favor less armour?
What is the result of the Red Queen hypothesis in sex?
What is the result of the Red Queen hypothesis in sex?
Flashcards
Asexual reproduction
Asexual reproduction
Asexual reproduction produces daughters that produce more daughters.
Reproduction rates
Reproduction rates
Rate of reproduction is lower in sexual species compared to asexual species.
Muller's ratchet
Muller's ratchet
Accumulation of irreversible, deleterious mutations in asexual populations over generations.
Genetic load
Genetic load
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Deleterious alleles
Deleterious alleles
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Red Queen effect
Red Queen effect
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Darwin's Dilemma
Darwin's Dilemma
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Differential parental investment
Differential parental investment
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Sexual dimorphism
Sexual dimorphism
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Intrasexual selection
Intrasexual selection
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Intersexual selection
Intersexual selection
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Limitations on the sexes
Limitations on the sexes
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Operational sex ratio
Operational sex ratio
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Fundamental asymmetry of sex
Fundamental asymmetry of sex
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Sexual selection
Sexual selection
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Ornaments
Ornaments
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Armaments
Armaments
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Direct benefits
Direct benefits
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Indirect benefits
Indirect benefits
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Study Notes
- Lecture 17 focuses on the Evolution of Sex I, referencing E&Z, Chapter 11
- Average patterns in nature differ from universal patterns
- What "is" across non-human taxa doesn't define what "ought to be" in humans, as per Hume's law
- Natural properties and moral properties are not equivalent; avoid the naturalistic fallacy, as explained by G.E. Moore
Two-Fold Cost of Sex
- Asexual females produce daughters which produce more daughters
- Sexual reproduction necessitates mating with a male
- Half of the offspring from sexual reproduction will be male
- Reproduction rates in sexual species are half that of asexual species
- Asexual species would dominate if offspring production is equal and offspring fitness is equal
Muller's Ratchet
- Genomes of asexual populations accumulate irreversible deleterious mutations over generations
- The ratchet analogy indicates that effects can only turn in one direction
- Genetic load is the build up of deleterious mutations over time
- Deleterious alleles become fixed in asexual populations but are removed from sexual populations
Red Queen Effect and Sexual Reproduction
- The Red Queen effect makes sex beneficial in host/parasite interactions
- Populations that have higher rates of parasitism by trematodes are more sexual
Darwin's Dilemma
- Differential parental investment plays a role
- Puzzling patterns include sexual dimorphism
Types of Sexual Selection
- Intrasexual selection refers to competition
- Intersexual selection refers to mate choice
- The question is posed: Why be choosy?
- Roles reverse when factors reverse
Differences in Investment
- Eggs tend to be larger than sperm
- Females invest more energy in eggs and offspring than males
Limitations on the Sexes
- Females are limited by fecundity
- Males are limited by the number of mates
Uncertain Paternity & Parental Care
- Females have certain paternity
- Males have uncertain paternity
- Resources could go to non-offspring
Sexual Reproduction & Selection
- Sexual reproduction creates different selection pressures on males & females
- Males & females may have strategies for maximizing their lifetime reproductive success (fitness)
- The operational sex ratio (OSR) is the ratio of males:females capable of reproducing at a certain time
- Slower reproduction in females leads to male-biased OSR
Fundamental Asymmetry of Sex
- Females should be choosy about mates because of anisogamy and offspring care
- The opposite may be true for males
- Males compete for mates
- Alleles that increase male attractiveness or the ability to compete should increase in a population
- Sexual selection acts more strongly on males than on females
Sexual Selection
- Differential reproductive success from competition for mates drives sexual selection
- Intrasexual selection is competition
- Intersexual selection is mate choice or attractiveness
- Sexual selection is commonly stronger on males
- Male-biased OSR enables selection favoring males that outcompete other males for access to females
Sexual Dimorphism
- Ornaments are attractive traits that increase mating success
- Armaments are weaponry used to outcompete other individuals
Sexual Selection in Male Elephant Seals
- Intense sexual selection occurs on male elephant seals, and most males do not sire any offspring
- Males with larger harems have more offspring
- There is a higher variance in reproductive success for makes compared to females
Costs of Competing for Mates
- Competing for mates is costly
- Red deer mortality is much higher for stags compared to hinds
- Mean number of offspring per year is higher in males but only for a few years
Benefits of Female Choice
- Direct benefits benefit the female directly, such as the resources like food, nest sites, or protection
- Indirect benefits affect the genetic quality of the female's offspring
Direct Benefits Example
- A spermatophore that females eat
Indirect Benefits Example
- Choosy females produce choosy daughters & attractive sons
Female Preferences
- Preferences have a genetic component
Sex Investment and Choosiness
- The sex that 'invests' more in reproduction is often the choosy sex
- When females aren't limited, stronger sexual selection may occur in females
- Male dance flies are choosy, females are 'showy'
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