Sexual Selection Flashcards
What are sexually dimorphic traits?
Why do sexually dimorphic traits require a special evolutionary explanation? In which sex are elaborate dimorphic traits usually found?
What is sexual selection? Explain its relationship to natural selection. How is it similar,
and how is it different?
*What is anisogamy?
Anisogamy = idea that refers to males and females having unequal-sized gametes.
What predictions does anisogamy make about male vs. female limitations on fitness? What does it predict about male vs. female strategies for increasing fitness?
*What is Trivers’ Parental Investment Theory?
A theory that expanded anisogamy theory to include ALL investment in offspring and takes parental care into account.
How is Trivers’ Parental Investment Theory similar/different to anisogamy theory? How does it affect the predictions about anisogamy and male vs female limitations on fitness?
*What is Bateman’s Principle (3 parts)? Where does each prediction come from?
1 & 2) Variation in male reproductive success and mating success is higher than variation in female RS and MS.
- also called a reproductive skew
3) Males have an increasing number of mates and an increasing number of RS. Females have an increasing number of mates does not increase RS.
How do we measure the strength of sexual selection? In what circumstances would we
expect a population to be experiencing very strong sexual selection? Very weak sexual
selection? How does this relate to the degree of sexual dimorphism we would expect?
*Contrast intra- and inter-sexual selection.
Intrasexual selection = sexual selection happening within one sex
Intersexual selection = sexual selection that imposes selection on the other sex.
How might intra- and inter- sexual selection lead to sexual dimorphism in different traits? How might each of them lead to elaborate traits that come
at a cost if we consider natural selection alone?
*Describe and give an example of pre-copulatory sexual selection for both intra- and intersexual selection.
Pre-copulatory sexual selection = sexual selection that occurs prior to the act of copulation
*Describe and give an example of copulatory sexual selection for both intra- and intersexual selection.
Copulatory sexual selection = sexual selection that occurs prior to the act of copulation
*Describe and give an example of post-copulatory sexual selection for both intra- and intersexual selection.
Post-copulatory sexual selection = sexual selection that occurs after copulation has occurred.
What are sexual role-reversed species? Describe the roles of inter- vs. intra-sexual
selection in these species. What makes these species different than more “typical”
species (i.e. how/why would a species evolve role-reversal in the first place?)
*What is meant by “alternative mating tactics”? How can multiple strategies persist in a
population?
Alternative mating strategies = distinct male mating tactics, usually associated with different morphologies.
Multiple strategies persist in a population because they need to be equal
*What are the differences between flexible, fixed conditional, and genetic tactics?
“Flexible alternative mating strategies” = where an individual male can pursue more than one strategy.
“Fixed alternative mating strategies” = where one male will only use one strategy.
“Genetically determined” = gene that give an assigned strategy to a male
Why are females choosy? What types of benefits can females get from having a preference?
What are the various explanations for why females might prefer particular males
over others? For each, what predictions can we make about the males that are preferred
vs. those that are not preferred? What predictions can we make about the resulting
offspring?
Explain the steps in Fisher’s hypothesis of Runaway Sexual Selection.
What is sexual conflict? Why does it occur?
*What are direct benefits?
Benefits that increase the offspring quantity
*What are indirect benefits?
Benefits that increase offspring quality
