9. Sexual Selection Flashcards
What is intra-sexual selection?
Favours ability to compete with same sex for fertilisations
Male-male competition
What is inter-sexual selection?
Favours ability to attract opposite sex partners for fertilisation
Female choice
What is anisogamy?
Sexual reproduction by the fusion of dissimilar gametes
What is batemans principle (1948)?
If there is unequal investment in offspring the high investor’s RS is limited by resources and time, the low investor’s RS is limited by number of matings therefore low investors undergo strong sexual selection – competitive ability favoured.
What does batemann’s principle not explain? - Concorde fallacy
Why there is more intense sexual selection for males Parental care (concorde fallacy = cant stop now, invested so much)
What factors influence whether a partner stays or deserts?
Sex ratio and mating opportunities
Polyandry by females - paternity assurance
Internal vs external insemination
Intensity of male-male competition can explain the extent of sexual dimorphism in…
Body size
Weaponry
Testes size
Who found out that fruit flies adjusted the amount of ejaculate depending on the presence of other males?
Gage et al 1991
When can sophisticated sperm allocation occur?
When in the presence of other males
When the females display differing levels of quailty (sexual ornaments)
What is an example or non-genetic or ‘direct’ benefits?
Courting male can provide resources or may signal ability to provide better resources later
What are some examples of genetic of indirect benefits?
Survival of offspring, fitness, disease resistance
Attractiveness (sexy sons)
How can an elaborate trait signal honest viability?
Physical constraints - Dietary carotenoids
Handicap Principle
What is the multiple message hypothesis?
Genetic and direct benefits are not mutually exclusive
Fluctuating selection pressures will maintain a constant level of genetic variation in sexual traits
What is the multiple message hypothesis?
Genetic and direct benefits are not mutually exclusive
Fluctuating selection pressures will maintain a constant level of genetic variation in sexual traits
How do mating conflicts affect the genitalia of certain species?
Pheasant: no conflict over mating so small phallus and short vagina.
Pekin duck: conflict over mating so muscular phallus, vagina ith dead end sacs and clockwise coils
