Sexual Selection - 20 Flashcards
Define sexual dimorphism
differences between males and females
Define ecological selection
differential reproduction success due to individual variation in survival and reproductive output
Define sexual selection
differential reproductive success due to individual variation in mating success
Define intrasexual selection
contests between members of the same sex (ex. male-male competition)
Define intersexual selection
selection via mate choice (ex. non-random mate choice by females)
What are 4 asymmetries in sexual reproduction
- parental investment
- limits on reproductive success
- mating systems
- operational sex ratio
Define anisogamy
male and female gametes are different sizes
Bateman’s principle (2)
male reproductive success is limited by access to females and produce many cheap gametes
whereas female reproductive success is limited by access to resources and produce few gametes
what mating systems have the highest and lowest strength of selection
monogamy is lowest
polygyny and polyandry are highest
Is sexual selection more important for males or females and why
males because intrasexual selection includes direct competition, sperm competition, and infanticide
compared to intersexual competition of female choice
Explain sperm competition
either having larger sperm, higher number, copulatory plug, pheromones, special structures (remove any sperm that were already present and then fertilize)
What is infanticide
males often killed unweaned offspring to allow the female to be ready to reproduce again, not to show dominance
What are the direct benefits that come from female choice
females benefit from increased nutrition, provisioning, parental care that increases reproductive output or the quality of their offspring
What are the indirect benefits of female choice
- good genes hypothesis
- sexy sons hypothesis
What is the good genes hypothesis
genetically superior mates produce offspring with higher fitness
What is the sexy sons hypothesis
females mating with preferred fathers produce sons with higher mating success and females with that preference
What are nuptial gifts an example of
direct benefit - male present partner with food, and the bigger the food the longer the duration of copulation and number of sperm transferred
What are examples of direct benefits for females
- nuptial gifts
- female consuming portion of spermatophore
- sexual cannibalism
- adaptive male suicide
What is the likely cause of sexual dimorphism arising
female choice is responsible
Stronger sexual selection on females leads to the expression of….
secondary sexual characters in females and not males
What is Bateman’s gradient and sex-role reversal
in species where males have more potential investment then females, then females are limited by males for reproductive success
Explain how sexual selection differs in plants
sexual selection doesn’t increase due to increased mating, but due to increases in accessibility to pollen
What kind of wind-pollinated species are the most successful
- male flowers have larger reproductive parts and the larger perianth
- female flower has larger reproductive parts and the larger perianth
(based on perianth)