Flashcards in Sexual Selection Deck (14):
differences in morphology between male and female members of a species
- can include physical traits as well as behavioral traits (i.e. birdsongs)
Sexual Dimorphism (male characteristics)
- more brightly colored
- sport various adornments
- larger body size
Why did the sight of a peacock's tail make Darwin feel sick?
- how can a long showy tail be beneficial for the survival of a species?!
- it takes A LOT of metabolic energy to create and the colors make them more attractive to predators
What is sexual selection?
differential success in reproduction
- if the female likes the male with the more colorful feathers, the male produces more offspring and the trait is passed down
Examples of Sexual Selection Processes
1.) Mate Choices
2.) Intra-Sexual Selection
"power to charm females"
- i.e. peacocks and their feathers
"power to conquer other males in battle"
- i.e. elephant seals, deer (bucks)
How does sexual selection perpetuate sexual dimorphism?
- both traits and the preference for it co-evolve
- females choose the males with distinctive traits
- offspring inherit exaggerated trait (males) or the preference for that trait (females)
- selection reinforces both trait and preference
Examples of post-mating competition
males hang around after mating and guard against other male suitors
- fruit flies and their "penis scoop" that can scoop out the sperm of competitors
- dragon flies who attach themselves to the female after sex
- some snakes and rodents have sperm that temporarily block reproductive tract after mating
Factors involved in evolution of typical sex roles (male vs. female)
1.) relative investment in reproduction
2.) Reproductive potential
Relative Investment in Reproduction
usually greater in females (therefore women are more choosey)
usually greater for males (therefore males must be more competitive and aggressive)
Correlation between levels of aggression between males vs. disparity in number of mates
Monogamy vs. Polygamy
- the greater the disparity among males in terms of number of mates results in a greater level of aggression