Sexual Selection Flashcards Preview

GeoSci 110 (Exam 2) > Sexual Selection > Flashcards

Flashcards in Sexual Selection Deck (14):

Sexual Dimorphism

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


Mate Choices

"power to charm females"

- i.e. peacocks and their feathers


Intra-Sexual Selection

"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)


Reproductive Potential

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


Causes of sex role reversals (migratory shorebirds and polyandrous females)

migratory shorebird females experience high levels of stress;

- if the female is malnourished then she has low egg production and the eggs she produces will be low in quality resulting in weak chicks

- solution? male birds stay at home to prevent weak offspring end result!