Sexual selection Flashcards
(22 cards)
When did sexual reproduction first evolve?
About 2 billion years ago in single-celled protists.
What are the costs of sexual reproduction?
Only half of genes are passed, need for mates, risk of disease, energy cost.
What is the Red Queen Hypothesis?
Organisms must constantly adapt and evolve to survive against evolving adversaries (other species).
Why might organisms switch between asexual and sexual reproduction?
In stable environments asexual reproduction dominates; in unstable ones, sexual reproduction increases variation.
What is sexual selection?
Selection for traits that improve reproductive success.
How is sexual selection different from natural selection?
Natural selection improves survival; sexual selection improves mating success.
What are primary sexual characteristics?
Genitalia and reproductive organs.
What are secondary sexual characteristics?
Traits not directly involved in reproduction, like bright plumage or antlers.
What is sexual dimorphism?
Differences in appearance between males and females of a species.
What is intrasexual selection?
Competition among members of one sex for access to mates.
What is intersexual selection?
Choice by one sex of mates from the opposite sex.
What is an example of intrasexual selection?
Male-male competition for mates, such as in deer antler battles.
What are ‘sneaker’ males?
Males that avoid direct competition and sneak matings.
What is sperm competition?
Competition between sperm of different males to fertilize eggs.
What are examples of male traits shaped by female choice?
Peacock tails, elaborate songs, bright plumage.
What is the Good Genes Hypothesis?
Females select mates with superior genes that enhance offspring fitness.
What is the Sexy Son Hypothesis?
Females select mates whose sons will also be attractive to females.
Why can sexual selection oppose natural selection?
Exaggerated traits may reduce survival but increase mating success.
What is an honest signal in sexual selection?
A trait that is costly and thus reliably signals genetic quality.
e.g. big antlers can only be grown by strong and healthy deer
How can female choice lead to alternative male reproductive strategies?
When female preferences favor multiple successful mating strategies.
What is the Handicap Principle?
Costly traits honestly indicate male genetic fitness.
Why is sexual selection sometimes maladaptive?
Because traits favored for mating success can reduce survival (e.g., large antlers).
