Lecture 8 Flashcards
What defines sex?
The gametes an organism produces
What is sexual dimorphism
Differences in males and females of a species
Primary sexual traits
Traits related to gonads and genitalia
Secondary sexual traits
Not essential for reproduction (used to gain matings)
Darwin noted about secondary sexual traits
- Sexually dimorphic
- Usually in mating season
- Not found in juveniles or the other sex
What was Darwin’s theory of sexual selection?
Selection caused by competition for mates between individuals of the same sex
Why are males usually sexually selected?
They can increase fitness by mating multiple times
What is sex role reversal?
Exception to rule that usually males are sexually selected and not females
Examples of sex role reversal
- Seahorses
- Painted snipe (bird)
Characteristics of sex role reversal
Females can increase fitness by mating with more males, males cannot increase fitness this way, males give parental care
Types of Male-Male competition
- Combat
- Sperm Competition
- Infanticide
What is an example of male-male combat?
Elephant seals (large body correlates with reproductive success)
What is an example of sperm competition?
Penis of damselflies adapted for removing sperm of other males from female reproductive tract
What is an example of infanticide?
After taking over a pride male will kill other male’s cubs to make females more receptive to mating
What is mating preference?
Anything that biases what kind of male a female will mate with, usually innate
What are two features of male traits sexually selected by female choice, with examples?
- Can decrease survival, Tungara frogs vocalization
- Increase mating success, Widowbird tail length
What is lifetime fitness?
A compromise between maximizing survival and maximizing mating success
3 reasons female preference for extreme male displays evolved
- Natural selection acting of preferences
- Pleiotropic effects
- Evolution of preferences for “good genes”
(T/F) Males that give paternal care will have big displays and not be well camouflaged
False
What is a nuptial gift?
Food/gift provided during mating
What is an example of a nuptial gift?
Sicklebilled vanga
What is an example of pleiotropic preference genes?
Male Splitfin fishes yellow stripe on tails may look like prey to females
What is the hypothesis of the preference for good genes?
Displays are correlated with good genes (good immune system and foraging), enhance offspring survival, genes for displays spread
What is an experiment of the “good genes” hypothesis?
Stickleback fishes, redder males have offspring that have better immune system and less likely to be parasitized
