Animal Behavior + Adaptations 2

sexual dimorphism

sex differences

sexual differences: Males

larger, weaponry, aggressive, ornamented, behavioral courtship

sexual differences: Females

smaller, less ornamented, invest more in offspring

traits proliferate if…

they provide a net reproductive advantage

sexual selection

a natural selection process where certain traits increase mating success and therefore reproductive advantage

Intrasexual competition

physical, overt competition

Intersexual competition

Appealing to sexual preferences of other sex

Why do males usually have more sexually selected traits?

They invest less in offspring

Organisms must use resources…

in mutually exclusive ways

More investing sex is a…

more limited reproductive resource

Sex differences in parental investment produce…

sex differences in reproductive rates

fertile members of the (more)-investing sex are…

less common than fertile members of (less)-investing sex

Bateman’s principle

Relationship between males and reproductive success is stronger than it is for females

traits promoting access to sexual partners provide more of a…

reproductive advantage to males than females

Variance in reproductive success will be greater among…

less-investing sex

variance

measure of spread data on a distribution

greater the reward in reproduction…

most likely a costly strategy will spread

More-investing sex tends to be…

picky about who it will mate with

Signal

info that one individual produces that modifies behavior of other individuals

Signaler + audience have a common…

reproductive interest in communication occurring

Advertisement

variation in phenotype is correlated w/ a valuable trait

Would deceptive individuals out-reproduce honest advertisers?

No, preference would stop conferringj an advantage

One of two things muse be true

Signals aren’t actually advertisements

or

Signals are advertisements, but something enforces honesty

Handicapping Theory

Honestly can be maintained, if signal is costly in terms of the quality it’s advertising

Runaway Sexual Selection

describes how certain traits can become more common over time due to female preference

Why does female preference evolves?

They have more attractive sons than females w/out preference