Final exam Flashcards
(101 cards)
natural selection
heritable differences in survival and reproduction in a population
sexual selection
a subset of natural selection that acts on heritable traits affecting reproduction, ability to attract mate
Primary sexual characteristics
genitalia and reproductive organs differentiating males and females, affected by sexual selection
secondary sexual characteristics
differences between males and females that are not directly involved in reproduction, often decorative to attract mates
In which two ways does sexual selection operate in
intrasexual selection and intersexual selection
intrasexual selection
members of same sex compete each other for access to other sex, “male male” competition, favors evolution of weapons
eg: horns on dung beatles
intersexual selection
one sex selects other for reproduction, ‘female mate choice’, favors evolution of ornaments
eg: peacock tail
why are there two sexes?
gametes determine sex
male gametes: small motile gametes, cheep
female gametes: larger, immotile gametes, more expensive
anisogamy
animals with males and females, difference size gametes
isogamy
animals all produce same size gametes
Why are females normally choosy?`
Bateman hypothesis: male reproductive success is limited by number of eggs, male reproductive success is limited by number of mates, so females are choosier bc there is more competition for female gametes
parental investment theory
the sex that pays the highest cost should be choosier, this is usually females (incubation, feeding etc)
sex role reversal
when females compete for males that invest heavily in parental care and males are choosy
what happens during sex role reversal
females develop ornaments and weapons
eg: pipefish and seahorses (get preggo)
how can you tell who is choosier
animals with ornaments and weapons are often not the ones choosing
How do preferences evolve
1) sensory bias hypothesis
2) direct benefits of mate choice
3) indirect genetic benefits of mate choice
sensory bias hypothesis
Female mating preferences are a product of preexisting biases in females’ sensory system
thus biases evolved in none-mating contexts, males evolved to match pre-existing biases, like food!
eg: trinidadian guppies and the color orange!
direct benefit of mate choice
females can benefit by choosing males that provide direct benefits like food gifts, access to territories with food or enhanced parental care
Nuptial gifts: given to female before mating, provides nutrition
eg: fireflies transfer spermatophore during mating which has lots of protein
Indirect genetic benefits of mate choice
genetic benefits females obtain for their offspring by mating with males with high genetic quality
2 types: fisherman runaway selection and handicap principle/good genes
fisherman runaway selection
male trait coevolves with female preference and becomes increasingly exaggerated
1) female mates with mate with preferred trait
2) sons inherit trait, daughters inherit preference
3) strength of trait and preference increase (runaway) until costs outweigh the benefits.
assumes a linkage between gene for trait and preference
found for 23/43 species
handicap principle/ good genes
handicap principle: secondary sexual traits are costly, so only highest quality can display the most extreme forms
‘good genes’’: females benefit from choosing high quality males because offspring will inherit high quality alleles.
european tree frog: males call to attract females, offspring growth correlated with the attractiveness of males (most calls)
precopulatory sexual selection
sexual selection before mating
post-copulatory sexual selection
selection that occurs after mating, effects fertilization success
intrasexual postcopulatory selection
sperm competition between different males to fertilize eggs