prelim 2 (adaptation/speciation 1 - pop genetics 4) Flashcards
sexual selection
type of selection resulting from differences among individuals in their ability to mate or
fertilize eggs
- gives rise to diversity in morphology + behavior
individuals possessing traits that help them reproduce will be favored by sex selection
two fold cost of sex
asexual organisms can multiply faster than sexual organisms.
costs of sex
- finding an appropriate mate
- parents are less related to their offspring (r = 1 in asex but here r = 0.5)
- risk of contracting STDs
why is sex common
- gene recombination for genetic exchange; allows for the weeding out of deleterious mutations
- combining favorable mutations more quickly
- allows for faster adaptation again thru
reshuffling of genetic diversity
cost of asexual reproduction
- entire genome passed down generations
- deleterious mutations accumulate
- accumulation results in genetic load
sexual dimorphism
phenotypic difference between the male/female in population
- size, color, behavior, physiology
sex selection trade offs
investment strategies differ between species and the sexes
anisogamy
gametes are different sizes
- egg tends to be larger; female might need to have diff life history strategy to account for energy
- fruit fly exception w the v long sperm
internal fertilization
in females usually; evolved multiple times
- sets up different level of investment
- females have large energetic investment; specialized adaptations for offspring care in females
- internal fertilization means those carrying are certain of their offspring
operational sex ratio
ratio of males to females available for reproducing at given time
- how strong sexual selection is
male biased OSR and stronger sexual selection on males (bc females get pregnant) - when there is larger male population and females are not reproductive due to pregnancy and other
variance in reproductive succes
higher male variance in a more male-biased OSR
- stronger sex selection in males
- lower variance in female reproductive success
male-biased OSR
males are most likely to maximize fitness by fertilizing eggs
females invest in choosing good mates, producing good eggs, provisioning offspring
females-biased OSR
females control territories: invest in attracting mates bc there are more female than male
males: invest in high quality mates and offspring care
strength of sexual selection
higher in mating system where variance in reproductive success is higher
-* stronger in species that mate w multiple during fertile period
- members under stronger selection = mating competition; weaker selection = mate choice
cryptic females choice
females can store sperm and decide later which to use more of
geographical barriers= extrinsic
mountains, rivers, oceans, physical separation
- allopatric and peripatric
intrinsic = reproductive barriers
difference in attraction and stuff
or infertile children
- parapatric and sympatric speciation
allopatric speciation
ancestral pop divided by extrinsic barrier
peripatric
small number of individuals cross a barrier and are separated geographically
- founder affect?
vicariance
formation of geographic barriers that separate a population
dispersal and colonization
populations become separate by dispersal to new areas
parapatric speciation
occurs when species is spread out over large geographic area that causes differences; mate with ones closer to them until they diverge more and more
sympatric speciation
some individuals begin to exploit a new niche and mate with other occupying the same niche
behavioral isolation
utilize different mate recognition system