Sexual selection Flashcards
what are the advantages to sexual reproduction?
- genetic variety, creates the potential for change in a population
- removal of deleterious mutations
What are the disadvantages of sexual reproduction
- energy in finding a mate
- loss of genetic ‘perfection’
- longer to reproduce
- disease risk
what are the advantages to asexual repro?
- dont need to find a mate
- maintain genetic perfection
- speed
- can make more offspring
what are the disadvantages of asexual repro?
- no creation of variation
- accumulation of deleterious mutations (mullers rachet)
- slow rate of evolution
- selective sweeps can eradicate all variation from a pop
what are coadapted gene complexes?
- genes that are well adapted to the environment
asexual populations have a clonal disadvantage when it comes to beneficial alleles because…..
it takes much more time to create beneficial alleles in asexual pops than sexual pops
due to linked genes, deleterious mutations can become ….. in asexual pops
fixated
WHAT is the biggest benefit of sexual repro?
- recombination provides mechanism for genomic repair, eliminated deleterious mutations
- parents can produce offspring with HIGHER fitness genotypes than themselves
What is sexual selection?
- form of selection that accounts for many elaborate traits an behaviors in species
- arises from difference in the ability to find and mater with members of the opposite sex
- (only occurs when there is competition for mates or offspring )
Why does sexual selection occur?
- sexual selection can cause evolution of traits that decrease the survival if a reproductive advantage compensates for the cost
what are the two forms of sexual selection
intrasexual selection: direct competition for mates between members of the same sex (usually male-male)
intersexual selection: differences in attractiveness for the opposite sex, non-random mate choice by females
How is sexual selection directed related to the relative investment in offspring production?
- the sex that invests more in reproduction (females) have fewer reproductive opportunities, and as a result they should be choosier of their mates, and become a limiting resource for males
limitations on reproductive successes differ for the sexes….
- females limited by fecundity and resources
- males limited by number of mates they can obtain
what is bateman’s princciple?
- greater variance in reproductive success among males than females
- because male gametes are not as limiting, male repro success linearly increases with number of mates
asymmetric nature of sexual reproduction (males having greater variance) can lead to
dramatic sexual dimorphism
exaggerated secondary sex traits are favoured because they increase male mating success…. however these exaggerated traits can
decrease survival
what are polymorphic male mating strategies?
- alternative mating strategies to avoid direct competition
- can be to ‘sneak’ in to mate with females, or ways to distract male competitors
what are direct benefits of female choice?
- female may benefit from increased nutrition, provisioning, or paternal care that increases fitness of offspring or reproductive output
what is the ‘good genes model’ ?
- elaborated male traits may be indicators of heritable genetic quality
- females that mate with these males will have offspring with higher fitness
What is the handicap principle?
- some males may have heritable trait that reduces viability
- only males with ‘good genes’ can survive despite the handicap
- the bigger the handicap, the higher the genetic quality of the male carrying the trait
what is the fisherian runaway/sexy son hypothesis?
- assortative mating within a population between males w exaggerated traits and females with strong preferences can lead to a genetic connection
- even if the exaggerated male trait decreases male fitness
- only benefit to female choice is that sons inherit attractive trait
in stable environments, ________ may be favored. In variable environments, ________ may be favored
ASEXUALLITY, SEX
what is the demographic two-fold cost of sex?
sexual females produce half as many offspring as asexual females because they must invest resources in both sons and daughters, while asexual females only produce daughters.
what is the genetic two-fold cost of sex?
asexual lineages will produce perfect offspring, while sexual lineages will produced mixed individuals that may not be as adapted the the environment
