lecture 18 Flashcards
what is sexual reproduction?
it involves 2 parents
mitosis and meiosis form gametes (egg, sperm) which carry half chromos of parents and fuse together during fertilization
what is asexual reproduction?
1 parent is involved and three is no meiosis in chrome number
offsprings get 100% parent chromos and are genetic repliacas (no crossover, no recombination, no segregation)
what is the cost of sex?
it takes time + energy to attract mate
they expose themseves to predation
increase energetic cost of hunting mates and moving to breeding grounds
there’s a risk for sexually transmitted diseases
cost of producing males, males are a bad evolution investment
there’s 50% less genetic transmission
can break up adaptive gene combos, offsprings might becomes less adapted
what is the paradox of sex?
tries to find benefits of sexual reproduction which overcomes its costs
what is the two-fold cost of meiosis?
sexual females can only contribute 50% of genes while asexual females can contribute 100%
what is transmission bias?
where asexuality will be favoured as in an equal number offsprings, asexual females can pass down 2x as many genes
how can asexual reproduction positively affect offspring fitness?
it can maintain favourable allele combos as genes will be perfectly transmitted
how can sexual reproduction negatively affect offspring fitness?
it can continually recreate unfavourable allele combos/break up favourable combos
how can sexual reproduction positively impact offspring fitness?
it can bring together new favorable mutations and eliminate harmful mutation more efficiently like only passes on positive mutations
in what scenario is sexual reproduction favourable to asexual reproduction?
if enviros are very variable, then sexual reproduction can create more variable offspring which are more likely to match unpredictable enviro
what is tangled bank hypothesis?
the idea the enviro is spatially heterogenous/not uniform through spaces
what is the red queen hypothesis?
talks abt temporarily heterogenous enviros, theorizes that if enviro will change in the future producing the same thing repeatedly might not be a good idea
favours variation
how can asexual reproduction negative affect offspring fitness?
it can cause accumlation of negative, deleterious mutations through accumulation of premature stop codons
where can asexual organisms be found on a phylogeny tree and why?
asexual species are usually at tips of phylogenies, its rare for an entire phylogeny to be asexual, their evolutionary potential in long term may be low due to lack of genetic variation which mayb cause higher extinction rate
how to asexual and sexual reproduction differ in advantage type?
asexual reproduction has short term advantage while sexual reproduction has long term advantage
what is outbreeding?
mating w/ less closely related than random is outbreeding
what is inbreeding?
mating w/ more closely related than random (relatives)
what is selfing?
selfing involves 1 parent, there is meiotic division of gametes and fusion of gametes but you fertilize you own eggs aka mating w/ self, this happens in plants where pollen fertilizes ovules of same individual hermaphoritic organisms (most plants, many animals) self fertilize
what is outcrossing?
outcrossing involves 2 parents, meiotic division of games and fusion of gametes and involves mating w/ others
what is a local pop substructure?
local pop substructure mean individual found in same location tend to be related so there is high potential for mating w/ close relative
what are methods plants use to avoid inbreeding?
large showy flowers are used to attract pollinators
hermaphroditic sepcies have diff timing for male and female reproduce ex. in flowering plantts pollen is mature before stigma are receptive
go through a male phase then a female phase
what is self-incompatibility?
genetic/morphological mechanisms used to avoid selfing (fertilization onelft)
what are some examples of self-incompatibility?
dispersal which is often sex biased where all individuals of one sex will disperse while other will stay in native home
delayed maturation means offspring will not be sexually active at same time as parents
extra pair copulation where they will have a mate which is not their social partner
additionally there is evidence animals can recognize kin and will avoid them
what are the effects of inbreeding on genotype frequency?
inbreeding (non-random mating) changes genotype frequency (A1A1, A1A2, A2A2), increases homozygosity, decreases heterozygosity, but does not change allele frequency (number of A1 and A2 overall)
the more close mates are related, the quicker heterozygous declines
it decreased by 50% per gen through self-fertilization
what is inbreeding depression and what doe sit entail
inbreeding depression is reduced fitness in inbred offsprings compared to outcrossed offspring
its shown in reduction in viabilility (survival) and fertility
inbreeding depressing lowers fitness by exposing deleterious negative alleles
how do selfing plants evolve?
selfing flowers have reduced petal size and reproductive organs are in close contact w/ each other
how do selfing plants evolve?
selfing flowers have reduced petal size and reproductive organs are in close contact w/ each other
what’s the fitness of advantage of selfing?
selfing variant has 50% transmission advantage, this might be the major advantage which leads to the evolution of selfing
selfing flowers tend to have larger ranges than outcrossing flowers
