ch.11: sexual consequences and outcomes Flashcards
Cell Division
asexual reproduction without meiosis or fusion of haploid gametes through fertilization
EX: bacteria
Parthenogenesis
mode of reproduction in which female sex cells undergo meiosis but are NOT fertilized by sperm (all female and each produce ONLY daughters)
Hermaphrodites
reproduction that produces female and male gametes
EX: flatworms
Twofold cost of sex
asexual lineages multiply faster than sexual lineages
Mullers Ratchet
the process by which the genomes of an asexual population acculmate deleterious mutations in an irreversible manner
*asexual
*has genetic hitchhiking
Genetic Load
the burden imposed by the accumulation of deleterious mutations
Deleterious alleles become ____ in ____ populations but are purged from ____ populations.
fixed
asexual
sexual
Red Queen Effect
for coevolving population, to maintain relative fitness, each population must constantly adapt to the other
EX: New Zealand Snails
Anisogamy
sexual reproduction involving the fusion of two dissimilar gametes
Operational Sex Ratio (OSR)
ratio of males to females capable of reproducing at a given time and slower rate of reproduction by females leads to male biased OSR
Intrasexual
within a sex
female vs. female
male vs. male
Intersexual
between sex
female vs. male
Ornaments
attractive traits that increase mating success
Arnaments
weaponry used to outcompete other individuals
Direct choice
benefit the female directly
EX: food, nest sites, protection
Indirect benefits
benefits that affect the genetic quality of the females offspring
Female preferences are often _____.
consistent (gets passed down to offspring)
Sex Role Reversal
females compete over access to
EX: wattled jacanas, sea horses, pipefish
Fisher’s Principle: Frequency-dependent selection
fitness is dependent on the frequency of a phenotype or genotype in a population
Trivers-Willard Hypothesis (1973)
proposed that natural selection could drive OSR away from 1:1 under certain conditions
Males benefit when mother invests ____ in current offspring.
more
Females benefit by _____ for future offpsring.
saving resources
Senescence
the deterioration in the biological functions of an organism as it ages
Senescence results from a ____ of reproduction early in life verses body maintenance for longevity
trade off
Disadvantages of Sex
- Twofold Cost of Sex
- Search Cost
- Reduced Relatedness
- Risk of Sexually Transmitted Infections
Twofold Cost of Sex (dis)
asexual lineages grow more rapidly in each generation because all progeny can produce offspring
Search Cost (dis)
Males and females must locate each other in order to mate
*involves time, energy and risk of predation
Reduced relatedness (dis)
sexually reproducing organisms pass only half of their alleles to their offspring
Risk of Sexually Transmitted Infections (dis)
mating between males and females provides an effective means of transmission for many pathogens
Advantages of Sex
- Combining Beneficial Mutations
- Generation of Novel Genotypes
- Faster Evolution
- Clearance of Deleterious Mutations
Combining Beneficial Mutations (adv)
sexual reproduction can bring separate beneficial mutations together in a single individual faster
Generation of Novel Genotypes (adv)
through recombination, meiosis provides an opportunity for paired chromosomes to cross over which creates a unique combo of alleles
Faster Evolution (adv)
offspring of sexual parents will be more genetically variable than offspring of asexual reproducing parents
*can increase speed of evolutionary response to selection and is critical for maintaining resistance to parasites (red queen effect)
Clearance of Deleterious Mutations (adv)
sexual populations can purge themselves of harmful mutation with genetic recombo & asexual populations steadily and irreversibly accumulate mutations until a lineage driven extinct (Muller’s ratchet)
What makes sex beneficial?
red queen effect
How does anisogamy result?
differential investment in reproduction
Females have ____ paternity.
Males have _____ paternity.
certain
uncertain
What alters OSR?
asymmetrical parental care
Why might female preferences arise?
may arise from preexisting sensory bias
Monogamy
one male pairs with one female
Sexual Monogamy
exclusive
Social Monogamy
may cheat
Polygyny
males mate with multiple females
Polyandry
females mate with multiple males
Polyandry ____ for male traits that ____ paternity rates.
selects, increase
Sperm Competition
a form of sexual selection that arises after mating when males compete for fertilization of a females egg
What does sperm competition do for evolution?
drives evolution of larger testes
Sexual Conflict
traits that confer a fitness benefit on one sex but cost to the other
**traits coevolve antagonistically
Sexual conflict leads to ____ between males and females.
antagonistic coevolution
How does anisogamy influence sexual selection?
females invest more into reproduction than males because female gametes are more costly to produce more than male gametes
-males usually maximize fitness by mating with more females
-female fitness is limited by fecundity = don’t increase their fitness by mating with multiple males
-females attract more mates is not necessarily favored
How does OSR influence sexual selection?
-if ratio skewed it can intensify sexual selection
-more male biased then males will experience intense competition for access to mates
How does the opportunity for selection influence sexual selection?
-arises from variance in fitness in a population
-stronger on males when there is more variance in male fitness
Good Genes Hypothesis
the traits females choose when selecting a mate are honest indicators of the males ability to pass on genes that will increase the survival or reproductive of female offspring
Sensory Bias Hypothesis
sexual selection of females mating preferences are by products of natural selection
