Adaptations & Traits 3 Flashcards
sexual cooperation (2)
- when males and females share a reproductive interest in combining gametes
- females need access to sperm; males need access to eggs
sexual conflict (2)
- describes the divergent interests males and females have for sex
- both sexes have adaptations that take control over reproduction
sexual conflict: what are males selected for (3)
- to mate with female regardless of whether she’s fully ready
- to fight off other males or their sperm
- to induce females to invest in their offspring
sexual conflict: what are females selected for (3)
- mate only when they have the resources to support eggs/babies, and only as often as she needs
- mate with multiple males to have more diverse babies or to have sperm to select from
- hold back some investment for a future brood
sexual antagonistic coevolution (2)
- describes the arms race between sexes for adaptations to have better control over reproduction
- balance of cooperation and conflict
sexual selection: mate selection -> mating
- when the female “chooses” whether she wants to participate in mating with a male
sexual selection: mate selection -> mating
- when the female “chooses” whether she wants to participate in mating with a male
sexual selection: mating -> zygote (2)
- whether the female allows the male sperm to fertilize her egg
- whether the male sperm is able to outcompete sperm from other males
sexual selection: zygote -> adult offspring
- whether the mother invests a lot of resource into the males offspring or not
cryptic female choice (2)
- sexual selection that occurs after mating and is not easily visible because it occurs within her body
- describes how the females decision is not complete just because she allows the male to copulate
how can a female choose to reject a male after copulation has occurred? (5)
- dump the sperm
- don’t transfer the sperm to the right pace in the body
- re-mate so the second male’s sperm competes
- doesn’t ovulate
- doesn’t mature the eggs
isogamy (2)
- same-size gametes
- 2 mating types, called plus and minus
anisogamy (2)
- some gametes are really big (eggs), some are really small (sperm)
- animal and land plants and anisogamous
what does the difference in gamete size mean? (2)
- eggs are costly, sperm are cheap
- females have a larger consequence for choosing the “wrong” male as this could lead to relatively long term and large investment in unfit offspring compared to males
male-biased operational sex ratio (2)
- describes a mating pool where there are more males than females
- leads to more males competing for fewer females
why are operational sex ratios male-biased (2)
- females are tied up growing eggs, tending babies, etc; they aren’t in the pool of available mates all the time
- males are always looking for another mating; they are in the pool of available mates all the time
why do females tend to be more choosy than males (2)
- females don’t compete as much: they can afford to reject males because there are plenty more males in the mating pool
- females suffer a higher cost of a mistake: her investment per mating is likely higher than his
variance in reproductive success: males (2)
- have a relatively greater variance
- some males mate a lot, whereas others don’t at all due to competition
variance in reproductive success: females (2)
- have a relatively smaller variance
- females are more or less assured of some offspring, as long as they are healthy, because there is little competition
intrasexual selection
- males compete amongst each other and females mate with the winner
intersexual selection
- females choose among males according to their qualities
types of intersexual selective forces (4)
- direct benefits
- good genes, honest signals
- sensory bias
- runaway
direct benefits hypothesis (2)
- females are selected to choose males that give them resources or protection
- these direct benefits ensure the females can survive and reproduce and means that her genes have a better chance of getting into the next generation
direct benefits hypothesis: prediction
- males that offer more resources/protection are given a better chance to mate
good genes hypothesis (3)
- females are selected to choose males with good genes, because her offspring will then do better with these genes
- her genes will be in a good collaboration, building offspring bodies that survive and reproduce well
- not a direct benefit to her, but to her offspring instead
good genes hypothesis: prediction
- females should prefer traits if the presence of those traits in the males is correlated with/predicts him having good alleles for survival/reproduction, even if they don’t have direct benefits to her
honest indicator (2)
- an indicator trait that is costly to the male, and thus harms the male/lowers his survival rate
- females are selected to choose this harmful indicator trait because its stupid; its costliness guarantees that only high quality males can afford to make it
dishonest indicator
- a trait that any male can make; a trait that won’t predict male quality and is not useful for females to choose
why is a peacock tail an honest indicator
- its elaborateness is a sign of how much the male can afford to waste
sensory bias (2)
- female bodies and nervous systems are strongly selected for them to find food, avoid predators, and live life
- males have to “please” these bodies and those nervous systems
sensory bias hypothesis (2)
- first, ecological selection: different populations evolved different preferences
- then sexual selection: later, males take advantage of this attraction that females already have to the trait from ecological selection by evolving more exaggerated version of this trait
sensory bias hypothesis: guppies (2)
- first, ecological selection: different populations evolved different preferences for orange in food (algae, fruit, etc)
- then sexual selection: later, males take advantage of this attraction that females already had to orange (for feeding) by evolving bigger orange spots to attract females in another context (mating)
how is sensory bias different from the good genes hypothesis (3)
- males evolve bright, shiny “bling” to take advantage of biases in female sensory systems that evolved previously for other reasons
- the “bling” mimics signals that really do matter to the female (fruit, fire, etc)
- attraction may be a simple sensory attraction, and may not help the female choose a good quality mate
runaway sexual selection (2)
- once a population has alleles for a male trait and a female preference, a positive feedback loops can drive these alleles to fixations, regardless of how useful/indicative they are
- occurs because a linkage disequilibrium develops where the male trait allele and female preference allele occur together more often than expected by chance
what type is selection is runaway selection (2)
- frequency-dependent selection: the strength of selection on an allele depends on the frequency of the allele
- as frequency of choosiness rises, the selection for the male trait rises, which means that the selection for choosiness increases
what occurs as runaway selection proceeds, generation by generation (3)
- linkage disequilibrium gets stronger
- average preference of females increases
- male trait increases in frequency
runaway sexual selection: prediction (2)
- in a population with variable male traits and female preferences, there should be signs of linkage disequilibrium
- families should tend to have female preferences that match their male traits
what stops the runaway process of escalating the male trait and the female preference? (2)
- there may be no more genetic variability
- it may be too costly to produce the trait, so natural selection for survival stops the runaway
steps in runaway sexual selection (3)
- variability in male trait & female preference for it; non-choosy females are agnostic
- agnostic females mate indiscriminately; choosy females mate more with males with the trait, rising its frequency and generating a linkage disequilibrium between the alleles
- with each subsequent generation, the linkage disequilibrium gets stronger, the average preference of females increases, and the male trait increases in frequency
are the mechanisms for sexual selection by female choice mutually exclusive?
- no, more than one mechanism can be acting at the same time
when do the benefits occurs: direct benefits
- in her generation and to her directly, or to the resources she gives to her offspring
when do the benefits occurs: good genes
- in the next generation: to her offspring via the genes they will inherit from the male
when do the benefits occurs: sensory bias
- there may be no benefit at all
when do the benefits occurs: runaway
- there may be no survival/fecundity benefit at all, although the genes are selecting themselves, because of linkage disequilibrium
