midterm 2 Flashcards
what is reproductive success a function of
probability of survival and the number of offspring
what is lifetime reproductive success a function of
survival and reproduction
how strong is the selection on late acting deleterious mutant alleles
weak
why is the average sometimes less than the optimum
lifetime reproductive success
optimum allocation
what is fitness
the lifetime number of offspring that survive to reproduce
what does selection lead to if there is multiple bouts of reproduction
leads to individuals investing less than optimum amount of resources in each bout
what two trade offs together make optimal clutch size
the more offspring the smaller they are
the bigger the offspring the more likely they are to survive
in general, what is the selection for in regards for parents investing in either sex of their child
invest equally between sexes
what sex has more babies on average and what kind of selection is this
rarer sex
negative frequency selection
when does the generality that sexes are selected for equally fail
when differential investment has different payoffs between sexes
in red deers what sex do highly dominant females tend to have
males
why are there usually fewer males born on average in sexually selected mammals
males are bigger so more likely to die in utero
what is the Trivers-Willard hypothesis
suggest that parents who are in good condition will bias investment towards sons
why are sons more likely in good conditions, and daughters in poor conditions
hight quality males expected to reproduce more than high quality females
poor quality females expected to reproduce more than poor quality males
how does an individual achieve higher fitness
greater reproductive fitness (more offspring)
greater mating success (more mates)
more viable offspring
greater survival (live longer)
what is heterogamy
when males have smaller, cheaper, more motile gametes
females have bigger, more expensive, less motile gametes
what is a hermaphrodite
individuals capable of producing both eggs and sperm
what is isogamy
when gametes are all same size
no males and females
what are primary sexual characteristics
characteristics that are unique to one sex and essential for reproduction
what are secondary sex characteristics
characteristics that are unique to one sex that are not essential for reproduction
in sexual species what does selection act on
variation associated with investments in finding, attracting, and mating
for both males and females
what sex is more likely to have secondary sex characteristics
males
what are the two areas that sexes can differ in parental investment
gamete production
parental care
what sex has greater investment in gamete production
females
what is the investment in parental care involve
bearing and raising offspring
what limits females in regards to reproduction
resources
what limits males in regards to reproduction
access to females
what is Bateman’s principle
in most species variability in reproductive success in greater in males
according to bateman’s principle, what areas will males have greater variation
mate number
offspring number
correlation between mate number and offspring number
to the extent there is Vg, the scope of selection will be a function of what (bateman’s principle)
mate number
offspring number
correlation between mate number and offspring number
does the total number of mating differ between sexes
no
takes 2 to make offspring
why are sexes different
since selection acts on them differently on them
sexes evolve in different environments (different selection regimes) leading to different adaptations
what does competition between males for females lead to
sexual dimorphism
what is the level of dimorphism a good measure for
asymmetry between sexes in regards to investment in offspring
and variances in mating success
what is sexual dimorphism
the systematic difference in form between individuals of different sexes of the same species
how can asymmetries predict dimorphism
when sexes have similar amounts of care (both high/low) little dimorphism
when sexes have different amounts of care done by each sex (one low one high) one that does less will have dimorphism (often males)
what is sexually antagonistic selection
when males and females have different optima for their traits
one would benefit for selection of a trait that the other would suffer for
how are sexual selection and sexually antagonistic selection similar
both select for an individuals optimum trait
how do sexual selection and sexually antagonistic selection differ
sexual selection models argues for benefit of one sex, and ignores the fitness of opposite sex
sexually antagonist selection models argue that net cost to one benefits other
when does sexual antagonistic coevolution occur
when selection favours different outcomes in males vs females
what does sexually antagonistic coevolution lead to
arms race between sexes which gives rise to adaptation and counter evolution
how are sexual conflicts resolved
sex limited gene expression
selection favouring different values for a phenotypic traits between males and females
where are 97% of sexually antagonistic effects found
X chromosome
what is evidence for resolved sexual antagonistic selection and why
sexual dimorphism
since most of genome is shared
what happens as a result of the asymmetric limits to reproductive success
sexes will use different strategies to maximize reproductive success
what are the two models of sexual competition
intersexual selection
intrasexual selection
what is intersexual selection
females
male-female = female choice
females can afford to be choosey
what is intrasexual selection
male-male = competition
compete for females
what are the forms of intrasexual selection
predating competition (combat, contests, etc..)
postulating/prezygotic competition (spem competition)
post zygotic competition (infanticide)
when would prezygotic competition be good
if female has multiple mates, sperm may compete for access to egg, or males guard/sequester females or scoop out other male’s sperm, or block hole
why are females choosey
direct benefits: chooses a male who will maximize her reproductive fitness (#of offspring she’ll have)
Indirect benefits : female chooses male who will maximize her offsprings’ reproductive success (more grandkids)
What are the methods that indirect benefits can happen through
good genes hypothesis
sexy sons
what is the good genes hypothesis
the traits that a female chooses when selecting a male are honest indicators of the male’s ability to pass on genes that would improve the offsprings’ fitness
what is cryptic female choice
when in some species the female cannot choose who to mate with so the choice happens post-mating via sperm rejection/ejection
what is the sexy sons (runaway sexual selection) hypothesis
female preference drives selection for an exaggerated trait, that doesn’t increase survival, growth, or fecundity, but does increase ability to attract a female
what are the loose ends of good genes and the sexy sons hypotheses
sensory bias
sex role reversal
male choice
purging
what do the good genes and sexy sons hypotheses explain
why a female might choose a male based on a trait that provides no direct benefit
what is sensory bias and exploitation
females have extrinsic preferences for certain cues that have evolved through natural selection
males may try and take advantage of their affinity towards these traits
what cycle is sensory exploitation part of
sexually antagonistic selection
what is sex role reversal
in some species males are limited by resources, and females in access to males
what can high variance in male mating success lead to
small effective population sizes = drift
as well as genetic purging
what is a monomorphic species
when males and females of a species look the same
why can it be hard to draw a line between sexual and natural selection
they can overlap
what does sexual selection interact with
life history traits
why do we use theoretical modelling to decide if these hypotheses make sense
since these concepts are very hard ti observe in the real world
what is is called when both the actor and recipient benefit
mutual benefit
what is it called when the actor benefits at the expense of the recipient
selfishness
what is it called when the recipient benefits at the expense of the actor
altruism
what is it called when neither the actor or the recipient benefit
spite
what is group selection and does it actually work that way
the needs/interests of a group can select for an altruistic allele to increase in frequency
no
what is kin selection
type of natural selection that considers the roles relatives play when evaluating the genetic fitness of an individual
what is inclusive fitness
individual fitness + fitness of close relatives
how do you calculate coefficient of relatedness
- trace all paths from actor to recipient
- calculate probability of each link
- multiply the probabilities of a single path
- add path probabilities together
what behaviours must be met for kin selection to happen
- individuals in population vary in behaviour
- behaviour is heritable
- behaviour enhances fitness of relatives
what is Hamiltons rule
a costly behaviour will increase in a population if rB > C
what must happen for an altruistic trait to increase in frequency
increases an individual’s inclusive fitness
what is eusociality
overlapping adult generations in which non-reproductive individuals participate in the cooperative care of young
what two things are associated with eusociality
haplodiploidy - sisters are more closley related than offspring or anyone else (r=0.75)
ecology and life history- usually in groups in complex nests where adults provide extended care for the young
what is a green beard effect
when an altruistic allele also causes a visible trait allowing others with this trait to recognize them and behave altruistically towards them
what should happen for a green beard population to sustain itself , why
polychromatic green beards
needed to void cheating and fixation that would erode the selective benefit of the signal
How can the evolution of costly behaviours in small closely related groups usually be explained
kin selection
How can the evolution of costly behaviours in less closely related groups usually be explained
reciprocal altruism
in what populations is reciprocal altruism most common
long living social organisms with good memories
when is altruism favoured
when B is large and C is small
when should investment stop
when B < C
B/C < 1
why is there parent offspring conflict
mom reaches B/C = 1 before offspring
what causes the conflict between siblings
competition for parental resources
explain spite
anti green beard
if recipient definitely doesn’t have the altruistic allele, then cost to actor can be outweighed by benefit to others with altruistic allele
what is evolutionary game theory
alleles for generous tit-for-tat strategies
