envs lecture 12 Flashcards
what is found at all levels of all biological organization
cooperation and conflict
examples of cooperation
seemingly altruistic behavior to gather food, raise offspring, defend resources like food/nest
example of conflict
infanticide, siblicide
what’s a useful way to think about social interactions among individuals
start w/ a table of the effects on actor and recipient
how are the effects on the actor and recipient classified
w/ respect to how they effect the fitnesses of the two individuals (increase in fitness or decrease in fitness)
what does mutualistic behavior do (in terms of fitness)
increases fitness for both actor and recipient
what is mutualistic behavior a form of
cooperation
what is altruistic behavior
negative/costly effect on actor but benefits the recipient by increasing fitness
what is altruistic behavior a form of
cooperation
what is selfish behavior
benefits actor by increasing fitness, but negative effect on recipient by decreasing fitness
what is selfish behavior a form of
conflict
what is spiteful behavior
both a negative effect on actor and recipient; fitness decreases for both of them
what is spiteful behavior a form of
conflict
what is cheating
individuals cheat when they can benefit from actions of others without providing reciprocal benefits in return
describe cheating vs. cooperation
if cheating has high fitness in population of cooperators, then mutation that causes cheating will spread and cooperation will collapse
so what is big question/puzzle
how does natural selection favor cooperative behavior when cheating is a possibility
give example of cheating in unicellular slime mold
when food is scarce, individual cells aggregate intoo a slug that can move around, slug –> mushroom like structure cells form spores that disperse while those in stalk die w/o reproducing
basically what happens to cells in stalk in unicellular slime mold
sacrifice themselves for benefit of cells that make spore
what gene allows slime mold cells to cheat
chtA mutation
what does chtA mutation cause
them to behave selfishly and avoid contributing to the stalk
what happens in a mix of wild-type cells and chtA cells
mutant cells become concentrated in cap and are more likely to form reproductive spores
what happened to frequency of selfish mutant allele over 11 cycles
frequency increase
what happens to cheating mutation, and what is question
cheating mutation doesn’t go to fixation, why don’t we see end of cooperative behavior and fixation of cheating mutation in population?
what did biologists think until 1960s
evolution favored traits for group selection (that benefited population or species)
but what do we know about group selection
group selection is uncommon
why is group selection uncommon
b/c of strong fitness advantage of cheating
so why hasn’t cheating mutation spread to fixation?
colonies that have high relatedness evolve resistance to cheaters
describe competition experiment w/ slime mold
compared evolved cheaters (non-fruiters) and both their ancestors and evolved fruiters (wild-type) which are both cooperative.
evolved fruiters are fruiters that have evolved in presence of cheaters
if nonfruiters cheat the ancestor as expected, resistance to cheating will be established. if they cheat the evolved fruiters less or not at all, shows that resistance to cheating has evolved in experiment.
if nonfruiters cheat ancestor and evolved fruiters equally, we would expect to see same number of nonfruiters in study for both mixtures
describe results of competition experiment
evolved fruiter evolves resistance to cheating before cheating sweeps thru population and multicellularity is lost
colonies are able to evolve resistance against cheating.
when colonies closely related, stronger resistance
what conditions can cooperation or altruism evolve
mutualism, reciprocity (form of mutualism), kin selection
what is mutualism
cooperation among unrelated individuals where both actor and recipient benefit
what is reciprocity
another form of mutualism; individuals reciprocally increase each other’s fitness
what is kin selection
altruism among related individuals
give example of cooperation among non-kin (unrelated individuals)
flocking behavior
what does flocking behavior do
lowers risk of predation among individuals in a group –> less likely predator will focus on individual
what is flocking behavior
selfish herd effect
what does selfish herd effect do
lowers risk of predation among individuals in groups
what is shared vigilance
groups lookout for predators together; more time can be devoted to grazing in larger herd
give another example of cooperation among non-kin
starlings flock in response to predator –> selfish herd effect
what is the point of selfish herd effect
safety in numbers
another example of cooperation among non-kin
wolves & cooperative predators (lions, hyenas) hunt cooperatively in packs to take down prey a single individual couldn’t take down
what does hunting large prey require
cooperative behavior
what do some systems have
delayed benefits
what are delayed benefits
helping at the nest where more than a pair takes care of young at a nest; sometimes helpers are kin, sometimes they aren’t
what do manakin leks do
cooperation among non-kin; delayed benefits
describe delayed benefits in manakin leks
two males court female. female goes w/ dominant males. when dominant male dies, subordinate male takes over
what do baboons do
reciprocity
what did robert trivers suggest
reciprocity; cooperation can involve when one individual provides fitness benefit to another, as long as 2nd individual returns favor
what is reciprocity
individuals provide reciprocal favors to one another that both provide fitness benefits
when can cooperation evolve
when individuals provide reciprocal favors to one another that both provide fitness benefits
what can favor cooperative behavior
repeated interaction
what does cooperation/reciprocity require
requires repeated interactions and ability to recognize individuals
describe reciprocity in yellow baboons
offspring of female yellow baboons that have strong bond w/ females other than mom have better survival
when can cooperation be enhanced
when selfish individuals are punished
where is reciprocity common
mammals, including humans
what can mathematical models predict
conditions under which reciprocity is favored by natural selection
what are evolutionary stable strategies (ESS)
mathematical models can predict conditions under which reciprocity is favored by nat selection
what did john maynard smith do
evo biologist; introduced game theory from econ to study evolution of social behavior
what is famous scenario
prisoner’s dilemma
prisoner’s dilemma
two individuals do better by acting selfishly, but if they both act selfishly they do worse than if they cooperate
what does game theory show about selfishness
selfish behavior is favored if individuals interact only once, but repeated interactions can favor cooperation
when is selfish behavior favored
if individuals interact only once
when is cooperation favored
repeated interactions
describe prisoner’s dilemma
2 thieve commit crime, caught and isolated.
if they both defect & incriminate the other, each get 2 years in prison.
if both remain silent/cooperate, each get one year
if one defects and other doesn’t, one goes free other gets 3 years.
what is best strategy in prisoner’s dilemma
only one defects
what is worst strategy in prisoner’s dilemma
both defect
what happens if these individuals interact repeatedly
strategy changes; gang members don’t rat each other out
what is one kind of behavior w/ high fitness in interactions w/ other individuals
tit for tat
describe this ‘tit for tat’ behavior
cooperate on first interaction, do whatever the other did on the previous round
what is this ‘tit for tat’ behavior an example of
situation where individuals interact repeatedly
what is cooperation
activity/behavior that provides a benefit to other individuals and to the actor
what is altruism
involves behavior that enhances fitness of other individuals, but LOWERS fitness of the actor
how can we explain altruism (in terms of what)
kin selection
what is kin selection
helping out close relatives to increase their fitness
when does kin selection favor altruism
only if individuals more likely to help kin than non-kin
how do species recognize kin
cues, like distinctive calls or odors
what is Hamilton’s rule
rB > C
what is r
relatedness
what is B
fitness benefit to recipient
what is C
fitness cost to actor
what does Hamilton’s rule say
relatedness times fitness benefit to the recipient MUST be greater than the fitness cost to the actor
when is Hamilton’s rule met
when altruistic behavior can evolve
what did JBS Haldane say
when asked if he would give his life to save a drowning brother, he said “no, but I would to save two brothers or eight cousins”
why did JBS Haldane say that
relatedness; we share 50% genes w/ siblings and 25% w/ cousins
what is better than us reproducing ourselves
saving two siblings or 8 cousins, cuz our offspring are only related to us by 50%
what was Haldane referring to
inclusive fitness
how much of genes do parents and offspring share
50%
how much of genes do cousins share
25%
who came up w/ idea of inclusive fitness
JBS Haldane
what is inclusive fitness
the relative number of an individual’s alleles that are passed onto future generations, both directly AND indirectly
how are individual’s alleles passed on to future generations directly
as a result of an individual’s own reproductive success
how are an individual’s alleles passed on to future gens indirectly
when the individual helps relatives who also carry a proportion of their alleles
what is this component due to indirect called
kin selection
what was the idea behind inclusive fitness
relative # of someone’s alleles passed down are a combo of direct fitness and indirect fitness
what does W.D. Hamilton’s rule say
selection favors genes for altruism if rB-C>0; ( relatedness of actor to the beneficiary * benefit in fraction of additional offspring resulting from helping - minus cost (in loss of offspring) to the actor from helping is greater than 0)
what is W.D. Hamilton’s rule
rB-C > 0
what does W.D. Hamilton’s rule say
altruism favored by natural selection IF
relatedness of actor to beneficiary x benefit to recipient (in fraction of additional offspring resulting from helping) - cost to altruist (cost in loss of offspring) is greater than 0
what can we simplify this equation to
r > C/B
what does r > C/B mean
genes for altruism more likely to spread when there’s genetic basis for behavior, benefits to recipient are great, cost to actor is low, and participants closely related
when are genes for altruism more likely to spread
genetic basis for behavior, benefits to recipient are great, cost to actor is low, participants closely related
talk about test of hamilton’s rule in pied-kingfishers
communal breeders that tunnel into mud banks. sex ratio biased towards males. have helpers at the nest; 2 types, primary and secondary helpers
primary helpers forgo mating for the first year, stay at natal nest to help raise siblings.
secondary helpers help unrelated pairs
delayers do nothing and wait until next year
60% of primary helpers breed the following year
91% of secondary helpers breed the following year
33% of delayers breed the following year
males do more helping
related individuals do more helping
secondary helpers do better than all the others the following year
what are primary helpers
forego mating for first year and stay at natal nest to help raise siblings
what are secondary helpers
help unrelated pairs
what are delayers
do nothing and wait until next year
what are results of kingfisher test
inclusive fitness is highest for a primary helper, high secondary helper, low for a delayer
does it pay for secondary helper to assist non-relatives
yup
another example of altruism in wild turkeys
wild turkeys display in pairs of dominant and subordinate brothers. dominant male has higher fitness.
presence of subordinate increases reproductive success of dominant male.
subordinate doesn’t mate, so cost of helping brother is cost of not displaying solo
what was finding in turkey experiment
there is an inclusive fitness advantage to going solo; or advantage to this altruistic behavior of subordinate male
what is most extreme cause of altruism
eusociality
what is eusociality
colonies of individuals where most colony members do not reproduce and a few do
what animals are in eusociality
naked mole rats, termites, ants, wasps
what is eusociality
living in a cooperative group where one female and several males are reproductively active, nonbreeding individuals care for young, protect, provide for group
what’s up w/ naked mole rats
only known eusocial mammals
what are naked mole rats
diploid
why are naked mole rats in a eusocial structure
cuz of harsh environment they live in
what are famous examples of eusociality in insects
ants, bees, wasps, termites
describe eusociality in termites
queen termite is attended by small, sterile workers and large-headed sterile soldiers
what do ants do
engorged w/ nectar, hang from roof of nest’s ladder. they regurgitate nectar to worker nestmates
what do wasps do
colonial nests
what is involved in evolution of eusocial insects
kin selection likely involved
what explains cooperation and conflict and why some individuals forgo reproduction and help their relatives in the haplodiploid system of relatedness
kin selection
what does kin selection explain
in haplodiploid system of relatedness, kin selection explains cooperation and conflict and why some individuals forgo reproduction and help their relatives
how are organisms related in diploids
offspring and parents are 50% related, siblings are 50% related
what happens in haplodiploid systems
fertilized eggs are diploid, develop into females. unfertilized eggs are haploid, develop into males
what happen to fertilized eggs in haplodiploid system
develop into females
what happens to unfertilized eggs in haplodiploid system
develop into males
so is the coefficient of relatedness the same in diploid system as it is in haplodiploid system
nope
describe coefficient of relatedness in haplodiploid system
females are more closely related to sisters, r = 75%, than she is to offspring, 50%, and less closely related to brothers, r = 25%
who are females most closely related to in haplodiploid system
her sisters, then offspring, then brothers
what do social interactions often involve
conflict
what must males and females do in order to produce offspring
cooperate
but what else is pervasive between mates
conflict
what is present between mates
conflict and cooperation
what happens as effort by one parent increases
the other’s decreases
what happens if you plot effort of male and female
intersection shows ESS; will evolve to ESS no mater what initial conditions are
can conditions occur where optimal curves for sexes don’t intersect
yup; ESS is care only by female (scorpion) or male (poison dart frog)
what else can conflict include
siblicide and infanticide
who does siblicide
brown booby, owls, hawks, herons, pelicans
when does siblicide happen
when food is limited
does siblicide happen when food is plentiful
no, young don’t compete and parents raise a full nest
who does infanticide
hyenas and lions
when does infanticide occur
social cooperative mammals; males take over a harem/group of females, kill young so females can go into heat and reproduce
what does infanticide do
eliminates alleles of competitors, allows females to become fertile and sexually receptive
where does infanticide occur
social groups w/ more females than males
can some species kill their own offspring
yup
when do some species kill their own offspring
social situations where offspring survival would decrease even more if all offspring were allowed to compete w/ each other
what is one last major form of conflict
cannibalism
who does cannibalism
tiger salamanders
when do tiger salamanders do cannibalism
when at high population density
what kind of balance occurs in many biological systems
balance b/w conflict and cooperation
what can males and females and parents and offspring have
aligned or conflicting interests
what do ESS do
can predict which phenotype or balance of phenotypes is optimal
what does altruism do
benefits other individuals, reduces individual fitness of the actor
what does cooperative behavior do
increase individual fitness of both donor and recipient
what does inclusive fitness explain
evolution of altruism
what does individual selection explain
situations; behaviors
what does kin selection explain
evolution of altruistic behaviors
