Ch. 17 Homework

Order the payoffs in the prisoner's dilemma game from lowest to highest.

1.) payoff to an individual that cooperates against an opponent that defects 2.) payoff to an individual that defects against an opponent that defects 3.) payoff to an individual that cooperates against an opponent that cooperates 4.) payoff to an individual that defects against an opponent that cooperates

eusociality

A form of extreme sociality involving reproductive division of labor and the cooperative rearing of offspring.

Which of the following is true according to modern models of group selection?

Between-group selection can sometimes lead to the evolution of social behaviors that are not favored by the within-group selection

parent-offspring conflict

Conflict that arises because the genetic interests of offspring and their parents are not perfectly aligned.

Identify whether each statement correctly or incorrectly reflects the relationship in the graph between mating system and parent-offspring conflict. Assume that we are considering maternal investment in offspring.

Correct: For a species in which the mother provides most parental care, inclusive fitness theory predicts that offspring should be selected to extract a higher level of direct parental investment under a polyandrous mating system than under a monogamous mating system. Under polyandry, the future offspring of a female's current offspring will not necessarily be full siblings. Incorrect: We can use this graph to determine the optimum level of direct parental investment from the perspective of a focal offspring. When the mating system is polyandrous rather than monogamous, we expect an increase in the slope of the red line representing maternal cost relevant to the offspring.

This phylogeny supports the hypothesis that eusociality should evolve most readily in monandrous hymenopteran lineages, that is, in lineages in which the queen of a colony mates with only one male. Each independent origin of eusociality is indicated by a different color for that clade. Why does inclusive fitness theory generate this prediction?

In a monandrous hymenopteran species, all females in the colony will be full sisters, and the coefficient of relatedness between sisters is higher than the coefficient of relatedness between females and their own daughters. Therefore, caring for sisters beats out producing offspring in terms of inclusive fitness.

direct fitness

The expected number of viable offspring an individual produces. (an individual's own lifetime reproductive output)

indirect fitness

The incremental effect that an individual's behavior has on the fitness of its genetic relatives. the effect of an individual's actions on the lifetime reproductive output of a genetic relative

In mice, the Igf2 gene, which is involved in production of a growth hormone, is maternally imprinted. The Igf2r gene, which is associated with binding and reducing activity of the growth hormone, is paternally imprinted. Which of the following statements best explains why this observation makes sense under the tug-of-war model for the evolution of genomic imprinting?

The optimal level of investment in currently developing offspring is higher for males than for females, so the maternal chromosome expresses a growth-suppressing gene, and the paternal chromosome expresses a growth-promoting gene.

inclusive fitness

The sum of indirect and direct fitness, inclusive fitness serves as a measure of the total contribution that an individual makes toward producing copies of its genes in the next generation, whether in its own descendants or in those of its relatives.

costly signaling theory

The theory that individuals with conflicting interests can communicate honestly using signals that are costly, or at least costly if untrue.

The figure shows the hypothetical results of an experiment testing for parent-of-origin conflict due to genomic imprinting. Which of the following conclusions is most likely given these results?

There is maternal imprinting but not paternal imprinting

Drag each statement to the correct box to indicate whether it is true or false of haplodiploid genetic systems and eusociality.

True: A father contributes 100% of his genome to each daughter under a haplodiploid system. Males in a haplodiploid system have no fathers. Under a haplodiploid system, females are more related to their full sisters than they are to their daughters. False: In a haplodiploid insect species, both males and females are haploid as larvae but develop into diploids as adults. Because of its effects on coefficients of relatedness between full sisters, haplodiploidy can explain the evolution of all known cases of eusociality.

Drag each statement to the correct box to indicate whether it is true or false of how costly signaling explains the maintenance of begging behavior in baby birds.

True: Begging will impose some fitness cost (e.g., in terms of energy and/or predation risk). Parents will deliver more food in response to more intense begging. Begging intensity will accurately reflect hunger level. False: Parents will assess nestling hunger level independent of their begging behavior.

Drag each statement to the correct box to indicate whether it is true or false of eusociality.

True: Eusocial animals show cooperative care for young. In a eusocial species, some individuals forgo reproduction and perform other tasks such as foraging or defending the colony. False: Eusocial species have nonoverlapping generations. Eusociality can evolve only in animals with a haplodiploid genetic system.

Drag each statement to the correct box to indicate whether it is true or false of begging behavior according to the graphical model in the figure.

True: For starving offspring, the benefit of calling outweighs the cost. The cost of begging outweighs the cost to a satiated offspring. False: The optimal begging intensity is lower for a starving offspring than for a hungry offspring because a starving offspring does not have adequate energy to sustain high levels of calling.

Drag each statement to the correct box to indicate whether it is true or false of the hawk-dove game as a model of animal conflict. Assume that there are cues that allow individuals to know who is Player 1 and who is Player 2.

True: If the cost of injury exceeds the value of the resource under dispute, there is a Nash equilibrium when Player 1 always plays H and Player 2 always plays D. If the value of the resource under dispute exceeds the cost of injury, there is a Nash equilibrium when both Player 1 and Player 2 always play H. False: If the value of the resource under dispute exceeds the cost of injury, there is a Nash equilibrium when Player 1 always plays H and Player 2 always plays D.

In the desert seed harvester ant, Messor pergandei, two or more unrelated queens cofound each nest, and each founder produces about the same number of offspring. The number of cofounders is positively correlated with the number of workers that the colony initially produces, and colonies with more workers have better defenses against colony-destroying brood raids. Initially, the founding queens of a colony do not form a dominance hierarchy, but there is a shift toward antagonistic behavior, including fights to the death, once the workers emerge. Examine the graph and drag each statement to the correct box to indicate whether or not it is a valid conclusion about the evolution of queen behavior in these ants.

True: Selection among nests favors cooperation among queens at the time a colony is founded. The colony-level benefits of cooperation decline after workers have emerged. False: Cooperation is favored by within-group selection before workers eclose but is favored by between-group selection after workers emerge. Within-group selection dominates before workers emerge, and between-group selection dominates after eclosion.

Drag each statement to the correct box to indicate whether or not it is a conclusion that follows from the results in the graph.

True: Signals that overstate fighting ability prompt social punishment. Facial markings in paper wasps are conventional signals of fighting ability. False: Any signal that misrepresents fighting ability prompts social punishment.

Drag each statement to the correct box to indicate whether it is true or false of signaling involved in social interactions.

True: The mind reading versus manipulation view of communication invokes antagonistic coevolution to explain the evolution of signals. Social punishment has been implicated in the maintenance of honest conventional signals of fighting ability in house sparrows and paper wasps. False: Costly signaling theory assumes that honest signals impose a higher fitness cost than dishonest signals.

Drag each statement to the correct box to indicate whether it is true or false of the tug-of-war model for the evolution of genomic imprinting.

True: The model predicts that a male should be selected to divert more resources to his current offspring than is optimal from the perspective of his current female mate. The "tug-of-war" for which this model is named occurs between a female that is equally related to all offspring she will produce in her life and a male who is father to her current offspring but not necessarily to her future offspring. False: In mammals, the father is more closely related to any given current offspring than is the female with which he sired that offspring. In mammals, maternally imprinted genes are typically associated with allocating resources toward increasing embryonic growth rates, whereas paternally imprinted genes are typically associated with decreasing embryonic growth rates.

Drag each statement to indicate whether it is true or false of the relationship among signal level, fitness gain, and fitness cost as shown in the graph.

True: The optimal signal level for a poor fighter is lower than the optimum for a good fighter because there is a negligible fitness cost associated with deception. A greater signal level indicates greater fighting ability, and greater fighting ability is associated with higher fitness, presumably via privileged access to resources. False: As the signal level increases, the cost of the signal decreases.

Drag each statement to the correct box to indicate whether it is true or false of game theory models of reciprocal altruism.

True: The prisoner's dilemma is a game theory model used to explain how cooperation could evolve as a consequence of reciprocal altruism. In game theory, a Nash equilibrium is a pair of strategies in which neither player benefits by changing strategy. False: When applying game theory to the evolution of social behavior, an evolutionarily stable strategy is the same as a strict Nash equilibrium. In a single round of the prisoner's dilemma game, there is a Nash equilibrium when both players cooperate.

Imagine a model in which the players in a hawk-dove game do not know who is Player 1 and who is Player 2 and the cost of injury is higher than the value of the disputed resource. Drag each statement to the correct box to indicate whether it is true or false of the Nash equilibrium associated with this game.

True: There is a mixed Nash equilibrium in which each player plays hawk with probability p and dove with probability 1 - p, such that both strategies give the same payoff. There is a mixed Nash equilibrium in which some fraction p of the population plays hawk and a fraction 1 - p plays dove, such that p = v/c. False: There is a strict Nash equilibrium in which both players always play dove.

What is an evolutionarily stable strategy (ESS)?

a strategy that, when common in a population, cannot be invaded by a rare mutant strategy

Which of the following statements is true of information sharing?

an individual can share information with another individual without losing any of the information itself.

Why does the cost-benefit difference decrease for a focal offspring as direct parental investment increases above the optimum level (from that individual offspring's perspective)?

beyond that level of investment, the cost to the parent compromises its ability to invest in other offspring to the point that there is no longer a benefit to the focal offspring in terms of indirect fitness.

An inexpensive signal whose meaning does not intrinsically arise from its structure is which type of signal? Social punishment of deceptive signalers may help maintain honesty in such a communication system.

conventional

Some signals are energetically costly to produce and are thus honest indicators of some inherent quality of the signaler. However, communication can also involve ____signals that are not particularly expensive and convey meanings that do not arise intrinsically from the structure of the signal. For example, male house sparrows bear black patches on their throats as badges of fighting ability, and individuals with signals that overstate their abilities are disproportionately attacked by dominant males who impose _____. Such attacks, which select for ____ signaling, depend on the ability of individuals to directly assess the quality that the signal advertises, for example by engaging in combat with a sparrow to see how well he can fight.

conventional; social punishment; honest

When two animals interact in a way that generates a net fitness benefit for both, we call the behavior ____. To understand the evolution of such social interactions, we need to solve the puzzle of ____ behavior, whereby an individual incurs an immediate fitness cost but increases the fitness of another. Darwin puzzled over how a behavioral trait that benefits other individuals at the expense of the actor could increase in a population via natural selection. We must also establish the conditions under which such seemingly selfless behaviors would be selectively favored over the actions of ____ that receive fitness benefits from social interactions without investing in activities that benefit others.

cooperative; altruistic; free riders

Which of the following statements best explains why the results in the figure suggest kin selection as an explanation for the evolution of alarm calling in Belding's ground squirrels?

females do not disperse from their birth populations, but males do.

Hymenopteran insects have a ____genetic system in which ____ develop from fertilized eggs and ____ develop from unfertilized eggs. One consequence of this genetic system is that a father contributes ____ of his genome to each of his daughters, whereas a mother contributes ____ of her genome. Therefore, full sisters have a coefficient of relatedness ____ that between a mother and a daughter and that of diploid sisters. It is thus common for eusociality to evolve via kin selection in bees, ants, and wasps since "worker" females can potentially maximize their ____ by forgoing their own reproduction and helping to raise their sisters instead.

haplodiploid; females; males; all; half; greater than; inclusive fitness

Which term associated with a behavior is the sum of its effect on the actor's own fitness and its effect on the fitness of genetic relatives?

inclusive fitness

Evolutionary conflict can occur below the individual level when an allele in a heterozygote generates a bias that causes it to be represented in more than half of the individual's gametes. The process whereby this biased distribution happens is called _____. Another form of conflict within an individual's genome occurs when there is _____, whereby specific alleles inherited from either the father or the mother are modified such that the parent from whom a chromosome originated determines gene expression and function.

segregation distortion; genomic imprinting

coefficient of relatedness

the probability that an allele in one individual is identical by descent to a copy of that allele found in a second individual

When does the prisoner's dilemma game predict that cooperation will be an advantageous strategy?

when the game is iterated and there is uncertainty as to the number of rounds two interacting individuals will play against each other.