Dawkins Behavioral Ecology Quiz

What is wrong with the argument that traits evolve for the good of the group or the species?

Traits do not evolve "for the good of the group" because natural selection acts primarily on genes and individuals, not on groups. A trait that benefits the group but reduces an individual's reproductive success will be eliminated, since selfish individuals within the group will gain an advantage and outcompete altruists. Selection within groups is typically faster and stronger than selection between groups. Even hypothetically 'pure altruist' groups would see selfish individuals migrate and reproduce, thus contaminating the gene pool. Selfish individuals prosper in short term at the expense of the altruists.

Does evolution work more rapidly between competing groups or between competing individuals?

Evolution works more rapidly between competing individuals (and genes) than between competing groups. This is because individuals reproduce and die on much shorter timescales, so indvidual selection is faster and stronger than group selection. Any group-level advantage is usually undermined by selfish individuals within the group who leave more offspring. As a result, individual-level selection typically overwhelms group-level selection.

What is natural selection?

Differential Selection that is based on variable fitness. Some genes are better at producing survival machines that continue to persist. Several traits make the organism have higher fitness and it'll become numerous across organisms in generations

Outline the evolutionary argument for senescence.

The genes that are harmful that show up in old age don't affect the reproductive fitness of the organism so they get passed on and are not selected against. Those harmful genes are therefore passed on to future generations. Basically, selection is stronger at younger ages especially if expressed after reproduction

What are the evolutionary costs and benefits of sex?

Costs: inefficient way of propagating genes in that each child has only 50% of a parent's genes. It is easier to think of group-level advantages to sex, which could lead one to believe in group selection.

Benefits: sex facilitates the accumulation in a single individual of advantageous mutations which arose separately in different individuals, which creates genetic diversity. The gene pool is kept well-stirred, and the genes partially shuffled.

How do genes influence behavior?

Gene influences behavior indirectly by building brain and nervous systems that respond flexibly to environments. This determines organisms fitness that could be passed to future generations

Why should an individual refrain from a fight to the death?

An individual should refrain from a fight to the death because natural selection favors strategies that maximize long-term reproductive success (not winning at all costs). A fight to the death carries a high risk of injury or death, which would eliminate all future reproductive potential. Evolution therefore favors threat displays that resolve conflicts while minimizing harm. Individuals that escalate only when the expected benefits outweigh the costs leave more descendants.

Other rivals may be more likely to benefit from this death than the individual itself. In large complex societies, removing any one rival may not do any good - other rivals may also benefit.

When are fights to the death most likely to occur?

Fights to the death are most likely to occur when the resource being contested is extremely valuable, or when there is little chance of future opportunities. This could happen when there is asymmetrical fitness. It could also happen when resources are very scarce (ex. very few mates around). In these situations, the potential benefits may outweigh the high costs of escalation.

What is an evolutionarily stable strategy?

An evolutionarily stable strategy (ESS) is a behavioral strategy which, once common in a population, cannot be invaded by an alternative strategy. The best strategy for an individual depends on what the group is doing. Selection will penalize deviation from it. If a rare mutant does worse when interacting with the dominant strategy, natural selection will eliminate it. An ESS therefore represents a stable outcome of natural selection.

When will hawks not drive doves to extinction?

The hypothetical situation of there being one dove in a population of Hawks shows us that it is unlikely that doves are driven to extinction. This is because the dove will never be seriously hurt in an encounter while one hawk per hawk-hawk encounter will be hurt. Thus, the Dove's genes will spread through the population..

If hawk and dove coexist at an ESS what would have higher fitness, a new baby with hawk or dove genotype? Discuss.

If hawks and doves coexist at an evolutionarily stable strategy, a new baby with either a hawk or a dove genotype would have equal fitness. The stable ratio of hawks to doves is 7:5. Depending on the proportions of each in the coexisting group of hawks and doves, one genotype will have a higher fitness. This is because, at an ESS, all strategies present yield the same average payoff; if one had higher fitness, it would increase in frequency and disrupt the equilibrium.

What is a conditional strategy?

A conditional strategy is a strategy of behavior n which an individual's behavior depends on circumstances, such as the opponent's behavior, relative strength, or ownership of a resource. Rather than being purely hawk or dove, individuals follow rules like "escalate if you are the owner, retreat if you are the intruder." Conditional strategies can be evolutionarily stable because they tailor behavior to maximize fitness in different situations (ex: Retaliator/bully)

What do aphids do that armadillos don't? Why?

Aphid altruism has been discovered. Groups of aphids are genetically identical clones, but some environmental factor makes them take on different roles. The benefit of rapid reproduction greatly exceeds the cost of reduced genetic variation, so Hamilton's rule (rB > C, with r = 1 for clones) is easily satisfied. There are sterile "soldiers" who altruistically fight off predators from their genetically identical non-soldier counterparts. Even if the soldiers can not reproduce, it doesn't matter since their siblings probably can.

This altruism phenomenon has not been observed in armadillos, which are born in litters of identical quadruplets (clones).
Both species clone themselves, but Aphids cooperate because there can be kin selection.

What are the pros and cons of an adult male baboon defending babies against a leopard?

The benefit of an adult male baboon defending babies against a leopard is that he may be protecting his own offspring or close kin, thereby increasing his inclusive fitness. The cost is a high risk of injury or death, which would eliminate future reproduction. Such defense is favored by natural selection only when the expected genetic benefits (through related offspring or future mating advantages) outweigh the personal survival costs.

When are eggs recognized and when not?

Eggs are recognized when there is a tendency for eggs to roll or end up in another nest. Mothers don't want to waste energy rearing someone else's offspring. This is when the cost of mistakenly rejecting one's own egg is low and when parasitism is common.

They are not recognized when it is unlikely for eggs to end up in a different nest than its own. Recognition errors would be very costly (e.g., rejecting one's own offspring)

How do cuckoos get away with their parasitism?

Cuckoos exploit the rule built into bird parents: "Be nice to any small bird sitting in the nest that you built." This is due to the fact that nests are so isolated from each other that the contents of your own nest are almost bound to be your own chicks. They also succeed because their eggs closely mimic the host's eggs, reducing the chance of rejection. Hosts may tolerate cuckoo eggs because the cost of rejection mistakes outweighs the cost of raising a parasite. Most types of birds that cuckoos interact with do not recognize eggs because there is no need to as described above.

Compare egg recognition in gulls and guillemots.

Gulls do not recognize eggs because it is very improbable for a gull egg to move from one next to another since they are far away and high up. They will sit on other eggs. They are able to recognize their own chicks however.

Guillemots do recognize eggs because their eggs can easily roll around to nearby nests. They reocgnize their own eggs by the speckling pattern and will actively discriminate in favour of them when incubating. They nest on flat rocks, where there is a danger of eggs rolling around and getting muddled up

Why do lower-ranking individuals have a lower chance of reproducing?

Reproducing in nature often depends on controlling a territory and thus attracting a mate. Low-ranking individuals who fail to control a territory by losing competitions have less chance of attracting mates. Also, high ranking males can physically prevent other males from even approaching females. Dominant individuals monopolize resources, mates, and breeding opportunities.

What is the Lack hypothesis? Why was David Lack so important in early thinking about selfish genes?

The Lack hypothesis states that clutch size evolves to maximize the number of surviving offspring, not the number of eggs laid. In any given enviromental situation, there must be an optimal clutch size that maximizes the number of children reared. Producing too many offspring reduces survival due to limited resources.

Lack was important because he framed reproduction in terms of individual-level optimization, paving the way for later gene-centered thinking central to Dawkins' argument. This helped with the idea that selfish gene theory would have a goal of laying the optimal point of eggs over just as many eggs as possible.

What factors might favor producing fewer eggs than one could rear to independence?

Producing fewer eggs may be favored when parental survival affects future reproduction, when high investment per offspring increases offspring quality, or when environmental conditions are unpredictable. Laying fewer eggs can preserve the parent's condition and allow greater lifetime reproductive success, rather than maximizing output in a single breeding attempt.

When do animals reduce their clutch size? Which babies are they likely to remove, largest or smallest?

When resources are scarce, instead of struggling to provide for many, the mother may choose to reduce the clutch, so that they can feed each child enough to survive. They tend to remove smaller offspring, which are less likely to survive and end to need more food and care.

Basically if cluch size goes down, this is likely so the bird can up the investment in each: this will up the chance of getting offspring that will reproduce.

If siblings are related to each other why should they be in conflict?

Siblings should be in conflict because, although they are related, they are not genetically identical. Parents have a finite amount of time, energy and resources to invest in their offspring. Thus siblings are in direct competition for these resources, and any resources that an individual obtains lowers their siblings share of resources.

Why and when should a mother have favorites? Is a short-lived mother more or less likely to have favorites than is a long-lived mother?

There is no genetic reason for a mother to have favorites, but she could show favoritism based on the differential life expectancy of her offspring.

It may pay a mother to refuse to feed a runt and allocate all of his share of her parental investment to his brothers and sisters. It may pay her to feed him to his brothers and sisters, or to eat him herself and use him to make milk.

If a mother has to pick one child to save out of two, and the one who she doesn't save will definitely die, it would be more wise to pick the older child who she has already devoted more resources to. If the situation is not life or death and she is deciding whether to feed a morsel of food to a younger or older child, she might choose the younger child instead because it is more likely to die because it is less able to find food for itself.

A short-lived mother is more likely to have favorites because she has fewer future reproductive opportunities and should invest heavily in the best current offspring, whereas a long-lived mother can spread investment more evenly across multiple breeding attempts.

Are runts evolved, or developmental accidents? Why or why not?

Runts may have evolved as a sort of insurance policy for the mother, one that she initially doesn't invest much into but if something happens to her other offspring, she can reinvest in the runt.

She can also easily ignore him if and use him to feed her other offspring if resources are scarce. (Runts evolved because runts are animals smaller than rest. Runts are unable to get food; if mom has extra child and realizes food crop is good, mom will rear extra child. if not, will cut losses. so runts are a result of mom deciding what is best based on optimal clutch?)

Who wins parent-offspring conflict and why? What are the important variables?

Neither parent nor offspring always "wins" parent-offspring conflict. The outcome depends on which strategy maximizes gene replication.

Offspring are selected to demand more parental investment than is optimal for the parent, because each offspring is more related to itself than to its siblings. Thus they may try to deceive the parents by lying and saying they're hungrier than they are.

Parents are selected to limit investment to preserve resources for current and future offspring. Since they are larger and the ones who actually hunt for food, they are in a position to decide whether or not to feed an offspring extra. If it decides to withdraw, the child can't do much.

Overall, parents are bigger and stronger, but the young have a few good tricks too. They are in a position to lie and the parent can only guess if it's telling the truth or not. What will emerge is a compromise between the ideal situation desired by the child and that desired by the parent.

When would a young animal prefer to die than to increase risk to siblings?

As soon as a runt becomes so small and weak that his expectation of life is reduced to the point where benefit to him due to parental investment is less than half the benefit that the same investment could potentially confer on the other babies, the runt should die gracefully and willingly.

Use Hamilton's rule to express the area where mothers and progeny are in conflict

Relatedness of mother and progeny)X(Benefit to Progeny) < (cost to mother)
Rb < C

If relatedness is greater than the cost, then... (how valuable are your relatives to you? Depends on how closely related they are to you)
Kin will want to give less resources when the cost is more than the relatedness
Normally, parental care for yourself over parental care for your siblings
However, consider older sibling (would benefit more to help sibling at times)

(Relatedness of mother and progeny)X(Benefit to Progeny) < (cost to mother). If (R)x(B) is greater than the cost to the individual, kin altruism prevails.

Use Hamilton's rule to express the area where siblings are in conflict with each other.

(Relatedness of siblings)X(Benefit to other siblings) < (cost to first sibling)

What is wrong with Alexander's argument about parental control? When are parents likely to win?

A gene that made a child grab more than his fair share when he was a child, at the expense of his parent's total reproductive output, might indeed increase his chances of surviving. But he would pay the penalty when he came to be a parent himself, because his own children would tend to inherit the same selfish gene, and this would reduce his overall reproductive success. Therefore the genes cannot succeed, and parents must always win the conflict.

Dawkins argues that this argument rests on the assumption of a genetic asymmetry which is not really there. Alexander is using the words 'parent' and 'offspring' as though there was a fundamental genetic difference between them. As we have seen, although there are practical differences between parent and child, there is no fundamental genetic asymmetry. The relatedness is 50%, whichever way you look at it. If you switch the words parent and juvenile in Alexander's argument, you arrive at the opposite conclusion that the child always wins.

Parents are most likely to win when they have low certainty of relatedness, many future reproductive opportunities, or when the cost of extra investment to the parent is very high. In these cases, selection favors strong parental resistance to offspring demands.

What is Fisher's argument for equal investment in the sexes?

The strategy of producing equal numbers of sons and daughters is an evolutionarily stable strategy (ESS), in the sense that any gene for departing from it makes a net loss. This is true even when few males are needed for reproduction, because then it becomes more beneficial to have males than females, and the sex ratio shifts back to equilibrium (because it would first shift to too many females).

What is the difference between investment in males and females, and numbers of males and females?

Parents should invest equally in males and females, because they as individuals have no control over the actual amount of sons and daughters they produce. Normally the amount invested in each son will roughly equal the amount invested in each daughter, and the sex ratio, in terms of numbers, is usually one to one.

How does parental care influence the sex ratio?

The more investment a parent puts into one gender, the more likely the sex ratio swings in favor of that gender. There could be unequal sex ratios that were evolutionarily stable, provided correspondingly unequal amounts of resources were invested in sons and daughters.

ex. elephant seals, a policy of having three times as many daughters as sons, but of making each son a supermale by investing three times as much food and other resources in him, could be stable.

Why do female mice evolve to abort when they smell a new male?

NS would severely penalize such gullibility in males and indeed would favour males who took active steps to kill any potential stepchildren as soon as they mated with a new wife. This is very probably the explanation for the so-called Bruce effect: male mice secrete a chemical which when smelt by a pregnant female can cause her to abort. She only aborts if the smell is different from that of her former mate. In this way a male mouse destroys his potential stepchildren, and renders his new wife receptive to his own sexual advances.

If one parent deserts should the other stay and rear the babies? Why or why not?

Assume the deserted female cannot fool a new male into adopting her child. If the child is very young or hasn't been born yet, it might pay to abort or kill the child and find a new mate.
If the child is already quite old, it might pay to stick it out and try to rear the child on her own. The older he is the more has already been invested in him, and the less it will take out of her to finish the job of rearing him.

A reasonable policy for a female who is in danger of being deserted might be to walk out on the male before he walks out on her, because this can force the second partner into the more drastic decision. Genes for deserting first could be favorably selected simply because genes for deserting second would not be.

The remaining parent should stay only if the fitness benefits of rearing the offspring exceed the benefits of deserting and attempting another breeding.

What is the handicap hypothesis?

False sexual advertisement will eventually be seen through by females. Thus, really successful males will be those who demonstrate they are not deceiving. Costly traits evolve because they act as honest signs of genetic quality. High quality individuals can afford to produce and maintain costly traits, which signals fitness to potential mates. Ex: Birds with peacocks that seems to be a handicap evolve because they are handicaps. It shows these organisms can survive in spite of his tail.

In what sense are ornaments handicaps?

Ornaments are handicaps because they reduce survival by increasing energy costs or predation risk. However, their very cost ensures honesty: individuals that survive despite the handicap demonstrate superior genetic quality. Natural selection can therefore favor such traits through sexual selection, even though they are detrimental to survival.

What sorts of males should females avoid mating with?

Females should avoid males whose traits indicate poor genetic quality or low ability to survive.

They should also avoid mating with males that aren't very sexually attractive (in other words, drab) because this lessens the chances that her offspring will be sexually attractive and pass on her genes. She should also avoid mating with males from closely related species, because her offspring may be hybrid and thus infertile, even if they are viable. Females should also avoid mating with males who don't show long-term fidelity characteristics.

Exactly how can long tails evolve through the process of runaway selection?

Runaway selection was a theory that a trait such as a long tail was a burden to an individual because it made them easier to be caught by predators. Individuals with smaller tails were thought to have had part of their tail bitten off by a predator and individuals with a long tail were thought to be fast and evasive, so they were still around because the predators hadn't been able to catch them. So females would select for the long tail trait and this trait would evolve through generations. But eventually, it overshoots the optimal length as females only select for the trait.

How might we distinguish the runaway selection process from the handicap process?

Runaway selection -natural selection keeps selecting for a trait and shifts average (inrease gene freq.)
Handicap - trait is selected despite its negative effect to show organism survives despite it

Empirically, we can distinguish them by testing whether ornament size reliably predicts viability or survival (supporting handicap) or merely mating success with little link to quality (supporting runaway selection).

Why do fish school? Give two different reasons.

Fish who swim behind another fish may gain a hydrodynamic advantage from the turbulence produced by the fish in front

Fish school because it reduces individual predation risk. Fish in the center of the center of the school, or away from the boundaries, are able to protect themselves from predators.

Schooling improves foraging efficiency by allowing individuals to locate food more effectively. Both benefits increase individual survival without requiring kinship.

How can grouping in the absence of kin selection be advantageous?

Grouping can be advantageous because individuals gain direct selfish benefits, such as reduced predation risk, increased vigilance, or improved access to resources. It uses skills of each other to compensate for weaknesses. Can help with predation as there are more eyes/ears available to look out for predators and warn the others

Why are social hymenoptera sisters related by 0.75?

In social hymenoptera, sisters are related by 0.75 because of haplodiploid sex determination. Females develop from fertilized (diploid) eggs and receive identical genes from their father, who is haploid. If one female has gene A, she must have got it from her mother or father, and if it's from her mother, then there's a 50% chance that her sister shares it. If it's from her father, then there's a 100% chance her sister shares it.

This makes sisters share all paternal genes and, on average, half their maternal genes, yielding a relatedness of ¾.

Why don't slave making ants have female biased sex ratios?

Slave making ants steal offsprings of other ant colonies and raise them to make those ants work for them. Because of this, there is no kin selection advantage to favor sisters over brothers. Thus, the queen is able to get away with counter measures and there is no selection operating on the slaves to neutralize these counter measures as they are not related to the brood. In this case the 0.75 sisters is not true, so they don’t have that benefit of passing their genes. R = 0. R value decreases because they’re not related.

Why might queens of honeybees mate multiply, thereby 'throwing away' the haplodiploid advantage?

So that worker bees will chaperone a queen on her mating flight in order to prevent her from mating more than once. Queens may multiply because it increases gene diversity, and division of labor: these can increase the overall hive work which overrides the disadvantages of doing so.Multiple mating increases disease resistance, and colony stability.

Why is meiotic drive such as is caused by t alleles in mice against the interests of most of the genome?

Because the meiotic drive such as the t alleles cheat inheritance to increase their own transmission while reducing the organism’s fertility and overall reproductive success. They are violate inheritance to ensure their own preferential transmission into offspring

This harms the rest of the genome, which depends on the organism's survival and reproduction for transmission.

Why do flukes cause snails to produce thicker snail shells?

Producing extra-thick snail shells is costly for snails since they will spend less on their offspring in this case. However, flukes benefit from thicker shells, and their genes will exert influences on snail's shell-secreting cells. This benefits the flukes themselves but is costly to snail's genes.

Why do plasmid genes share fewer interests with nuclear genes than nuclear genes share among themselves?

Plasmid genes share fewer interests with nuclear genes because they are inherited independently and replicate asexually and are simply inserted.

Nuclear genes largely share the same fate: they are transmitted together through sexual reproduction, so their interests are aligned. They are tightly packed and need to successfully reproduce in order to pass this gene on. 

What sorts of behavioral information would you want about a parasite to predict its impact on its host's behavior?

The mode of transmission such as lifestyle, the host’s life cycles, how it got infected/how the parasite is transmitted, the reproductive strategy of both because the parasite wants the chance to spread among others. W'e’d also like to know what host behaviors increase parasite replication or transmission. Could do things like making the host go closer to water. Parasite-induced behavior is expected when it increases the parasite's own transmission.

Why would a bird ever feed anyone in a different nest?

A bird may feed chicks in another nest if those chicks carry copies of its genes (kin selection), or if feeding errors are too costly to avoid (mistaken identity). Feeding may also occur when chicks mimic begging signals so effectively that withholding food would risk underfeeding one's own offspring. Selection tolerates such "mistakes" when the cost of discrimination exceeds the cost of occasional misdirected care.

What are the similarities and differences in selection in a pack of wolves and a honeybee colony?

Both wolf packs and honeybee colonies show cooperation (mostly kin selection) because it increases individual genetic success

In wolves, however, cooperation occurs mainly among close kin, and individuals still compete for reproduction. The relatedness to wolves is more like 0.5, but honeybees are 0.75. Many females can breed here.

In honeybees, workers are largely sterile and selection operates primarily through kin selection, with workers maximizing inclusive fitness by helping the queen. Since honeybees have higher relatedness, they take care of each other more, whereas wolves have individual interests conflicts. Only the queen can breed in the colony.

Thus, conflict remains high in wolf packs but is greatly reduced in honeybee colonies due to extreme relatedness and reproductive specialization.