Chapter 12: Principles of Social Evolution Flashcards
Describe group living in termites
a huge number of tiny STERILE termites build a huge home for their 1 REPRODUCING QUEEN AND ONE KING.
Phenomenon that allows the sterile tiny termites to built a home for the one queen and one king.
EUSOCIALITY: small number of reproductive individuals being helped by a bunch of sterile individuals.
Why are eusocial groups even favored by natural selection?
sterile individuals often are related to be the reproductive members, so it does STILL GIVE THEM REPRODUCTIVE SUCCESS.
Living in a cooperative group in which usually one female and several males are reproductively active and the nonbreeding individuals care for the young or protect and provide for the group
Eusociality. focuses on that non-breeding individuals/sterile individuals still get reproductive success by helping becasue they are related to the fertile insect/animals.
eusociality often results in the evolution of a ___ system. What does this result in?
CAST SYSTEM. results in different morphological differences in members of the population (soldiers, queens etc).
Outline the 7 major evolution transitions
1) replicating molecules to populations of molecules in compartments
2) independent replicators to chromosomes
3) RNA as both genes and enzymes to DNA and protein
4) prokaryotes to eurkaryotes
5) asexual clones to sexual populations
6) protists to multicellular organisms
7) solitary individuals to colonies with nonreproductvive CASTES (EUSOCIALITY)
8) primate societies to human societies.
3 key features to all major evolutionary transitions
1) a transition of independent replicators to higher-level evolutionary units
2) the emergence of DIVISION OF LABOUR that allows greater efficiency
3) the emergence of NOVEL INHERITANCE SYSTEMS that allow information to spread.
What is altruism
behavior that benefits others at a cost to the individual performing the behavior.
T/F cowbirds are altruistic
false. they are considered to be a selfish species.
provide an example of altruism in honey bees
a worker bee provides a suicidal sting to an enemy when there is an invader.
example of altruism in eusocial an species
in colobopis saundersi, the soldier ants store a quantity of mucus glue-like substance. when they’re approached by a predator, the soldier goes out and explode themselves to release glue onto the predator.
Wynne-edwards theory of group selection
groups or species with self-sacrificing (altruistic) individuals are more likely to survive than groups without altruists, leading to the evolution of GROUP-BENEFITTING ALTRUISM. Basically “for the good of the group”
Has been discredited because suicide on an individual level would be selected AGAINST by natural selection, even if it were beneficial to the group or species as a whole.
Wynne-edwards suggested that individuals self-sacrifice “for the good of the species,’ whereas George williams agrued that:
Traits spread for individual advantage or FAMILIAL advantage, but not for the entire good of the species.
The presence of a hereditary trait (including a behaviour) and of the genes underlying the development of that trait, was much more likely to be determined by differential reproductive success of genetically distinct individuals instead of genetically distinct groups (altruistic vs not altruistic groups)
Williams argued that individual level selection trumped group level selection
weakness of group selection
williams pointed out that the weakness of group seelction was that it undermined CHEATING. The genes of selfish individuals who cheat will be disproportionaly represented in groups of altruists because the cheaters (not as altruist) will most likley be the ones to breed if the others are self-sacrificing.
Ex/ seabirds lay only one egg. People thought this was done for the good of the group because these seabirds are still able to take care of two babies if you place another egg in the nest.
It is actually in their self interest to raise one chick at a time because it is really hard to raise two puffins at once, often resulting in death of the parents.
T/F: group selection theory (wynne-edwards) can explain lion infanticide
false. Group selection cannot explain why male lions kill cubs that aren’t theirs. This does not benefit the entire species.
If group selection was true, the male lions should kill all cubs indiscriminately in order to REDUCE STRESS ON RESOURCES, but they keep their own cubs alive. This Is a selfish phenomenon
Hamilton’s theory was based on the premise that some species demonstrate altruism or eusociality beause relatives tend to:
share genes by recent common ancestry. Personal reproduction results in DIRECT selection, but assisting close kin other than one’s own offspring is an INDIRECT route to the same end: propagating identical genes.
what does the coefficient of relatedness refer to?
r refers to the probability that an allele in one individual is present in another because both individuals have inherited it from a recent common ancestor
r of siblings
0.5
r of half siblings
0.25
r of cousins
0.125
r of aunts or uncles to their neice or nephew
0.25
direct fitness
fitness gained through personal reproduction
indirect fitness
fitness achieved by helping nondescendent kin survive and reproduce
inclusive fitness
a sum of an individuals bot direct and indirect fitness. a total measure of an individuals contributions of genes to the next generation generated by both the direct and indirect fitness.
kin selecion
a type of natural selection that favors the reproductive success of the relatives an organism helps, even at a cost to the organism’s own fitness.
in order for an altruistic trait to be adaptive, the inclusive fitness of an altruistic individual has to be greater than:
it would have been if those individuals had tried to reproduce personally.
Hamilton’s rule:
rB>C
r= relatedness
B= benefit
C= cost
explain brood parasite birds in terms of why they are selfish using hamiltons rule
We expect selfishness in brood parasites because there are no fitness benefits to their sbilings/recipients because there are no degrees of relatedness.
Therefore, altruistic behavior is more likely across closely related relatives.
_____ selection encompasses both kin/individual and group selection
MUTLILEVEL SELECTION.
some people didn’t fully agree with kin selection because they thought there were some situatoins in which group seelction could still apply. Multilevel selection explain these “exemptions,’ such as the fact that insect colony members benefit when there are a more altruistic members of the group (group selection tendency), but also accounts for relatedness playing a factor in how altruistic someone is.
What is multilevel selection
colonies with more self-sacrificing individuals will be favored by group selection if groups with more altruists OUTCOMPOETE RIVAL GROUPS AND CONTRIBUTE MORE GENES to the next generation.
-encompases both individual and group-level selection. Ie, selection may occur simulatneously at the level of the group AND the level of the individual: the outcome will depend upon the strength of selection at the different levels.
Multi-level selection can occur in the level of species, groups within species or individuals. There may often be conflcit within genes in an individual itself.
haplodiploidy
a SEX-DETERMINATION SYSTEM in which males are haploid and females are diploid.
explain haplodiploidy in hymenoptera wasps
males are haploid and possess only one set of chromosomes because of parthenogenesis (development from an unfertilized egg)
females are diploid, developing from fertilized eggs.
in haplodiploidy species, what happens to the degree of relatedness of the offspring relative to each parent?
because males are haploid, all their sperm is GENETICALLY IDENTICAL.
in a female , all the sperm she receives will have the same set of genes: her daughters will carry identical sets of paternal genes (100% of dad), but will share only 50% of maternal genes. Therefore, daughters are 50% related to their father and 25% related to their mother, for a total of 0.75.
Therefore, sisters are more related to each other (0.75) than they are to their mother.
how does haplodiploidy set the stage for altruism
sisters are related to each other by 0.75, rather than 0.5.
in haplodiploidy species, what the degree of relatedness between sisters? brothers and sisters? mothers and daughters?
Sisters share UP TO 75% of their genes
Mothers and daughters share 50% of their genes
Brothers and sisters share 25% of their genes
haplodiploidy hypothesis
the relatively higher relatedness of full sisters in haplodiploid populations promotes altruism among siblings, and, consequently, the evolution of eusociality.
according to the haplodiploidy hypothesis of eusociality, female worker hymnoptera should help which siblings?
female workers in ants should help their reproductively competant SISTERS and not brothers because they are up to 0.75 related to females, but only 0.25 to their brothers.
a worker bias in favor of sisters would also bring workers into conflict with their mothers, because mothers (queens) are equally related to sons and daughters.
Explain the works of bob trivers and hope hare on haplodiploidy
they argued that because sisters are three times more closely related to another than they are to their brothers, wasps should invest three times as much in their sisters than their brothers.
the combined wieght of all the adult females (a measure of the total resources devoted to the production of females) should be three times as much as the combined wieight of all the adult male reproductives.
They noted that workers maintain some level of control over offspring production. If queens had full control, you’d expect a 1;1 ratio because they are genetically related to their sons just as much as to their daughters.
two problems to the haplodiploidy hypothesis
1) it doesn’t explain all eusociality- ex/ termites are diploid
2) haplodiploidy works best with monogamy; but many eusocial hymenoptera are polyandrous, lowering relatedness among workers.
what is the monogamy hypothesis?
the idea that lifetime monogamy ensures that siblings are highly related, making it evolutionarily adaptive to be an obligately sterile worker, and ultimately making eusociality able to evolve.
most eusocial insects are ___ ___. Why is there no incentive for worker insects to go start their own colony?
most eusocial insects are FAMILY GROUPS. If the sterile workers of one family are helping in ways that benefit the entire colony, the fact that their reproducing relatives are present means that sterile individuals CAN GAIN FITNESS benefits from the enhanced output of reproducing relatives
there is no incentive for worker insects to go start their own colony because they must survive to reproduce. There is no incentive for worker insects to go out and start their own colony if they are gaining INDIRECT FITNESS ADVANTAGES from helping their siblings survive to reproduce.
T/f: in the case of hymenoptera, polyandry evolved from monogamy
true. all these groups of wasps and ants started off as monogamous. Therefore, monogamy is linked to eusocial behavior.
a defining characteristic of eusocial societies is a ______ ___ ___ ___
reproductive division of labour, or the PRESENCE OF CASTE SYSTEMS
in all eusocial species, there is a ___ ____.
REPRODUCTIVE CASTE: a queen or queens, and sometimes a king, and the rest tend to be of the worker caste who forage, take care of young, and perform other colony work.
Castes in harvester ants
there is a large queen, a major worker, a minor worker.
some other castes have soldier castes
explain worker policing in eusocial insects.
workers and the queen monitor the reproductive behavior of others. Being sterile might actually not be voluntary.. Eggs laid by individuals other than the queen will usually be eaten by other colony members.
what is reproductive conflict
encompasses not only conflict over which individuals get to breed, but also the battle over the resources that individuals need to breed.
outline reproductive conflict seen in ant colonies.
individuals that are about to reproduce are detected by colony-mates and physically prevented from doing anything for hours or days.
The queen smears the ant in the center with her sting. Three workers grasp the would-be reproductive ant from moving.
After holding her captive for 3 or 4 days, a worker may turn her prisoner over to another worker to continue imprisonment.
the percentage of reproducing workers in the nests of social wasps ____ as the effectiveness with which their fellow workers destroy their eggs increasese.
the percentage of reproducing workers in the nests of social wasps DECREASES as the effectiveness with which their fellow workers destroy their eggs increases.
if worker policing is responsible for reducing the number of workers’ songs, then in cases with low number of worker sons, the policing workers are:
the policing workers are MORE CLOSELY RELATED TO THE QUEENS SONS THAN OTHER WORKERS SONs.
the greater the difference in the relatedness of worker’s and queens sons, the greater the proportion of males that are produced by:
workers. ex/ the queen would be “more okay” with workers reproducing if they shared more genes with the potential offspring.
kin selection vs group selection
kin selection theory has been used to make testable predictions about the kinds of conflicts likely to occur in colonies.
group selection is better at explaining altruism than conflict.
