Lecture 9: Human and animal Flashcards Preview

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Flashcards in Lecture 9: Human and animal Deck (24):

What is the term for a behaviour where both participants benefit?
What about if only you benefit?
Only they benefit?
No one benefits?



What is the main problem of group living?

Free-riders. For example, a vervet monkey that doesn't produce its share of alarm share. According to natural selection, free riders should prosper. However, they tend not to, so its the central problem of sociobiology according to Wilson.


Describe the different levels of selection

Selection of groups: Wynne-Edwards did a study on animal dispersion in relation to social behaviour and found that animals modify their behaviour for the good of the group, for example, controlling population density or competition of resources. Therefore a group of animals are more likely to survive and the selfish individuals wouldn't. This makes theoretical sense.
Selection of individuals: Williams researched adaptation and natural selection and found that selfish individuals take more than their fair share of resources and therefore have increased fitness, over time the whole group would become selfish, conditions aren't likely to favour the group over the individual.
Selection of genes: Gene are immortal coils whereas bodies are impermanent so a selfish gene is more likely to spread through the group.


Does the selfish gene lead to selfish animals?

No, selfishness and altruism are both widely spread throughout the population. Examples of altruism: Parental care, sharing food, alarm calls and alliances.


Discuss relatedness/gene's point of view

In diploid species, a gene has a 50% chance of being passed on to an offspring. Animals can act in a certain way to ensure that their genes are passed on or their relatives have a greater chance of survival, e.g. ants. Siblings have 0.5 relatedness, grandchildren 0.25 and cousins 0.125.


What is Hamilton's rule?

An altruistic gene would spread if rB>C where r=relatedness, B=benefit and C=cost. It would also spread if rB-C>0. Or if B/C>r donor to own offspring/r donor to recipient's offspring.


What did Hoogland 1983 find about alarm calls in prairie dogs?

They are more likely to produce an alarm call if close relatives are in the social group.


What is Hamilton's rule?

The idea that it's more beneficial for brothers to have the same polyandrous female, this is quite common in nature, especially with native hens. It's more beneficial as selection could favour them however it wouldn't for unrelated polyandrous couples. Also, there is an increased chance for reproductive success and more chance for their genes to be passed on in comparison to monogamous couples.


Define kin selection

When a (disadvantageous) characteristic spreads through the population, like altruism, because of increased survival of those who are genetically related.


Define relatedness

The probability that individuals share a rare gene that is identical by descent. Kin selection favours these genes over those that aren't identical by descent.


Describe the cooperation of social insects

They cooperate by having sterile worker castes, however this is a Darwinian problem as it goes against natural selection. This cooperation is a form of eusociality, there's a reproductive division of labour, cooperative care of young and overlapping generations. The insects repeatedly evolve independently.


Social insects are also called superorganisms, compare these to individual organisms

Individuals: Organs, foraging, reproduction, defence.
Superorganisms: Caste system, workers, queens, soldiers
Individuals: Germ line and soma
Super: Queens and workers
Individuals: Information sharing, functional dependency, immune system
Super: Nervous system, need each other to survive, rejection of invaders.


Describe the lifestyle of hymenopteron

The queen hibernates in the winter, then she forages, the she starts nest initiation, she then produces workers and develops the colony, mating then occurs, the males die and the queen is left to hibernate again.


Describe how you work out relatedness
Describe the relatedness/haplodiploidy of hymenoptera

Make a flow chart and follow the lines, each split, divides the relatedness by half (except for haplodiploids).
Sisters are related to each other by 0.75 but are related to their brothers 0.25. They are related to their daughters 0.5 and nephews 0.375.


How did eusociality evolve?

Because natural selection favours the sister's involvement in her mother's reproduction rather than her own as sisters are more related to each other than daughters. Perhaps haplodiploids have a genetic predisposition for eusociality, however this is too simplistic. Perhaps because of ecological constraints, for example, so they could defend their young from parasites by building a nest.


Discuss the conflict of interest in haplodiploids

There is a worker-worker conflict over male production. Sometimes workers are fertile and produce unfertilised eggs/males. The queen prefers the production of sons as she is more related to them compared to daughters. However, the reproductive workers prefer sons to brothers so this is a conflict and the sterile workers prefer nephews to brothers. This all relates to relatedness. So when the queen bee is reproducing and she switches from diploids to haploids, the workers start laying their own eggs and sometimes commit matricide (kill the queen). Furthermore, multiple mating reduces the relatedness of sisters so workers care for full sisters but kill half sisters. Multiple matings also reduces the relatedness of nephews. However the queen labels her eggs to reduce the conflict of interest as this makes it evolutionarily stable.


Describe eusocial mammals

Naked mole rats are eusocial mammals. They live in the desert in East Africa. There are up to 80 individuals but there's only one female. The rest are workers and provision the young. The queens bullies the lazy workers and they have no ovulation and increased stress hormones. The relatedness in these colonies are high due to inbreeding.


Give 2 examples of cooperation without relatedness

Some animals display non-altruistic behaviour that is still cooperative. For example, mutualism like cooperative hunting or lichens. Also, manipulation like brood parasites (cuckoo birds).


Discuss the prisoner's dilemma

It's the concept that if both you and your accomplice cooperate with each other (R) when being questioned then you will get a light sentence. If you defect and they cooperate (T) then you go free. If you cooperate and they defect (sucker's payoff (S)) then you get a heavy sentence. If there is mutual defection then you get a medium sentence (P). T>R>P>S. However, R>(S+T)/2. Therefore, it is always best to defect as there is a chance you could get off free and if you didn't, the sentence would only be medium, this isn't the optimum option but it's a Nash equilibrium.


Describe the evolution of reciprocity

If defection is stable then why would there altruistic behaviours? Trivers 1971 found that altruistic behaviour is selected if it's repaid at a later date, aka a non zero sum game. Axelrod 1984 found that with the prisoner's dilemma, the best strategy was this tit for tat strategy. This involves cooperating at first and then after this, doing whatever the partner did. This strategy is optimistic, retaliatory, forgiving and non-envious. It can be evolutionarily stable, especially if repeated interaction is high. Tit for tat starts via spatial association leading to the green beard effect (altruistic animals group) which involves kin selection and reputation.


Give examples of reciprocal altruism

Wilkinson 1984 found that vampire bats regurgitate blood to give to a donor that is close to starvation. The donor will then repay this favour at a later date, this is regularly repeated and the donor and recipient roost together.
Primates grooming each other, this is an affinitive behaviour and forms alliances between unrelated monkeys. Baboons have sexual alliances, the males take turns.


Describe the evolution of ethics

It's shaped by reciprocal altruism and has formed societies, morals and emotions. For example, optimism, retaliatory, forgiving and non-envious can relate to gratitude, friendship, morals, forgiveness and honour.


Describe the evolution of spite

It starts with negative relatedness which is when two individuals are less related than average.


Finish the sentence
Kin selection can explain altruism between...
Reciprocal altruism can explain altruism between..

... related individuals as it can benefit them more by ensuring their relatives have increased fitness compared to benefiting their own fitness.
... unrelated individuals.