Cooperation II Flashcards
Three key approaches in social evolution
- Inclusive fitness approach
- Neighbour modulated fitness approach
- Multi level (group) selection approach
What is the theory of inclusive fitness?
An organism’s genetic success is believed to be derived from corporation and altruistic behaviour
Direct fitness
Measure of individuals direct reproductive success in passing on genes through offspring production
Indirect fitness
Genes contributed to the next generation by an individual via helping relatives (so indirect because help relatives which then produce offspring - the helper itself doesn’t produce offspring)
Inclusive fitness
The sum of an individuals direct fitness and indirect fitness
What’s an explanation for altruism?
Inclusive fitness - being altruistic and helping others is worth it if it means it can help pass on your own alleles (if u r the same species)
Altruism
Animals help other individuals increase their fitness at a cost to themselves
(Reducing my direct fitness to increase a relatives fitness)
What is Hamilton rule
An equality:
r B < C
r - relatedness
B - benefit to recipient
C - cost to the altruist
What does Hamilton rule tell us?
It tells us when altruism is expected to be selected for in a population
What does relatedness mean in Hamilton rule?
Proportion of alleles shared between altruist and recipient of altruistic behaviour
What does benefit to recipient mean in Hamilton equation
Number of offspring produced by recipient that wouldn’t have been able to be produced without help of altruist
What does cost mean in Hamilton equation
How many offspring the altruist is unable to produce as a result of altruistic behaviour
When does Kin selection occur
When an individuals inclusive fitness is increased by engaging in altruistic behaviour that enhances reproductive success of relatives
What is meant by relative?
Are they more genetically similar than average in the population
Definition of relatedness
Probability
Above average
That actor and recipient share alleles at a focal locus
How closely related are
Clones
Siblings
Half siblings
Non relatives
Clones 1
Siblings 0.5
Half siblings 0.25
Non relatives 0
What is kin selection THEORY
Anything that has a focus on relatedness
Neighbour modulated/inclusive fitness theory
What is kin selection PROCESS
Natural selection involving non zero relatedness
Involving individuals related above 0 - aka so must be clones/siblings/half siblings etc
What is multi level group selection
The help doesn’t go to one specific individual; it goes to a group (which includes the actor - the one giving the help)
Eg. Bacteria makes enzyme that they put out into environment. Enzyme breaks down food so other bacteria can pick up nutrients as well.
Workers raising queens offspring
Q - If we were going to model this what framework would be used?
Inclusive fitness because they are all related
Inclusive fitness is a way to understand social insects
What’s the best way to model the selfishness by transposons as they jump and harm the genome?
Group selection because the genome is a group
Key thing - genome of an organism functions as a group - action of an allele on an organisms is felt by everyone including the gene itself
Best modelling framework for cooperative secretions of bacteria?
Group selection because the secreting cell can benefit AND other cells can benefit form it’s secretions
Best modelling framework for lemmings jumping off a cliff?
XXX
Could use group selection (because lemmings live in groups) or inclusive fitness (because need relatives to benefit form jumping)
Classic model used to study altruism in social insects?
Inclusive fitness
Why can you also use multi level group selection model to study social insects?
Because insects are in groups and you can think about benefits to the colony
Lots of social insect models end up being what
Both inclusive fitness and multi level group selection
Three ways indirect benefits can occur
- Limited dispersal
- Kin discrimination
- Green beard
Explain how indirect benefit occurs through limited dispersal
XXX
44 min 05 don’t get
Bacteria make patches - surrounded by relatives - incentive to cooperate
Example of how local competition could outweigh indirect benefits?
Bacteria in patches surrounded by relatives = gives them more insentive to cooperate
But if they stay localised for too long they might start to compete with their relatives
Why do honey bees fight to death even though they are related?
Intense local competition
Queens in honey bee colony are sisters or half sisters
Only one bee can take over colony
Even though they are related they fight to death for the throne
Explain how indirect benefit occurs through discrimination
Kin discrimination so help relatives so indirect benefit to the actor because still passing on its genes (just through relatives)
What’s Kim discrimination
An individual identifies a relative and then cooperates with them
Difference between kin section and kin discrimination
Kin selection = process/modelling framework
Kin discrimination = behavioural action to identify relatives
Relationship between benefit form helping and kin discrimination
As benefit from helping increases
Kin discrimination increases
In groups where there are a lot of relatives there is less kin discrimination
Makes sense because if in group with list of relatives it means high probability who u interact with will be a relative anyway
When does kin discrimination pay most?
When I’m groups where you don’t know who are your relatives (can’t assume everyone is your relative)
How do individuals recognise their kin?
Environmental cues
Environmental cue example in ants
Take worker form one ant mount to another ant mound
Placed any will get savaged
Ants able to protect self and non self
Smell different (particular hydrocarbons on the outside)
How to bacteria detect kin and non kin?
Using toxin and immunity proteins.
Release toxin (kin will have immunity protein so can detect they are kin)
Incoming toxins = up regulate own toxins if feel being attacked. (So if they feel they r being harmed then they are aware there is the presence of another genotype - non kin)
Explain how indirect benefit occurs through green beard genes
X
Flocculation of yeast cells in beer
Stress response in high alcohol concentration yeast express protein causing aggregation then they rip out of solution and it protects them agains harm
Example of green beard discrimination in Flo proteins
Mix cells that make Flo protein and cells that do not make it
Cells that make it sticks together
(So flo protein trait allows for recognition - because aggregation is a result it allows cells to identify other cells with that specific loci)
- can also put two difference cell species in test tube both with flo proteins and the different species still aggregate because of the flo protein (demonstration of cooperation driven by a single locus (the locus for the Flo protein))
What complex of three effects do green beard genes require?
1) a perceptible trait
2) recognition of this trait in others
3) preferential treatment of those recognised
What do the frameworks explain?
why organisms evolve to expend their own resources to help others when it doesn’t seem to directly benefit them
Why does the inclusive fitness theory say organisms evolved to be altruistic ?
Because I’m being altruistic they gain indirect benefits and fitness because their genes are still passed on (it’s just through relatives)
Why does the multi level group theory say altruism evolved?
altruism evolved because if organisms are as a group it’s beneficial to everyone and worth the cost of having to spend some individual energy towards helping other son the group
(This is group mediated fitness)
