10. Social Evolution Flashcards
Define eusociality
Extreme cooperation – e.g. ants, wasps, bees, termites – helpers are sterile for their entire life
What are the four classifications of behaviour?
Mutualism, selfishness, altruism, spite
What are the four ways cooperation can evolve?
Kin selection, By-product benefits, Reciprocity, Enforcement
Why do parent s invest in offspring?
Because they carry some of the parent’s genes
What is the coefficient of relatedness?
The probability that an allele in one individual will be identical by decent as that in another individual
What is the coefficient of relatedness between parents and offspring?
0.5 or 50%
What does relatedness refer to?
The probability of sharing a copy of a gene identical by descent
How does kin selection ‘work’?
By increasing success of copies of a gene, relative to other copies of that gene (ie relative to population mean)
What is Hamilton’s rule?
rB-C > 0
r = relatedness, B = direct benefit to recipient, C = cost to actor
Hamilton suggested two mechanisms whereby altruism towards kin may be favoured by natural selection…
1) Kin discrimination - individuals recognise and direct care towards kin
2) Limited dispersal - population viscosity ensures that interactions occur between genetic relatives
how can we be sure kin selection is occurring and not just due to proximity or environmental cues?
Russell & Hatchwell 2001 - long tailed tit nest failed, were given a choice of helping kin or non kin, chose kin
How does limited dispersal lead to increased relatedness?
Ensures interactions occur between genetic relatives
Leads to competition between relatives for mates food resources etc - does not necessarily favour altruism
What is one suggestion for why spite may seem to occur?
If it leads to a benefit for a third party
What prevents selfishness eroding the group from within?
Wynne-Edwards 1962 suggests behaviours are adaptations for the group not individuals, populations have self regulatory mechanisms - problem is individuals are the unit of selection
How are bodies a cooperative association of cells?
The somatic cells work and do not reproduce, so that the gametes can reproduce. When this cooperation breaks down and the body cells start reproducing = cancer
