extra inclusive fitness year 2 Flashcards
What is social evolution?
Change in gene frequency in a population driven by natural selection, mutation, and drift, involving effects on others’ reproductive fitness.
What is reproductive (direct) fitness?
The effect of an individual’s actions on its own survival and fecundity—i.e., its success in passing genes to the next generation.
What is indirect fitness?
The benefit an individual gains by helping relatives share similar genes, measured via kin selection.
At what scales can social evolution occur?
From gene → genome → complex cell → multicellular organism → population → societies → inter/intra-specific interactions.
How are social behaviours classified according to Hamilton’s table?
By effects on actor vs. recipient fitness: mutual benefit (+/+), selfishness (+/−), altruism (−/+), spite (−/−).
What defines mutual benefit?
A behaviour that increases both the actor’s and the recipient’s fitness.
What defines selfishness?
A behaviour that increases the actor’s fitness but decreases the recipient’s fitness.
What defines altruism?
A behaviour that decreases the actor’s fitness while increasing the recipient’s fitness.
What defines spite?
A behaviour that decreases both the actor’s and the recipient’s fitness.
Why can cheating be a problem in social groups?
Selfish individuals may exploit group benefits without contributing, undermining cooperation.
How is cheating controlled in cooperative groups?
Through policing, enforcing, or sanctioning mechanisms that suppress selfish behaviour.
What early thinkers contributed to social evolution theory?
Linnaeus, Darwin, Mendel, Fisher, Wynne-Edwards.
What did Linnaeus propose about species interactions?
He claimed they were based on judgments of “right” and “wrong,” without observational support (now rejected).
What was Darwin’s contribution to social evolution?
He linked social traits to direct and indirect fitness and observed them in nature.
What mistake did Fisher make regarding indirect fitness?
He argued that indirect fitness (kin benefits) was unimportant.
What is kin selection?
The process by which traits are favoured because they benefit related individuals.
What is the coefficient of relatedness (r)?
The probability that two individuals share a given gene, calculated as the sum of (0.5)^L over all genealogical pathways.
How do you calculate r for parent–offspring?
There is one pathway of one generation: r = (0.5)^1 = 0.5.
How do you calculate r for full siblings?
Two pathways of two meioses each: r = (0.5)^2 + (0.5)^2 = 0.25 + 0.25 = 0.5.
What is inclusive fitness?
The sum of changes in an individual’s direct fitness plus its indirect fitness via relatives.
State Hamilton’s rule.
An altruistic act evolves when rB > C (where C is the cost to actor, B is the benefit to recipient, and r is relatedness).
What ecological factors influence kin selection?
Factors that determine the cost (C) and benefit (B) of behaviours in specific environments.
What is an example of altruistic alarm calling in ground squirrels?
Female ground squirrels emit alarm calls when spotting predators, risking exposure (cost) to warn nearby kin to escape.
Why do female ground squirrels give more alarm calls than males?
Because females live nearer their relatives, increasing their indirect fitness by protecting kin.
