Biological Altruism: Fitness, Kin Selection, and Social Exchange

All flashcards

Biological altruism

Behaviour that increases another individual's reproductive fitness while decreasing the actor's own direct fitness; it is defined by consequences, not intentions.

Inclusive fitness

An individual's direct reproductive success combined with effects on relatives' reproductive success, weighted by genetic relatedness.

Hamilton's rule

A costly act can be favoured by kin selection when the relatedness-weighted benefit exceeds the cost: $rB > C$.

Reciprocal altruism

Helping an unrelated individual when help may be returned later, making the exchange beneficial over time.

Obligate and facultative altruism

Obligate altruism involves a lasting direct-fitness loss; facultative altruism involves a temporary loss that may be followed by personal reproduction.

Quiz questions

1. In Hamilton's rule, when can a costly act be favoured by kin selection?Answer: When the recipient's benefit weighted by relatedness exceeds the actor's cost.
2. How does tit-for-tat behave in later rounds of a repeated Prisoner's Dilemma?Answer: It copies the partner's previous move.
3. Why can simple appeals to the good of a group fail to explain cooperation?Answer: Individuals that benefit without contributing may gain a reproductive advantage.
4. What does the handicap principle propose about costly signals?Answer: Their cost can make them reliable because individuals in poor condition may not afford them.
5. What is autothysis in some social insects?Answer: A defensive act in which an individual fatally ruptures a specialized gland.