L10 inclusive fitness theory Flashcards
What is inclusive fitness?
A measure combining direct fitness (personal reproduction) and indirect fitness (gains from helping kin reproduce), reflecting total genetic propagation.
Why is inclusive fitness considered a cornerstone of evolutionary biology?
Because it explains social behaviors like cooperation and altruism by accounting for genetic gains through both self and relatives.
What contextual understanding of inclusive fitness would you have gained in earlier MBiol courses?
That it extends Darwinian fitness by including indirect genetic contributions via kin selection, illustrated in social insects or birds.
Why does understanding foundational inclusive fitness concepts matter for advanced MBiol discussions?
It sets the stage for exploring controversies, new theoretical developments, and special genetic systems that refine the standard view.
What does Hamilton’s rule state?
An altruistic behavior can evolve if r × B > C, where B is the benefit to the recipient, C is the cost to the actor, and r is their genetic relatedness.
How is Hamilton’s rule different from inclusive fitness?
Hamilton’s rule is the inequality rB > C predicting when altruism is favored, whereas inclusive fitness sums all genetic gains (direct + indirect).
What is group selection?
The idea that natural selection can act on groups, favoring traits that benefit group survival even if costly to individuals.
How does group selection relate to inclusive fitness?
Debates focus on whether group‐level outcomes simply recapitulate kin selection predictions or represent a distinct conceptual framing despite mathematical equivalence under some conditions.
How is the benefit (b) in Hamilton’s rule defined?
The increase in the recipient’s reproductive success attributable to the actor’s help.
How is the cost (c) in Hamilton’s rule defined?
The decrease in the actor’s own reproductive success due to performing the altruistic act.
What challenges arise when measuring b and c in real biological contexts?
It’s hard to isolate additional offspring caused by a specific act, and assuming additive effects fails when benefits multiply over repeated help.
What does Charlesworth’s counterexample illustrate about Hamilton’s rule?
That under strong selection or frequency‐dependent scenarios, genes for suicidal altruism may not spread even if rB > C appears satisfied, showing key assumptions (weak selection, action independence) can break down.
What is the geometric view of relatedness?
It uses a 0–1 line of genotype frequency to show how an actor’s genotype correlates with a recipient’s relative to the population mean; relatedness is the slope of that regression.
What are typical relatedness coefficients in diploid organisms for full siblings, half-siblings, and cousins?
Full siblings r = 0.5, half-siblings r = 0.25, cousins r = 0.125.
How do pedigree analyses empirically support these diploid relatedness values?
Genetic marker studies in lab mice, humans, and captive breeding consistently confirm the expected coefficients via parent-offspring allele tracking.
What defines a haplodiploid genetic system and which taxa exhibit it?
Males develop from unfertilized (haploid) eggs and females from fertilized (diploid) eggs; seen in bees, ants, and wasps.
Why do haplodiploid sisters share about 75% of their genes?
A haploid male transmits his entire genome to daughters (100%), while the diploid mother transmits only half (50%), so sisters average r ≈ 0.75.
How do regression and life-for-life relatedness calculations differ in haplodiploids?
Regression uses pure probability of shared genes; life-for-life incorporates reproductive value differences, yielding slightly different numerical r’s.
What empirical evidence confirms high sister–sister relatedness in haplodiploid species?
Genetic-marker surveys in honeybee and ant colonies show ~0.75 relatedness, matching observed worker altruism like brood care and defense.
What is the weak selection assumption in inclusive fitness theory?
That fitness effects of social behaviors are small and additive, so gene interactions remain linear; strong selection can break this.
What does the additivity assumption of benefits and costs state?
That each altruistic act’s payoff sums linearly with no synergy or diminishing returns.
Give a counterexample to benefit/cost additivity.
In some microbes or insects, repeated cooperative acts multiply survival (exponential gains), invalidating simple summation of b and c.
Why is random mating assumed under inclusive fitness models?
It ensures well-mixed populations so average relatedness measures are meaningful; spatial or non-random structure can skew r.
What empirical patterns support the effectiveness of inclusive fitness theory?
Studies in ground squirrels, birds, and social insects show altruistic behaviors aligning with kinship predictions.
