Rucete ✏ Campbell Biology In a Nutshell
Unit 7 ANIMAL FORM AND FUNCTION — Concept 51.4 Genetic Analyses and the Concept of Inclusive Fitness Provide a Basis for Studying the Evolution of Behavior
Animal behaviors evolve not only through individual reproductive success but also through aiding the survival of relatives. Genes influencing social behaviors can spread if they enhance the overall genetic contribution of individuals to the next generation—including via relatives.
1. Genetic Control of Behavior
- Some behaviors are linked to specific genes
- Example: fruit fly courtship controlled by the fru gene
- Normal males perform rituals; mutants do not
- Females expressing male fru gene show male-like behavior
- fru coordinates expression of multiple behavior-related genes
2. Genetic Variation Within a Species
- Behavior varies between populations due to natural selection
- Example: Western garter snakes
- Coastal snakes prefer banana slugs; inland snakes avoid them
- Lab-raised offspring retain preferences → genetic basis confirmed
3. Genetic Basis of Migratory Behavior
- Blackcap warblers traditionally migrated southwest to Africa
- Some populations now winter in Britain
- Lab studies confirm westward migration is inherited
- Likely evolved due to bird feeders and milder winters in Britain
4. Altruism and the Puzzle of Selflessness
- Altruism: reduces personal fitness but helps others
- Examples:
- Belding’s ground squirrels call out to warn kin, attracting predators
- Worker honeybees die defending the hive
- Naked mole rats: one queen; others serve colony roles
5. Inclusive Fitness and Kin Selection
- Helping relatives can promote one's own genetic success
- Inclusive fitness = direct reproduction + indirect help via relatives
- Hamilton’s Rule: altruism favored if rB > C, where:
- r = relatedness
- B = benefit to recipient
- C = cost to altruist
- Example: saving a sibling may be favored if benefit outweighs cost
6. Kin Selection in Nature
- Belding’s squirrels: females (near kin) give alarm calls
- Worker bees: aid the queen (their mother)
- Naked mole rats: colony altruism benefits shared genes
7. Reciprocal Altruism
- Altruism between non-relatives possible if favors are returned
- Requires:
- Stable social groups
- Repeated interactions
- Punishment of cheaters
- Examples:
- Vampire bats share blood meals
- Primates groom socially
- Humans: cooperation often follows tit-for-tat
8. Human Behavior and Sociobiology
- Human behavior shaped by culture, not just evolution
- Play may aid adaptation to unpredictability
- Sociobiology: links social behavior with evolutionary theory (E.O. Wilson)
- Controversial due to application to human society
- Cultural norms, laws, and ethics can override genetic advantage
In a Nutshell
Behavior evolves through both direct genetic influence and evolutionary benefit to relatives. Genes like fru or vasopressin receptors can control complex behaviors, while kin selection and inclusive fitness explain altruism. Even in non-relatives, reciprocal cooperation can emerge under stable social conditions. Human behavior reflects both biology and culture, blending evolutionary roots with societal development.