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Biology 3300- Social Behaviour

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University of Lethbridge
BIOL 3300
Theresa Burg

Biology 3th0 Mar.10 Chapter 12- Social Behavior Examples of Social Behavior: Reciprocal Altruism - Vampire bats (Feb.10 lecture) o Donor has a high cost o Recipient will benefit from the donor o Donor that gave up 5% of body weight is then picked up by the recipient  The donor gives up weight and becomes 6hrs closer to starvation  The recipient picks up this weight and becomes 16hrs farther from starvation - Reciprocal altruism: altruism between non-kin - For selection to result in reciprocal altruism: o Cost to donor ≤ benefit to recipient o Recipients that don’t reciprocate are punished (no cheating is allowed) - Likely to evolve when: o Stable groups o Multiple opportunities o Individual remembers donor’s behavior o Altruism is bidirectional  One can’t always be the donor and one can’t always be the recipient Eusociality - Extreme form of reciprocal altruism - Social system with: o Co-operative care of young o Reproductive division of labor o Over-lapping generations  Need it so the behavior can be taught to the next generation - Common in insects, also found in snapping shrimp and naked mole rats - Hamilton proposed haplodiploid systems are predisposed to eusociality o Haplodiploid  some are diploid, some are haploid - Hymenoptera (bees, wasps, ants) o Sterile female workers (2n) o Males (n) from unfertilized eggs  100% of male DNA comes from the mother - If single father, r within generation are going to be higher than between a mother- daughter - Haplodiploid system (bottom diagram) o Mom is diploid o Father is haploid; his allele automatically passed on to daughter o Relatedness from female to sister  (1/2 * ½) + (1/2 * 1) = 0.75  (1/2 * ½) is from the mother  (1/2 * 1) is from the father  1 represents 100% of the dad’s genome is the same as the sister o Female to brother  from mother (1/2*1/2) = ¼, doesn’t receive allele from father so there is no second half of the equation as seen in the female to sister - Females in haplodiploid systems benefit more through inclusive fitness, rather than reproduction - Haplodiploidy hypothesis o Females increase fitness by helping queen produce sisters o Relatedness to sister (0.75) is higher than to brother (0.25), predict a 3:1 (female to male) ratio BUT queen invests equally to produce sons and daughters  It doesn’t matter to the Queen if she has more sons or daughters; she invests equally in her offspring o Who wins? Queen or worker?  Depends on the organism and the situation Ex: Termites caste system is regulated by pheromones produced by king and queen - King and Queen will produce sex specific pheromones; Queen pheromones influence females while the King’s pheromones influence males - Worker will turn into sterile soldier when pheromone levels are high - Worker will turn into king or queen when pheromone levels are low - Really large colonies may be able to support numerous kings and queens; smaller colonies won’t be able to support a number of kings and queens - A death in the royal family or an increase in the size of the colony results in a decrease in pheromone concentration - Sex specific pheromones can regulate the amount of soldiers present - Inhibit workers of the same sex from molting into reproductive adults Wood ant offspring ratio - Queen produces eggs ~1:1 - Appears that workers are able to discriminate their level of care and have fewer male eggs hatch and have more females hatch and grow up - There is a female bias present at hatching What about eusociality? - Haplodiploid is important, but is it the reason why so many hymenoptera are eusocial? 1) Predict that the wo
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