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Section OneBrief words of wisdom for doing well in Bio 150:Know when you don’t know, and when you don’t know, get help! (on Piazza)Translation: You should always be evaluating your knowledge of the material. It’s important to expose weaknesses in understanding before taking the exam. Some effective ...

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Section One Brief words of wisdom for doing well in Bio 150: Know when you don’t know, and when you don’t know, get help! (on Piazza) Translation: You should always be evaluating your knowledge of the material. It’s important to expose weaknesses in understanding before taking the exam. Some effective ways to test your knowledge (in my suggested order of approach): ● The extended notes are an invaluable resource. Rely on them heavily! ● After you’ve attended lecture and read the extended readings, tackle the weekly reading assignments. Focus on major take home points and the experimental methods used to reach these conclusions. Make sure to connect the papers to the topics or examples from lecture. ● Attend section and come with questions ● Review section handout answers at home ● Use Piazza when you have questions (your fellow students are a key resource, and you can submit anonymously!) ● Go to office hours (see any of the TAs) Things that you really need to know: ● Basic tenets of Darwinian evolution ● The three building blocks of sociobiology ● Understanding kin selection on a mathematical level, to a certain extent. ● The application of game theory to reciprocal altruism. ● The problem of how reciprocal altruism starts. ● How to explain a number of realms of behavior with sociobiological principles. ● An array of critiques of the field. Our overall goal is to understand how a sociobiologist would make sense of animal behavior. This review: 1. Overview 2. Relatedness 3. Cooperation 4. Pair bonding/tournament species

Exercise 1: Overview

What are some pros and cons of categorical thinking? 1. Helps you remember and recognize an example of a group. 2. You tend to see members of a group as more similar than they actually are and members of different groups as more different than they actually are (color perception example). 3. Myopic focus on individual categories (buckets) by leading thinkers of the past has led to disastrous outcomes 4. outcomes Evolution (change over time) caused by a number of things. We focus on the big one: natural selection. What three conditions must be met in order for natural selection to proceed? 1. Heritability (DNA) 2. Variability (mutation) 3. Differential fitness (success in leaving progeny) Then what happens? Versions that confer more fitness will become more prevalent over time Sociobiology is the study of the evolution of behavior. What are the three core explanatory pieces you should be able to apply to a wide range of behavior? 1. Individual selection. "A chicken is an egg's way of making another egg." -Samuel Butler 2. Kin selection/inclusive fitness. "I will lay down my life for 2 brothers or 8 cousins" -JBS Haldane 3. Reciprocal altruism /inclusive fitness. "I will lay down my life for 2 brothers or 8 cousins" -JBaltruism. Five pieces of evidence for evolution? 1. Observable over past 100 years in short-lived species like staph bacteria & penicillin resistance 2. Fossil record shows tons of intermediate forms 3. Genetic evidence: we share huge percentages of our genomes with our closest evolutionary ancestors, and less the further you go back in time to most recent common ancestor 4. Geographic distribution of species: relatives are bunched together in space 5. Unintelligent design: vestigal structures like leg bones in dolphins, pyramidal system for finger movement Exercise 2: Relatedness Your buddy says, “I read that humans share 98% of their genes with apes, yet I read that I share 50% of my genes with my brother. How is that possible?” Teach your buddy some science. 50% of your alleles are shared with your brother. You and your brother have roughly ~100% of the same genes. You and an ape have approximately 98% of the same genes that likely contain different alleles.

Calculating degrees of relatedness: Show your calculations for... ● First cousins: 12.5%

● Half brothers: 25%

● Parent / child: 50%

Exercise 3: Cooperation Kin selection/inclusive fitness: Cooperate with relatives, encourage their reproduction. Reciprocal altruism: formalized through game theory with the prisoner's dilemma, represented in the schematic below:

What is Axelrod's famous winning strategy? What does even better under some conditions? ● Tit for tat. Will lose battles but win wars. Will lose to cheaters, but pairs of TfT will win more than cheaters ever will. ● Better with forgiving tit for tat (less prone to signal errors) ● Pavlov can exploit forgiving tit for tat What typically characterizes species that demonstrate reciprocal altruism? "Species that are social, long-lived enough and in sufficiently stable groups so that individuals interact with each other more than once (how else can the reciprocity occur?), smart enough to recognize individuals and, critically, smart enough to try to cheat at the reciprocity when it’s possible to get away with it (i.e., to not reciprocate an altruistic act), and smart enough to spot someone trying to cheat against them." forgiving tit for tat What are five examples of TfT or interesting elaborations? 1. Vampire bats (TfT) 2. Stickleback fish (TfT) 3. Gender switching fish who defect if the other defected (TfT) 4. Cowardly lions who are good hunters (different domains of contribution) 5. Huge naked mole rats plugging up holes (different domains of contribution) 6. naked mole rats plugging up holes (different domains of contribution) What is the Greenbeard effect? Not about recognizing kin, necessarily, but instead just one gene that allows for recognition of the gene in other individuals, and cooperation with other individuals that have that gene What is rock-paper-scissors equilibrium? Is this true cooperation? Can we see it Actually restraint from competition. Not true altruism. An example of this process is found in Kerr, et al., where we see 3 populations of E. coli maintain their diversity on localized scales because: ● C makes a toxin that kills S ● S outcompetes R because it grows faster (it has a pump that takes up nutrients/toxin) ● R outcompetes C (they grow faster b/c they lack the metabolic cost of making toxin) How does cooperation/altruism start?

Founder population cooperates on a basis of kin selection. Then when re-integrated into large population, they keep "winning the war" and cooperation crystallizes outward or noncooperation is driven extinct. Exercise 4: Pair bonding/tournament species In class, we saw that natural selection and sexual selection can apply different (sometimes opposing) forces. How do they apply to individual selection? 1. Natural: adaptedness to surviving in the environment 2. Sexual: adaptedness at attracting a mate How do they apply to kin selection (inclusive fitness)? 1. Natural: Engage in behaviors that allow related individuals to survive and reproduce 2. Sexual: Work to make related individuals seem attractive to potential mates How do they apply to cooperation/altruism? 1. Natural: non-related hunters cooperating to get game they couldn't get alone. 2. Sexual: cooperatively making a non-relative more attractive to mates

How do we explain competitive infanticide? 1. Definitely not for the good of the species! 2. When the average tenure of the head male is shorter than the average interbirth interval in females. 3. Males operating under individual selection: wipe out other infants so mothers can be impregnated (tie to oxytocin - nursing - fertility suppression - endocrinology foreshadowing), plus less competition for his future offspring. 4. Females coping via individual selection principles: smell of new male causes spontaneous miscarriage because it doesn't make sense to have an offspring that will be killed. Save on pregnancy costs and get pregnant with the new male. Female still has 50% genetic interest in her offspring whether it's old male or new. 5. Females coping via kin selection: defending their children up to a point (when would they lay down their life?), also faking pseudo-estrus to fool the new head male into not forcing them to spontaneously miscarry from harassment.

What are some further behavioral examples explained well by sociobiology? 1. Kidnapping by male baboons (and not kidnapping when high-ranking male just joined the troupe) 2. Relatedness in dominance hierarchies. Females inherit their rank 3. How do sex ratios play out for pair bond vs. tournament species? ● Males are more "expensive" but high ranking tournament species females will gamble on a son instead of a daughter. What's the proximate mechanism here? Higher-ranking females have better nutrition so sons will be more likely to be carried to term.

● Sex ratios will stabilize over time near 50-50.ratios will stabilize over time near 50-50. 4. Paying attention to alarm calls as a function of relatedness 5. Male-male cooperation 6. Instances of polyandry (multiple males leading a harem). Usually adelphic (by related males). Includes humans (see traditional Tibetan marriage patterns). 7. Why would you mate with relatives? o Share more genes with them so more of your genes make it into the next generation. Great! o But if they're too closely related than recessive disease-causing alleles are likely to be inherited and cause disease. Not so great! o Where does the "optimal" mating occur, according to the Helgason "Kinship and Fertility" reading? 3rd or 4th cousin matings produce the most fertile offspring. together and often kill neighboring males. This is protowarfare and genocide....