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Lecture 4

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University of Toronto St. George
Ronniede Sousa

The economic view of biology - The economic point of view consists in evaluating an action in terms of the value of its consequences – utilitarianism - You have to determine which consequences might occur and then think about how likely each event is to occur - Bayesian decision theory = the expected utility u of an opinion is the sum of the values of each possible outcome d weighted by its probability p Key tenets of modern evolutionary biology - All living things have a common ancestor - Diversification is largely random - Natural selection shapes adaptation - The mechanism of heredity is mostly genetic - Phenotypes are selected, but what are inherited are features of genotypes - Phenotype = apparent type, ex. brown eyes, blonde hair The logic of evolution by natural selection - A source of variation of diversity - Heritability, which is almost but not quite perfect, so that genetic mutations aren’t constantly happening – but change relies on there being genetic mutations - A differential rate of success in survival - This pattern applies equally to learning and to evolution, as well as to cultural transmission and the process of technology - Variation = variety of forms and limited living space - Differential success = some are more viable - Heritability = traits are passed on - Natural selection leads to genetic variability, which leads to the elimination of the less fit - Operant conditioning reinforces memory and skill - Memetics produce cultural entities and transmit cultural information - If meme is easy to remember, it will survive The economic paradox - The reason economists don’t get much right is because their theory applies well to evolution but not very well to human behavior - In economics you have to assume that agents are rationally self-interested, but people are irrational - In biology, both interest and probability have objective measures, ie how probable it is that a given gene will be passed on and how many copies of itself a gene will leave in the long(ish) run - The idea that organs are perfect because they have evolved doesn’t logically follow - That’s because a lot of organs don’t actually work perfectly, ex. The eye What is sex? - At the most primitive level (bacteria), gene exchange exists without reproduction - One hypothesis is that gene exchange allows repair - But in multicellular organisms, there are a number of different things that take place - Division of labour – cells are differentiated so specialized cells take care of replication - Gametes contain half an individual’s genes - Two gametes fuse for a full complement of genes - Meiosis – the cells duplicate and then divide twice Drawbacks of sexual reproduction - The cost of meiosis is that for any given gene, the chances of being transmitted is only 50% - Sexual reproduction isn’t really even reproduction because it takes two and makes one instead of taking one and making two - Finding an appropriate mate is complicated - Twof
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