Population Pressure
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We apply the idea of evolutionary stability to consider the evolution of social conventions. Then we consider games that involve aggressive (Hawk) and passive (Dove) strategies, finding that sometimes, evolutionary populations are mixed. We discuss how such games can help us to predict how behavior might vary across settings. Finally, we consider a game in which there is no evolutionary stable population and discuss an example from nature.
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In this lecture, we use the overlapping generations model from the previous class to see, mathematically, how demographic changes can influence interest rates and asset prices. We evaluate Tobin's statement that a perpetually growing population could solve the Social Security problem, and resolve, in a surprising way, a classical argument about the link between birth rates and the level of the stock market. Lastly, we finish by laying...more
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Geography is very important in ecology. Two major systems have been designed to model this, island biogeography and metapopulations. The idea of metapopulations is more recent, and has emerged as the dominant theory. Metapopulations are populations in multiple neighboring areas. The population of a species in any individual area may go extinct, but the metapopulation still survives. The theory of metapopulations has gained momentum in...more
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In the second of his two lectures in honor of Arthur Okun, Professor Summers points out that real interest rates have been very low in the current subprime crisis. This indicates that the shock to the economy was more a financial breakdown shock than a disinflation shock. But financial breakdown shocks are not necessarily very harmful to the economy, so long as financial intermediation capital is not destroyed. In a financial crisis like...more
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In East and South Asia there are many more boys than girls. Previously, this resulted from female infanticide, now it is sex-selective abortion. In those cultures, girls generally marry out of the family as teenagers and thus provide no benefit for the family that raised them. Bangla Desh is agriculturally very rich, but its population is so dense that per capita income is one of the lowest in Asia. Despite the poverty, an excellent...more
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The economic concept of game theory can be readily applied to evolution and behavior. By analyzing encounters between organisms as a mathematical "game," important information such as fitness payoffs and the proportions of "strategies" played by each group within a population can be inferred. While oftentimes these games are too simplified to apply directly to actual examples in nature, they are still useful models that help convey...more
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Reaction norms depict the range of phenotypes a single genotype can produce, depending on the environment. Reaction norms must fit within an organism's phylogenetic constraints. They can differ for different individuals within a population, but some traits differ very little based on the environment; some do not differ at all.
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Originally, altruism and self-sacrifice were thought to be incompatible with natural selection, even by Darwin. Now we have several explanations for how altruism can increase an individual's fitness. One is kin selection, or the idea that helping relatives can help increase one's genes in the population. Another involves ecological constraints and punishments. Here, individuals contribute to the group and wait their turn to reproduce.
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Systems consisting of pendulums and springs can freely oscillate at their natural frequencies (also called normal modes). When we expose a system to a wide spectrum of frequencies, the response will be very large at the normal mode frequencies (resonances) of that system. Examples include musical instruments (standing waves on violin strings and pressure waves in wind instruments), and torsional standing waves on a bridge driven by strong winds.
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Earl discusses the importance of understanding and developing games for local markets. EA started a studio in Shanghai to learn about China's gaming population. He also talks about protecting EA's IP via an online distribution mechanism.
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This lecture covers resistive forces such as air drag. It includes the viscous (linear in velocity) and pressure (quadratic in velocity) terms. Quantitative demonstrations with balloons and with ball bearings dropped in syrup are shown. He concludes with numerical calculations of air drag examples, also discussing the contribution of air drag to the quantitative experiments down earlier in the course with falling apples.
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Understanding allele and genotype frequency in population in Hardy-Weinberg Equilibrium.
