population pressure
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Families lived together in traditional China and sons remained on the land; division of family land led to tiny plots and rural poverty. Because labor was so cheap, the country did not urbanize or mechanize. The Communist government started out with a pro-natal stance, but after experiencing the famine of the Great Leap Forward, moved strongly to fertility control. Fertility declined rapidly in the 1970s, but to counter momentum, the One-C...more
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Mutations are the origin of genetic diversity. Mutations introduce new traits, while selection eliminates most of the reproductively unsuccessful traits. Sexual recombination of alleles can also account for much of the genetic diversity in sexual species. In some instances, population size can affect diversity and rates of evolution and fixation, but in other cases population size does not matter.
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Figuring out the partial pressures of various gases in a container.
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Introduction to Evolution, Variation in a Population and Natural Selection
Khan Academy / Philosophy
Introduction to evolution, variation in a population and natural selection.
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1) Population in China: Until recently, Chinese families did not much alter their fertility depending on life events such as deaths of children. However, under government prodding and eventually coercion, fertility dropped drastically in China in the 1970s, but to counteract momentum, the One-Child Policy started in 1979-80. 2) Population Growth and Economic Development: In Asia, rapid fertility drops have preceded economic booms by approx...more
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Concerns about low fertility have been present in many countries for at least 100 years. A large population was considered essential to national power. But the issue is never simply a shortage of warm bodies: overall the world population has increased dramatically over this period and untold numbers would immigrate, if allowed. The issue is the number of the 'right sort' of people, defined as those having preferred national, religious, rac...more
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Hypothesis Test Comparing Population Proportions.
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Prior to Malthus, population growth was seen as good for the power and wealth of a country. The rapid population growth of America was crucial in expelling England (via the Revolution) and France (via the Louisiana Purchase) from the US. But in fact, the numbers of the poor were growing in Europe in the 1700s. Malthus argued that poverty was due to an imbalance between people and resources; since population could rise very fast, it could a...more
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Census data is often politically influenced and hence inaccurate. The birthrate in developing countries is nearly twice that in developed countries. Most humans live in less developed countries, so the world birthrate is near the higher number. The world birthrate is two and a half times the death rate; we are not close to population stabilization. Almost everywhere, the death rate has been drastically reduced; further changes will not mas...more
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The ideal-gas law is introduced, and the rate of momentum transfer from the gas molecules to the vessel walls is related to pressure. The concepts of phase diagrams and phase transitions are also introduced, and they are explored with fire extinguishers, boiling water, and cooled balloons filled with air. The ideal-gas law holds (approximately) when you have only gas; it doesn't hold whenever there is any liquid present. Professor Lewin us...more
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Until recently, the world population has been growing faster than exponentially. Although the growth rate has slowed somewhat, there are about 80 million more people each year and about 3 billion more will be added by 2050 (a 50% increase). Population will probably increase more beyond that. Such growth is unprecedented and we cannot predict its long-term effects. The environmental impact of this population increase is bound to be astronom...more
