World Population Growth.docx

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Biological Sciences Program
BSCI 106
Alexandra Bely

World Population Growth  Human population size has been well below 1 billion until recently, exponential growth! (figure 53.22)  Thomas Malthus pointed out growth potential, influenced Darwin’s struggle for existence theory, believed food production couldn’t keep pace, predicted poverty/famine/disease/etc.  If you have exponential growth, you need more resources, if your resources can’t keep up, period of poverty/famine/disease will follow, leading to major reduction and leveling out/stabilization (doesn’t always have to happen this way)  How did we get here? Technology, curing and preventing diseases, industrial and scientific revolutions, sanitation (waterway systems, access to clean water)  Stages of Human Population Growth: o 12,000 years ago: hunting, gathering, mostly nomadic- FOLLOWED resources, ~5 mil humans, population limited by high infant mortality and short lifespan, mostly low impact on environment o 1-8000 years ago (1650 AD): agriculture becomes widespread, settled lifestyle (living close to resources, settling locally) promotes more stable food supply and greater food storage (fewer famines), humans manage resources and local environment, birth rate increase and death rate decrease o 1650-present: major technical/scientific advances (hygiene, med, food production), birth rate goes way up and death way down, huge increase in population density (exponential growth), major effects on human condition and ENVIRONMENT  doubling time dramatically shortened in our exponential growth (1500 years)  first billion took 2,000 years, time required to add a billion dramatically shortened  current world population: ~7 billion  current avg. doubling time: ~50 years  recent avg. time to add billion people: ~10 years  projected to reach 10 billion: ~2060  large net increase (77 mil added per year)  enormous pop size has major consequences: habitat loss, global environmental change, depletion of living resources, species extinction, decreased living standards, political instability, acute shortages in basic resources  good news: fertility rates declining and r (per capita growth rate) is  however, r is still very high and population will keep increasing because of “population momentum” due to large number of females ALREADY BORN (fig. 53.24)  industrialization can improve living conditions and decrese b and d BUT typically, de
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