# Chapter 7 - Chapter 7(7-1 The human population curve looks...

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Unformatted text preview: Chapter 7 (7-1) The human population curve looks logistic Why has the human population increased so rapidly? a) Expanded brain = exploit many new habitats b) Agriculture = higher population density c) Avoided limits to growth with technology (medicine, fossil fuels, sanitation) Population Change Equation = (births + immigration) – (deaths + emigration_ Crude birth rate and crude death rate- CBR is the number of live births per 1,000 people in a population in a given year. CDR is the number of deaths per 1,000 people in a population in a given year. Percent population change = (birth rate/1000 – death rate/1000) * 100% Doubling rate (rule of 70)- the time it takes for a population growing at a specified rate to double its size. A quick way to calculate is 70/percentage growth rate = doubling time in years Fertility rates: replacement (2.1) and total- Replacement is the number of children a couple must bear to replace themselves (2.1 is developed countries and 2.5 in developing). Total is the average number of children a woman typically has during her reproductive years (2.7 globally in 2005). US fertility rates- TFR reached 3.7 children per woman in 1957; since then it has declined remaining at or below replacement level since 1972. Why have fertility rates dropped in the US?- Woman have become more a part of society but having jobs and becoming equal to men. Factors affecting birth and fertility rates : Child labor, Cost of raising a child, Pensions, Urbanization, Employment and education of women, Age at marriage, Reliable birth control, Culture Factors affecting death rates- increased food supplies, better nutrition, advances in medicine, improved sanitation and personal hygiene, safer water supplies.improved sanitation and personal hygiene, safer water supplies....
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Chapter 7 - Chapter 7(7-1 The human population curve looks...

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