sept 9

sept 9 - crude birth rate The number of childbirths per...

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Humans and Natural Resources One constant that has accompanied the development of conservation as a science and social movement has been the steady increase in human population size. Modern Homo sapiens – 200,000 years World population growth. 1804-1827 (123 years) 1 billion people added 1927-1960 (33 years) 2 billion people added 1960-1975 (15 years) 3 billion people added etc… Population Growth Populations grow and shrink based on the relative magnitude of four processes; birth, death, immigration, and emigration One way to look at birth rates is the total fertility rate (TFR), the number of theoretical births per woman during her lifetime, calculated by summing age-specific reproductive rates from 15-45 (49) Not dependent on population age structure. Replacement TFR is about 2.1 (industrialized), 2.5-3.3 (developing) Another measure of the magnitude of birth is the
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Unformatted text preview: crude birth rate The number of childbirths per 1,000 people per year. Affected by the age structure of the population. The crude death rate is the number of deaths per 1,000 people per year Also dependent on age structure and probability of morality, may even be higher in developed than developing countries as populations age. Doubling time = 70/annual percentage growth rate Population Age Structure In addition to how many people there are, another important facto influencing population growth is the age structure – the population pyramid Population Change Countries generally move from expansive to constrictive age structures as they become industrialized and develop their countries. The demographic transition When death rates start to fall, get birth rates up....
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