Human Population Growth om/watch?v=4BbkQi QyaYc&feature=playe r_detailpage

Exponential growth Growth without limits. The last 200 years of human population growth has been exponential. World population will soon top 7 billion.

Three reasons for human exponential growth Developed ability to expand into new, diverse habitats. Emergence of modern agriculture allows more people to be fed per unit of land. Death rate drop due to sanitation systems, vaccine, and antibiotics.

Population increase # of births Amount of immigration.

Population decrease # of deaths. Amount of emigration.

Crude birth rate Live births per 1000 people in a population in one year.

Crude death rate Deaths per 1000 people in a year.

Zero population growth Crude birth rate equals crude death rate and migration is 0.

Who has the largest populations? China with 1.3 billion. India with 1.1 billion. U. S. with 304 million.

Annual rate of population change (Births+Immigration – Deaths+Emmigration) Rate at which the size of a population changes in %. World growth rate is 1.22% (82 million in 2008) per year. 0.1% in developed countries and 1.5% in developing countries. This adds more pressure to already crowded places.

Doubling Time Doubling time = 70 divided by % population change

Cultural Carrying Capacity Optimum population level that would allow most people to live in reasonable comfort and freedom without impairing the planet from sustaining future generations.

Fertility rates- types: Replacement level fertility- number of children a couple must have to replace themselves. Goes up in undeveloped countries because of higher infant mortality.

Total fertility rate- estimate of the average number of children a woman will have in her life. Has declined to 2.6 children per woman (1.6 in developed countries and 2.8 in developing). Not few enough to stabilize the world’s population.

Factors effecting birth and fertility rate Level of education. Level of affluence. Child labor practices. Working children higher in developing countries. Urbanization. People living in cities tend to have better access to family planning and have fewer children.

Cost of raising child. Much higher in developed countries. $290,000 to raise a middle class child to 18 years. Opportunities for women. TFR’s are lower when when have access to education and jobs as in developed countries. Infant mortality rates. Low IMR leads to fewer children because fewer die in the first year.

Age of marriage. Lower when women get married after 25. Pension system availability. Reduce the need to have many children to support parents in old age. Abortion and Birth control availability. More likely in developed countries.

Religious beliefs. Cultural norms. Traditions. These sometimes favor large families.

Factors affecting death rates Better nutrition. Increased food supply and distribution. Fewer infant deaths and longer life expectancy. Since 1955 life expectancy has increased from 48 to 68, 77 in developed countries and 67 in developing.

Medical and public health technology. Immunizations, antibiotics, improved sanitation and safer water supplies.

Useful Health Indicators Life expectancy- average # of years an infant is expected to live. U.S. rates behind 41 other developed countries at 78. Lack of universal health care and high obesity rate are blamed. Yet more is spent on health care in the U.S.

Infant mortality infant deaths out of 1000 before 1 year of age. Indicates nutrition level, health care and general quality of life to 2008 world IMR dropped from 20 to 6.3 in developed countries and 118 to 59 in developing countries.

Population age structure diagrams Used by demographers to analyze a countries population trends.

Plots the % of males and females of various ages in a population.