HUMAN SOCIETY

FACTORS AFFECT POPULATION Limiting factor limits the growth, abundance or distribution of the population of a group Limiting factor principle

POPULATION GROWTH Environmental resistance – all factors that work together to limit the growth of a population Carry capacity – the maximum population of a given species that a habitat can sustain indefinitely Exponential growth – starts slow then accelerates; yields a j-shaped curve when plotted Logistic growth – growth decreases as it meets resistance then stabilizes; yields a s shaped curve

POPULATION GROWTH Exponential growth can overshoot carry capacity and experience a sharp decline or population crash (dieback)

ENVIRONMENTAL DENSITY DEPENDENT POPULATION CONTROLS Parasitism Infectious disease Competition for resources These regulate population

ENVIRONMENTAL DENSITY INDEPENDENT CONTROLS Severe freeze Hurricane Fire Habitat destruction

HUMAN POPULATION GROWTH CONTINUES BUT IT IS UNEVENLY DISTRIBUTED Reasons for human population increase Movement into new habitats and climate zones Early and modern agriculture methods Control of infectious diseases through Sanitation systems Antibiotics Vaccines Health care Most population growth over last 100 years due to drop in death rates

POPULATION GROWTH Governed by births, deaths, immigration, emigration Population increases by births and immigration Population decreases by deaths and emigration Pop. = (births + immigration)-(deaths + emigration)

Population growth in developing countries is increasing 9 times faster than developed countries % of growth in developing countries billion people

FIVE MOST POPULOUS COUNTRIES, 2010 AND 2050 Fig. 6-4, p. 127

AGE STRUCTURE Distribution of individuals among age groups Impacts speed of population increase or decrease Age groups: pre-reproductive, reproductive, post-reproductive

Fig. 6-12, p. 136 MaleFemaleMaleFemaleMaleFemaleMaleFemale Expanding Rapidly Guatemala Nigeria Saudi Arabia Expanding Slowly United States Australia China Stable Japan Italy Greece Declining Germany Bulgaria Russia Prereproductive ages 0–14 Reproductive ages 15–44 Postreproductive ages 45–85+

AS COUNTRIES DEVELOP, THEIR POPULATIONS TEND TO GROW MORE SLOWLY Demographic transition First death rates decline Then birth rates decline Four stages 1. Preindustrial 2. Transitional 3. Industrial 4. Postindustrial

Fig. 6-17, p. 140 Stage 1 Preindustrial Stage 2 Transitional Stage 3 Industrial Stage 4 Postindustrial Population grows very slowly because of a high birth rate (to compensate for high infant mortality) and a high death rate Population grows rapidly because birth rates are high and death rates drop because of improved food production and health Population growth slows as both birth and death rates drop because of improved Population growth levels off and then declines as birth rates equal and then fall below death rates Total population 50 Birth rate Death rate Birth rate and death rate (number per 1,000 per year) 10 0 LowIncreasingVery highDecreasingLowZeroNegative Growth rate over time food production, health, and education

Fig. 6-15, p. 138 Some Problems with Rapid Population Decline Can threaten economic growth Labor shortages Less government revenues with fewer workers Less entrepreneurship and new business formation Less likelihood for new technology development Increasing public deficits to fund higher pension and health-care costs Pensions may be cut and retirement age increased