TWO TYPES OF POPULATION GROWTH IN ECOSYSTEMS: EXPONENTIAL GROWTH LOGISTICAL GROWTH Which represents the human population??
Malthusian Growth (Irruptive Growth) - Population explosions followed by population crashes. Malthus concluded human populations tend to grow until they exhaust their resources and then crash. POPULATION CHANGE: N = (birth + immigration) – (death + emigration) When these factors balance out it is known as ZERO POPULATION GROWTH (ZPG)
I heart musti Population Growth 1. Ability to expand into diverse habitats and climates 2.Agriculuture 3. sanitations systems, antibiotics, vaccines
FACTORS AFFECTING HUMAN POPULATION SIZE Crude Birth Rate = # of live births per 1000 Crude Death Rate = # of deaths per 1000 95% of daily population growth occurs in developing countries Global Growth Rate = 1.3% (equivalent to adding another USA every 3.6 years) China = 1.5 billion India = over 1 billion USA = ~300 million ~40% 5% Indonesia, Brazil, Pakistan, Russia, Bangladesh, Japan, Nigeria Top 10 Most Populous
Replacement Level Fertility = # a couple must bear to replace themselves Developed = 2.1 Developing = 2.5 Total Fertility Rate (TFR) – average # of children a woman will have during her child bearing years (15-49) Developed = 1.6 (2.5 in 1950) Developing = 3.1 (6.5 in 1950) FACTORS THAT INDICATE POPULATION GROWTH: Even if each of today’s couples had an average of 2.1 children, the population would continue to grow for 50+ years because of: population momentum
The growth rate for the US in the year 2000 was close to 1% (~40-50% of the growth is due to immigration into the country) CURRENT POPULATION = over 300 million The US will double in size in the next 70 years. It is currently growing faster than any other developed nation. The TFR (total fertility rate) as a whole for the US is at replacement level = 2. 1 United States Population Statistics The period following WWII saw a spike in birth rate known as the baby boom.
POPULATION AGE STUCTURES: Rapidly expanding populations: Have large number of pre-reproductive individuals and thus have population momentum.
Pre-Industrial = high BR + high DR (low pop growth) Transition = high BR + low DR (rapid pop growth) Industrialized = low BR + low DR (low pop growth) 1)Access to birth control 2) decline in infant mortality 3) Increased education & jobs for women
What Affects Birth Rate & Fertility? Education, employment, & status of and for women Infant mortality rate Availability of contraceptives Religious & social beliefs The importance of children as a part of the work force. Urbanization – tend to have fewer children Cost of raising and educating children. Average age of marriage.
What Factor’s Affect Death Rates? 1)Increased Food Supply & Distribution 2)Better Nutrition 3)Medical improvements/Technology – vaccines & antibiotics 4)Safe Water Supplies (decreases spread of disease) 5)Increase in sanitation and personal hygiene DECREASES DEATH RATE: Indicators of overall health of a country: Life Expectancy – average # of years a newborn infant can expect to live & Infant Mortality - # of infants out of 1000 who will die within one year A low infant mortality indicates good nutrition & safe drinking water (low rate of disease) Global Life Expectancy has increased from 48 to 66 in the last 55 years.