Populations Population- group of individuals of the same species occupying a given area Increase –Birth –Immigration Decrease –Death –Emmigration

Populations Change Populations increase –Birth rate > Death Rate –Immigration > Emmigration Populations Decrease –Birthrate < Death Rate –Immigration <Emmigration

Exponential Growth r = Net Reproduction per individual Growth = (r) x (N)umber of individuals –Ex: Bacteria: r = 100% per ½ hour –Ex: Humans: r = 2-5% /yr Doubling Time- Length of time it takes for a population to double in size

Exponential Growth

Notes on Exponential Growth The more of something there is, the more it can produce. Population Growth Must be Limited –Limiting Factors Food Space Predators Disease Polluted Environment

Carrying Capacity (K) Carrying Capacity (K)- Maximum number of individuals of a population that a given environment can sustain This leads to Logistic Growth

Overshooting K

History of Human Population

Poverty The countries that have the highest population growth are the ones least capable of dealing with it. –In developing nations, children are still an asset, not a liability –In 1999, the richest 20% possessed 82 times the income of the poorest 20% –The richest 20% used 86% of the world’s resources, leaving 14% for the other 80%

Demography Demography (‘People’ ‘Measure’)- encompasses vital statistics about people, such as births, deaths, number of males and females, age structure, as well as total population size. Age Structure- How many people of there are of various ages

Fertility and Birth Rates Fertility- Births per woman Total Fertility Rate- number of children born to an average woman in a population during her entire reproductive life

Zero Population Growth (ZPG) Zero Population Growth (ZPG) occurs when births plus immigration in a population just equal deaths plus emigration –When infant mortality is high, total fertility rate needs to be about 4 or 5 to reach ZPG –When mortality is low, as in more highly developed countries, the rate needs to be about 2.1 to reach ZPG.

Don’t Forget the Footprint

Two Problems Increasing Ecological Footprints in the rest of the world mean less resources and more poverty Immigration to developed nations means more big Ecological Footprints and using more resources