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

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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