The Human Population

World Population

2200

2047

2024

2012

1999

1987

1975

1960

1930

1830

What Kept the Human Population in Check For

So Many Centuries?

• Disease!

• Smallpox, Diptheria, Measles & Scarlet fever kept the child population down

• Tyhus, Cholera and the Black Plague (14th century) kept the adult population in check

Why the Explosion?

• Discovery of infectious agents• Production of vaccines• Discovery of penicillin• Treatment of sewage

World Population Growth Rate and Absolute Growth

Why is Growth Rate Decreasing?

• Lower fertility rates• 5.0 in 1960 to 2.7 kids/woman

today

United Nations Population Projections

& Fertility Rates

Economic Divisions of the World

Different Worlds• High-Income, Developed/Industrialize

• 971 million, 2003• Gross national income per capita (GNI) = >$9386, average

$28 550

• Middle-Income, Moderately developed• 3 billion• GNI = $766-$9385, average = $1920

• Low-Income, Developing countries• 2.3 billion• GNI < $765, average = $450

Fertility• 98% of world population growth is occuring in

developing countries!

• A fertility rate of 2.0 will ensure a stable population if we ignore infant and child mortality, and women who do not reproduce

• Replacement-level fertility is actually 2.1 in developed countries and higher in developing countries due to the above factors

• Fertility rates in developed countries now averages 1.6 (lowest = 1.3), whereas in developing countries it averages 2.9 (highest 4.0)

• Doubling time with a fertility rate at 1.6 is 700 years

• Doubling time with a fertility rate of 2.7 is 58 years

Population Growth in Developed & Developing

Countries

Rural Populations in Developing Countries

• What is happening to populations based on small-scale agriculture?

• What options do they have to survive?

1. Reform the system of land ownership2. Intensify cultivation3. Open up new land to farm4. Engage in illicit activities for income5. Emigrate (legally or illegally)6. Move to cities & seek employment

City Growth

4035302520151050

Comparing Age Structure in the USA

1985, 2005, 2050

Comparing Age Structure in Italy

Comparing Age Structure in a

Developing Country

This projection is based on the assumption that there will be a decline in fertily rate from 4.8 to 2.7 by 2025

Comparing Projected Populations

2005

2050

Homework

• Answer question 12 in the back of the chapter, to be handed in for a mark for next week.

• This will be marked like a free-response question on your AP exam, only I will be marking you more severly as you will have more time to answer and the book to help you

• Do not use words like « it » and « they »