Ch 9 The Human Population

Demography• The study of populations

Demographics – into 2 categories

Developed Countries- Ex. United states- Have higher

average incomes- Slower population

growth- Diverse industrial

economies

Undeveloped Countries- Ex. South Africa- Have lower average

incomes- Simple and

agriculture-based economies

- Rapid population growth

-

Exponential Growth

• Population growth rates increased during each decade

• Due to increases in food productions and improvements in hygiene with industrial/scientific revolutions.

Age Structure Diagrams

Forecasting Population Size• Demographers

looks at these properties to predict population changes:

1. Age Structure2. Survivorship3. Fertility Rates4. Migration

1.Age Structure = the age distribution of ages in a specific population at a certain time. • Age Structure

Diagram = Type of double sided bar graph

• Typically the more young people than older people leads to an increase in population size.

2. Survivorship• = the percentage

of members of a group that are likely to survive to any given age.

• Demographers study groups of people born at the same time and notes when each person dies.

• Type I – Wealthy countries like Japan and Germany bc people live to old age.

• Type II – populations have similar death rate at all ages.

• Type III – Poor countries in which many children die early.

3. Fertility Rates• = the number of

babies born each year per 1,000 women in a population.

• Total fertility rate = average number of children a woman

gives birth to in her lifetime.- Replacement Level =

• Replacement Level = the average number of children each parent must have in order to “replace” themselves.

• The average is about 2.1 (since not all children will survive)

4. Migration• = “the movement of

individuals between areas” • Two types:• 1. Immigration –

movement into an area• 2. Emigration –

movement out of an area

• Quick check:The population of the U.S. and other developed countries might be DECREASING if not for which?

Immigration!

Declining Death Rates• The dramatic

increase in Earth’s human population in the last 200 years has happened because death rates have declined more rapidly than birth rates.

• Reasons:1. Access to

adequate food2. Access to

clean water3. Safe sewage

disposal

Question:

• Look at the chart on page 238 Figure 7

What kind of regions have the highest life expectancies?MORE DEVELOPED

COUNTRIES

Life Expectancy• “the average number

of years members of a population are expected to live”

• Most affected by:INFANT MORTALILTY RATE

= “THE DEATH RATES OF INFANTS LESS THAN 1 YEAR OLD”

IN 1900, WORLD WIDE LIFE EXPECTANCY WAS ABOUT 40 YEARS AND THE INFANT MORTALITY RATE WAS VERY HIGH. BY 2000, THE RATE OF INFANT MORTALITY WAS LESS THAN 1/3 OF THE RATE IN 1900

LIFE EXPECTANCY AVERAGE:

AVERAGE = 67 YODEVELOPED COUNTRIES = 80YO

Infant mortality rate• Most affected by

parents’ access to:1. education2. Fuel3. Food4. Clean water

*notice it is NOT health care!

New Threats to life expectancy:

…CONTAGIOUS DISEASES!

TuberculosisAIDS

*South Africa’s life expectancy has been reduceddue to an AIDS epidemic

What do we need for our populations?

The Demographic Transition

• “A model that describes how economic and social changes affect population growth rates.”

• It has 4 stages:

4 stages of Demographic Transition

Stage 1

• “Preindustrial”• Birth and death

rates are about equal• Most of the world

was here until 1700 when stage 2 hit.

Stage 2

A Population explosion occurs! (may double in ≥ 30 years)

• Death rates decline: due to hygiene, nutrition, and education improve.

Birth rates remain high, so the population grows quickly!

Stage 3

• Birth rate decreases

• Populations begin to stabilize

• But the population has quadrupled in size due to the transition.

Stage 4: “postindustrial”

• The birth rate drops below replacement level, so the size of the population begins to decrease.

• This has taken 1-3 generations to occur in a developed country.

Women and Fertility

• Factors that lead to decline in death rates:

1. increasing education2. economic independance

Education:• Educated women

KNOW they don’t need lots of kids in case a few will die.

• Family planning

$ brings freedom- Contribute to family- Spend less energy

bearing/caring for kids

Why large families?

Traditionally:• Some communities

children work• Kids take care of

elderly

Modernization:1. If women work, kids need daycare which is expensive, so less is better.2. Working creates PENSIONS so elderly support themselves.

This is lowering the birth rate!

Current Total fertility rates…

Developed:1.6 children per woman

Developing Countries:3.1 Children per woman