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5-3 Human Population

Growth

5-3 Human Population Growth

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Historical Overview

Historical Overview

Like the populations of many other living

organisms, the size of the human

population tends to increase with time.

For most of human existence, the population

grew slowly.

Limiting factors kept population sizes low.


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Historical Overview

About 500 years ago, the human population began

growing more rapidly.

Life was made easier and safer by advances in

agriculture and industry.

Death rates were dramatically reduced due to

improved sanitation, medicine, and healthcare,

while birthrates remained high.


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Historical Overview

With these advances, the human population

experienced exponential growth.

Human Population Growth


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Patterns of Population Growth


The scientific study of human populations is called

demography.

Demography examines the characteristics of

human populations and attempts to explain how

those populations will change over time.


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Birthrates, death rates, and the age

structure of a population help predict

why some countries have high growth

rates while other countries grow more

slowly.


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The Demographic Transition

Over the past century, population growth in the

United States, Japan, and much of Europe has

slowed dramatically.

According to demographers, these countries have

completed the demographic transition, a

dramatic change in birth and death rates.


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The demographic transition has three stages.

In stage 1, there are high death rates and high

birthrates.

In stage 2, the death rate drops, while the birthrate

remains high. The population increases rapidly.

In stage 3, the birthrate decreases, causing

population growth to slow.


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The

demographic

transition is

complete when

the birthrate

falls to meet the

death rate, and

population

growth stops.


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Age Structure

Population growth depends, in part, on how many

people of different ages make up a given

population.

Demographers can predict future growth using

models called age-structure diagrams.

Age-structure diagrams show the population of a

country broken down by gender and age group.


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In the United

States, there are

nearly equal

numbers of people

in each age group.

This age structure

diagram predicts a

slow but steady

growth rate for the

near future.

Males Females

8 6 4 2 0 2 4 6 8

Percentage of Population

80+

60–64

20–24

0–4

40–44A

ge (

years

)

U.S. Population


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In Rwanda, there are many more young children than teenagers, and many more teenagers than adults.

This age structure diagram predicts a population that will double in about 30 years.

80+

60–64

20–24

0–4

Ag

e (

years

)

Males Females

Rwandan Population

40–44

Percentage of Population


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Future Population Growth


To predict human population growth,

demographers must consider the age structure of

each country, as well as the prevalence of life-

threatening diseases.

If growing countries move toward the demographic

transition, growth rate may level off or decrease.


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Ecologists suggest that if growth does not slow

down, there could be serious damage to the

environment and global economy.

Economists assert that science, technology, and

changes in society may control the negative impact

of population growth.

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5-3

Resources/ch05_sectn03_quiz.qtb








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5-3

The size of the human population began to

increase exponentially after the

a. bubonic plague.

b. development of plowing and irrigation.

c. Industrial Revolution.

d. development of the first cities.

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5-3

Which of the following is NOT a potential limiting

factor of human population growth?

a. famine

b. medicine

c. war

d. disease

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5-3

After the demographic transition is complete, a

population

a. grows rapidly.

b. grows slowly.

c. begins a period of rapid decline.

d. stays about the same size as time passes.

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5-3

An age-structure diagram shows a breakdown of

a population by

a. location and age group.

b. age group and gender.

c. birthrate and death rate.

d. age group and emigration rate.

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5-3

Since the mid-1960s, the average annual growth

rate of the human population has

a. remained about the same.

b. failed to show a consistent pattern.

c. increased.

d. decreased.

END OF SECTION

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