The Human Population Chapter 9

9.1 Studying Human Populations

Page 235-240

Studying Human Populations Introduction

• In 20th century human population on Earth grew faster than ever.

• Rapid growth led to environmental problems• Demography is the study of human populations. • Developed countries: high income, slow growth,

diverse industrial economies.• Developing countries: lower income, simple and

agricultural based economies, and rapid population growth.

Human population over time

• In 1800’s population grew rapidly.

• Exponential growth occurred each decade.

• Why? Food, hygiene, from industrial and scientific revolutions

• Earth is unlikely to sustain exponential growth forever. See figure 1 pg 235

Forecasting Population Size• Demographers try to predict

changes in 4 ways.

• 1.Age Structure: the distribution of ages in a specific population at a certain time. – What will happen if more

young than old?

• Age is graphed in a population pyramid. See Figure 2.

Continued…• 2.Survivorship: the

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

• Demographer studies a group of people born at same time and notes when each person dies.

• See Survivorship curve Figure 3. Types 1,2,3

Continued….• 3. Fertility Rates: The number of babies born

each year per 1,000 women in a population. • Also calculate total fertility rate or average

number of children a woman gives birth to.• Replacement level is the average number of

children each parent must have to replace themselves in a population. 2:1

• See Figure 4

continued

• Growth is also due to immigration….

• 4. Migration: The movement of individuals between areas.

• In –immigration

• Out- emigration

• See Figure 5

Declining Death Rate

• Increase in human population in last 200 years is also due to decline in death rates.

• Why? Adequate food, clean water, safe sewage disposal, & vaccines

• Life expectancy: The average number of years members of a population are likely to live.

• New threats rise as populations become denser… AIDS, tuberculosis…

The Demographic Transition

• Demographic transition: is a model that describes how economic and social changes affect population growth rates.

• Based on observations of history.

• See figure 8. Compares birth, death, population sizes…

• There are 4 stages

4 stages of demographic transition

• 1. Preindustrial = Birth high, death high, population stable.

• 2. Population Explosion= death low, birth high, population double (hygiene, nutrition, education improve).

• 3. Population growth slows = birth and death equal, population stable

• 4. Birth drops below replacement = population decreases

Women and Fertility• Decline in birth are due to education

and economic independence for women.

• Don’t need to bear as many children to survive, Family planning techniques, work to contribute to family…

• Child care is expensive if work away from home, pensions for elderly….

• Developed countries 1.6 kids per woman

• Developing countries 3.1 kids per woman

Do questions pg 240 1-4

• Active Reading Book page 43