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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