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