Announcements Quiz on Friday January 14 th Extra Credit: Check Stern MASS website – Each project is worth up to 0.5 pts added to a previous EXAM. – Each student may do up to 2 (independently!!) – Due January 21, 2011

Human Population January 12, 2011

Declining Death Rates The dramatic increase in Earth’s human population in the last 200 years is because death rates have declined more rapidly than birth rates.

Why has death rate declined? More people have access to: – Adequate food – Clean water – Safe sewage disposal

Life Expectancy Def: The average number of years members of a population are likely to live

Infant Mortality Life expectancy is most affected by infant mortality, the death rate of infants less than one years old. Infant health is affected by the parents’ access to education, food, fuel, and clean water.

Life Expectancy By Region

Life Expectancy New threats arise as populations become denser. AIDS and Tuberculosis are a concern in places where disease can spread quickly.

The Demographic Transition

Demographic Transition Def: A model that describes how economic and social changes affect population growth rates. There are 4 stages of the transition

Stage 1: Preindustrial Birth Rate: High Death Rate: High Population Size: Stable

Stage 2: Transitional Population Explosion Occurs! Death Rates: Decline (hygiene, water, food). Birth Rates: Remains high

Stage 3: Industrial Population growth slows. Birth Rate: Decreases – Begins to match Death rate Population size stabilizes

Stage 4: Postindustrial Birth Rate: Drops below replacement level birth rate. Population Size: Begins to decrease.

Using the Figure What is happening to the birth rate and death rate when there is a rapid population growth? What is happening to the birth and death rates when there is zero growth? What is happening to the birth and death rates when population growth is negative?

Using the Figure What is happening to the birth rate and death rate when there is a rapid population growth? – The birth rate is higher than the death rate What is happening to the birth and death rates when there is zero growth? – They are about the same What is happening to the birth and death rates when population growth is negative? – The birth rate is lower than the death rate.

Women and Fertility Total Fertility Rate: – Developed Countries: 1.6 children per woman – Developing Countries: 3.1 children per woman

Changing Population Trends A rapidly growing population uses resources at an increased rate and can overwhelm the infrastructure of a community. Infrastructure: The basic facilities and services that support a community, such as schools and hospitals.

Urban Sprawl

Sprawl uses more land than necessary; has a lower population density than traditional cities and towns (e.g., fewer people in larger houses); creates a dependence on cars for almost everything; results in fragmented open spaces, wide gaps between development, and a scattered appearance;

Sprawl separates uses into distinct areas (so, you don't usually have a store or a movie theater within walking distance from your home); is characterized by repetitive one-story commercial buildings surrounded by acres of parking; and.