1. Chapter 21, Population, Urbanism and the Environment Key Terms

2. Demography The scientific study of the current state and change over time in the size, composition, and distribution of populations. Census A head count of the entire population of a country.

3. Vital statistics Information about births, marriages, deaths, migrations in and out of the country, and other fundamental quantities related to population. Immigration Migration into a society from outside.

4. Emigration Departure of people from a society. Crude birth rate Number of babies born each year for every 1,000 members of the population.

5. Death rate The number of deaths each year per 1,000 people. Infant mortality rate The number of deaths per year of infants less than one year old for every 1,000 births.

6. Life expectancy The average number of years a population or group is expected to live. Sex ratio The number of males per 100 females, or the number of males divided by the number of females.

7. Age-sex pyramid Graphic representation of the age and gender structure of a society. Cohort Consists of all the persons born within a given period.

8. Malthusian theory Theory that a population tends to grow faster than the subsistence needed to sustain it. Demographic transition theory Proposes that countries pass through a predictable sequence of population patterns linked to the degree of technological development in the society, ending with a situation in which the birthrates and death rates are both relatively low.

9. Population replacement level A state in which the combined birthrate and death rate of a population simply sustains the population at a steady level, called the equilibrium level. Urbanism The extent to which a community has the characteristics of city life and the “urban” end of the rural–urban continuum.

10. Population density The number of people per unit of area. Human ecology The scientific study of the interdependencies that exist between humans and their physical environment.

11. Human ecosystem. Any system of interdependent parts that involves human beings in interaction with one another and the physical environment. Greenhouse effect Rise in the earth’s surface temperature caused by heat trapped by excess carbon dioxide in the atmosphere.

12. Thermal pollution Heating up the earth's lakes and rivers as the result of the chemical discharges of heavy industry. Environmental racism Consists of dumping of toxic wastes with disproportionate frequency in areas that have high concentrations of minorities and persons of lower socioeconomic status.

13. Ecological demography Combines the studies of demography and ecology. Ecological globalization The worldwide dispersion of problems and issues involving the relationships between humans and the physical and social global environment.