Chapter 6 (week 2)
IPAT model: It is variation of a formula proposed in 1974 by Paul Ehrlich and John Holdren, a
professor of environmental policy at Harvard University. The IPAT model represents how out
total impact (I) on the environment results from the interaction among population (P), affluence
(A), and technology (T): I = P x A x T
Demography: The application of population ecology principles to the study of statistical change
in human populations is the focus of the social science of demography.
The first transition happened in the Palaeolithic period (or Old Stone Age).
Agricultural revolution: The second major change. This change began to occur around 10 000
to 12 000 years ago and is known as the agricultural revolution, in what is known as the
Neolithic (or New Stone Age) period.
Industrial revolution: The third major societal change. Known as the Industrial Revolution,
began in the mid-1700s.
Medical-Technology revolution: We currently in the midst of a fourth major transition,
involving the globalization of modern medical and technology advancements. The medical-
technology revolution is marked but developments in medicine, sanitation, and pharmaceuticals.
Demographers: Study population size, density, distribution, age structure, sex ratio, and rates
of birth, death, immigration, and emigration of humans, just as population ecologists study
these characteristics in other organisms.
Population density: The number of people per unit of land area-is particularly high in regions
with temperate, subtropical, and tropical climates, such as China, Europe, Mexico, southern
Africa, and India.
Total fertility rate (TFR):The average number of children born per female member of a
population during her lifetime.
Replacement fertility: The TFR the keeps the size of a population stable. For humans,
replacement fertility is equal to a TFR. When the TFR drops below 2.1, population size, in the
absence of immigration, will shrink.
Natural rate of population change: Chang