Human Populations

Section #1:Studying Human

Populations

China Beach

Demography:

•the study of human populations• looks at the historical size (the

past population), economics, social structure, & make-up (race, religion, gender, etc.)

•usually done by country

Developed vs. Developing

•demographers usually group countries based on similar population trends

•developed countries tend to grow more slowly than developing countries

Exponential Human Growth

•Growth rate increased rapidly each decade since the 1800s

•Mainly from increases in food production & improvements with hygiene (industrial & scientific revolutions)

•Earth can’t sustain this growth much longer

Population Pyramids

Forecasting Population Size

•Will our area need more schools or more retirement communities in the next 25 years?

•Will more people move in creating a greater demand for roads & utilities?

Age Structure

•predictions are made on the distribution of ages in a specific population at a certain time

•graphed in a population pyramid that looks like a two-sided bar graph

Population Pyramids

Survivorship

•the % of members of a group that are likely to survive to any given age

•demographers predict this by studying a group of people born at the same time & looks at when each person dies

Survivorship Curves

•Type I Curve = most members in that population survive to be very old

•Type II = similar death rate at all ages (some die younger, others older)

•Type III Curve = many children die

Survivorship Curves

Fertility Rates

•the # of babies born each year per 1000 women in a population

•demographers also look at total total fertility ratesfertility rates = the average # of children a woman gives birth to in her lifetime

Historical Total Fertility Rates for the U.S.

Replacement Level

•the average # of children each parent must have in order to “replace” themselves in the population

•≈2.1 (slightly more than 2) because not all children born will survive & reproduce

Migration

•even in the event that total fertility rates drop below the replacement level (like they did in the U.S. in 1972), a population can still continue to grow from the increased movement of individuals from another area

Immigration vs. Emigration

•immigration = movement into an area

•emigration = movement out of an area

Declining Death Rates

•adequate food•clean water•safe sewage disposal•vaccines•improved healthcare•sanitation

Life Expectancy

•the average # of years a person is likely to live

•most affected by infant mortality•1900 – worldwide life expectancy was 40 years & infant mortality was very high

•2000 – worldwide life expectancy is now 67 years & infant mortality much lower

Life Expectancy

Infant Mortality

•depends on a parent’s access to education, food, fuel, & clean water

•expensive medical care is not necessary – babies that are well fed, kept clean & warm have a better chance of surviving

Demographic Transition

•a model that shows changes in a developed country’s population

•question? How can a population quadruple in a single century & then stop growing?

•theory – industrial development causes economic & social progress that affects population growth rates

Stages of Transition

1. pre-industrial conditions (birth & death rates high, population stable)

2. population explosion (death rates decline while birth rates remain high)

3. population growth slows (birth rates decrease to match the death rate) & population size stabilizes

4. population size begins to decrease as the birth rate drops below the replacement level

Why are Birth Rates Declining?

• increasing education of women• increasing the economic

independence of women• when women learn how to help

their babies survive, they do not need to bear as many + large families may be a financial burden rather than an asset

Four Stages of Transition