Unit 3: Human Population

The Anthropocene Epoch

• Is named for the alterations to the Earth’s crust as a result of human activity– Industrial Revolution– Atomic Age

World Population

• Is 7.1 billion people• Has increased exponentially

over the past 10,000 years• Has stopped growing as

quickly– May start decreasing by 2100

Human Carrying Capacity of the Earth

• Is estimated between 4 and 16 billion

• Depends on how we use resources

• Depends on how quickly the population grows

Age Structure

• Expresses how a population is divided among age groups

• Can show how a population is and will be affected by birth rates and life expectancy

Demographic Transition

• Is a change in birth and death rates over time

• Occurs as nations industrialize

• Overall leads to a decline in population growth

Demographic Transition

• Stage 1– Birth and death rates are

high– Population is stable

Demographic Transition

• Stage 2– Death rates drop due to

improvements in medical care and sanitation

– Birth rates remain high– Population grows

Demographic Transition

• Stage 3– Birth rates drop due to

increased education and better employment

– Population growth rate slows

Demographic Transition

• Stage 4– Birth and death rates

remain low due to economic stability

– Population stays stable

Demographic Transition

• Stage 5– Birth rates drop below

death rates– Population declines

Life Expectancy Affects Population Growth

• Longer-lived individuals delay having children– Can result in fewer children per couple

• Increased numbers of older individuals can become a burden on younger members of a population

Disease Affects Population Growth

• Epidemics like influenza can increase the death rate• Diseases like AIDS can decrease life expectancy

Birth Rates Affect Population Growth

• Total Fertility Rate (TFR)– Estimated number of children each woman in a population

will have

• If this number drops below the number of children needed to replace their parents, the population will shrink

Birth Rates Affect Population Growth

• Replacement-Level Fertility– # of births required to offset deaths– Must take into account pre-

reproductive mortality• Individuals who die before reproducing

– In developed nations, it is 2.1– In developing nations, it is higher

Migration Affects Population Growth

• Only occurs between countries, not the planet

• A positive migration indicates a country’s population is growing– More people are entering

the country than leaving it

Achieving Zero Population Growth

• Depends on controlling birth rates– Education (sex education

and general education)– Access to birth control– Delaying age of first

childbearing