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A Changing Human Population


A Changing Human Population Environmental Science – PowerPoint PPT presentation

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Title: A Changing Human Population

A Changing Human Population
  • Environmental Science

Studying Human Populations
  • Demography the study of the characteristics of
    populations (usually human populations)
  • Countries are divided into 2 categories by
  • Developed higher average incomes, slower
    population growth, diverse industrial economies
  • Developing lower average incomes, rapid
    population growth, agriculture-based economy

Forecasting Population Size
  • Demographers try to predict what will happen to a
    population in order to plan for future
    infrastructure and services
  • Demographers look at several different factors to
    make their predictions

Age Structure
  • Age structure describes the distribution of ages
    of a population
  • Countries with high growth rates have more young
    people than old people
  • Countries with slow growth or no growth have an
    even distribution of ages in the population

  • The percentage of members of a group that are
    likely to survive to a given age
  • To predict survivorship, demographers study a
    group of people born at the same time and notes
    when each member of the group dies.

Fertility Rates
  • The number a babies born each year per 1000 women
    of childbearing age (15-44)
  • Replacement level the average number of
    children parents must have to replace

Declining Death Rates
  • Increased access to food, clean water, and safe
    sewage disposal have lead to a decrease in the
    world death rate
  • This decrease has more to do with the huge
    increase in the human population than the birth

  • Migration in general, is any movement of
    individuals or populations from one location to
  • The populations of many developed countries might
    be decreasing if not for immigration.

Declining Death Rates
  • The dramatic increase in Earths human population
    in the last 200 years has happened because death
    rates have declined more rapidly than birth
  • Death rates have declined mainly because more
    people have access to adequate food, clean water,
    safe sewage disposal, medicine/health care.
  • The discovery of vaccines in the 20th century
    also contributed to the declining death rates.

Life Expectancy
  • The average number of years that a member of a
    population is likely to live
  • Infant mortality rates have the largest influence
    on life expectancy numbers
  • Better medical care has lead to higher life
    expectancy in developed and developing nations.

Demographic Transition
  • The demographic transition is the general pattern
    of demographic change from high birth and death
    rates to low birth and death rates.
  • Industrial development causes economic and social
    progress that then affects population growth

Women and Fertility
  • A decline in birth rates can most clearly be
    related to increasing education and economic
    independence for women (jobs).
  • Educated women learn family planning techniques
    and find that they do not need to bear as many
    children to ensure that some will survive.
  • Women are able to increase the prosperity for
    their families while spending less energy bearing
    and caring for children.
  • Educated women delay child bearing.
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