The Human Population

1. The Human Population Ch. 9, Section 1: Studying the Human Population Standards: SEV5a, b

2. What is demography? • Demography- study of populations, especially human populations. • Includes study of: • Historical size of population • Make up of population • Economics • Social structure • Demographers use this info. to make comparisons & predictions about populations.

3. What 2 categories do demographers group countries into? • Developed Countries • Have higher avg. incomes • Slower pop. growth • Diverse industrial economies • Ex: US, western Europe

4. What 2 categories do demographers group countries into? • Developing Countries • Lower avg. incomes • Simple, agricultural based economies • Rapid population growth • Ex: India, China, countries in Africa

5. How has the human population changed over time? • Population grew slowly for 1000’s of years • In 1800’s (Modern Age) population grew exponentially • Due to increase in food supply & better hygiene thanks to industrial & scientific revolutions • Human population continues to grow exponentially… will it ever reach its carrying capacity?

6. How can a population be predicted? • Demographers look at many properties of populations to predict: • Will community need more schools? • Will community need more retirement homes • Will population increase to point where we need more roads & utilities?

7. How can a population be predicted? • Demographers use numerous tools and graphs to predict populations: • Age structure graphs • Survivorship curves • Fertility rates • Migration patterns

8. Age Structure Graphs • Graph that shows the distribution of ages in a specific population at a certain time. • A.K.A. population pyramids • Parts of an age structure graph: • Bars = ages • Colors = gender • Numbers on bottom= percentage of the population • 3 Categories of Age Structure Graphs • Rapid growth • Slow growth • Declining/zero growth

9. Age Structure Graphs • Rapid growth • Young people dominate population • Has population momentum- more children will move up to become reproductive • Rapid increase in birth rates once the youngsters reach reproductive age. • EX: Developing countries- many countries in Africa, Mexico, S. America

10. Age Structure Graphs • Slow Growth • Birth rates = death rates • All age groups are about equal • EX: Most Western European countries, U.S.

11. Age Structure Graphs • Declining Growth (Zero growth) • Birth rates are lower than death rates • Many more older people who are not reproducing • Fewer younger people • Population will become much smaller when they die. • Ex: Germany, Russia

12. Survivorship Curves • Percentage of members of a group that are likely to survive to any given age. • Follows a group of organisms from the time they were born to the time they die to see trends. • 3 Types of Survivorship curves: • Type I • Type II • Type III

13. Survivorship Curves • Type I • Lots of offspring survive and live to old age. • Ex: Developed countries- US, Japan • Ex: Zebras, Bears, etc. • Type II • Populations have a similar death rate at all ages • Ex: birds • Type III • Lots of offspring die young & very few survive to old age. • Ex: Developing countries- Africa, Asia • Ex: insects, clams

14. Fertility Rates • Fertility rate- number of babies born each year per 1,000 women in a population. • Total fertility rate- avg. number of children a woman gives birth to in her lifetime. • Replacement level fertility- avg number of children each parent must have in order to “replace” themselves in the population. • RLF = approximately 2 children • Compare Zambia to Europe using the chart to the right. • What conclusions can you draw based on this data?

15. Fertility Rates • Keeping total fertility rate below replacement level fertility will help populations decline. • This graph shows US population change since 1920. • Who are the baby boomers? Lots of babies were born post WWII…when soldiers returned home from war ;) • Why did population start rising in the 1990’s? Children of baby boomers were growing up & having kids

16. Migration Patterns • Immigration- movement into an area • Emigration- movement out of an area • US experiences lots of immigration… would our population decline if we didn’t have immigration?

17. What factors affect a country’s death rate? • Life expectancy- avg. number of years members of a population are likely to live. • Most affected by infant mortality- death rate of infants less than a year old. • Infant mortality (death rates) have decreased and life expectancy has increased due to access to • adequate food • clean water • safe sewage disposal • vaccines (around beginning of 20th century) • access to education Worldwide Infant mortality rates

18. What factors affect a country’s death rate? • Threats to life expectancy : • As populations increase, population becomes denser • Disease can spread quickly thru dense populations. • Ex: AIDS, tuberculosis • This will increase death rate and decrease life expectancy. Sign located in South African village.

19. What factors affect a country’s birth rate? • Birth rates typically are lower in areas where: • Women are educated • Academically • Family planning techniques • Women are economically independent • Have jobs • So less time for raising many children. • Pensions are available for elderly • no need for kids to help take care of elderly

20. What factors affect a country’s birth rate? • Large families are common when children are needed to work and take care of older family members • As countries modernize, there is less need for lots of kids. • This can decrease birth rates.

21. What factors affect a country’s birth rate? • Factors that can increase a population’s birth rate: • Lack of birth control due to availability or religion • Need to have children b/c have poor health care and children can die easily • Women are uneducated, repressed, with no rights to make decisions about their own bodies.

22. What is the demographic transition? • Pattern of falling death rates & birth rates due to improved living conditions. • All countries should experience this trend in population change.

23. What are the stages of demographic transition? • Preindustrial societies- • Higher birth rates- due to need for kids to help on farm; have lots of kids because many will die from disease/malnutrition. • Higher death rates- due to food shortages, malnutrition, lack of sanitation & medicine, accidents, other hazards • Population is low because of high death & birth rates.

24. What are the stages of demographic transition? • Industrialization- • Decreasing death rates- due to improved health care and sanitation. • Continuing high birth rates- people still having lots of kids because healthcare is not widespread and may be ignorant about birth control • People have better jobs, more income, more people surviving due to rise in standard of living. • Population grows exponentially.

25. What are the stages of demographic transition? • Mature Industrial • Death rates continue declining • Birth rates begin declining • Women realize they don’t need as many kids • Women realize how expensive kids are • Women may have jobs so less time for kids

26. What are the stages of demographic transition? • Postindustrial societies- eventually BR & DR level out & population is at equilibrium. W. Europe saw this in 19th & 20th century