1. Environmental Science
Chapter 9 Lecture Notes
The Human Population
Introduction to Human Population Growth (11")

2. Chapter 9 Targets
1. I can define demography and describe the 2 general categories of population growth they study.
2. I can describe how the size and growth rate of the human population has changed in the last 200 years.
3. I can make predictions about population trends based on age structure.
4. I can describe how survivorship, fertility, migration, death rate and life expectancy affect populations.
5. I can describe the four stages of the demographic transition.
6. I can name the 2 main factors affecting birth rates.

3. Studying Human Populations
Demography: study of HUMAN populations
Countries based on 2 population trends:
Developed and Developing countries.
Developed countries have:
 average incomes
 industrial economies
 social support systems
 population growth
Developing countries have:
 average incomes
simple and agriculture-based economics
 population growth T1

4. The Human Population Over Time
Human population underwent exponential growth in the 1800s. WHY?
Better food production and hygiene came with the industrial and scientific revolutions

5. Age Structure T3
Age structure/Population Pyramid: classifies a population into groups by age age
helps demographers make predictions
Countries with high growth rates usually have more young than old people
Countries with slow growth or no growth usually have an even distribution of ages in the population
Ethiopa
Russia
United States

6. Survivorship T4
Survivorship: % of newborns in population expected to survive to a given age
used as another way to predict population trends
(see video)
Which survivorship curve would belong to humans? Frogs? Robins?

8. Fertility Rates T4
Fertility rate: number of births (per year) per 1,000 women of childbearing age (usually 15 to 44)
Replacement level: average number of children each parent must have in order to “replace” themselves
This number is slightly more than 2 because not all children born will survive and reproduce

9. Migration T4
Migration: movement of individuals or populations from one location to another
Immigration vs. Emigration
Populations of many developed countries might be decreasing if not for immigration

10. Declining Death Rates Dramatic  in human population in last 200 years
Happened because death rates declined faster than birth rates
Death rates declined mainly because more people now have access to enough food, clean water, and safe sewage disposal
Discovery of vaccines in 20th century also contributed to declining death rates

11. Life Expectancy T4
Life expectancy: average length of time an individual is expected to live
Life expectancy is most affected by infant mortality, the death rate of infants less than a year old

12. The Demographic Transition
Demographic transition: general pattern of demographic change from high birth/death rates to low birth/death rates
Seen during history of more-developed countries
Stages of Demographic Transition Video (1")

13. Stages of Transition First stage: society is preindustrial
Birth/death rates are high and population size is stable
Second stage: population explosion occurs
Death rates decline as hygiene, nutrition, and education improve. Birth rates remain high, so population grows very fast.
Third stage: population growth slows because birth rate decreases
Birth rate = death rate, population size stabilizes
Fourth stage: birth rate drops below replacement level, population begins to decrease

14. Women and Fertility T6
The factors most clearly related to a decline in birth rates are increasing education and economic independence for women

15. Chapter 9 Targets
7. I can describe three problems caused by rapid human population growth.
8. I can compare population growth problems in more-developed countries and less developed countries.
9. I can analyze strategies countries may use to reduce their population growth.
10. I can describe worldwide population projections into the next century.

16. Problems of Rapid Growth
Rapidly growing population uses resources faster than environment can renew them
Living standards drop when wood is removed from local forests faster than it can grow back, or when wastes overwhelm local water sources
Symptoms of overwhelming populations include polluted rivers, barren land, inadequate housing, and overcrowded schools

17. A Demographically Diverse WorldT8
Least developed countries: identified by U.N. as showing fewest signs of improving income, human resources, and economic diversity
Populations are still growing rapidly in less developed countries, with most of the world’s population now in Asia

18. Managing Development and Population Growth
Less developed countries face continued population growth that will prevent them from developing into world economic leaders
Countries such as China, Thailand, and India have created campaigns to reduce fertility rates of their citizens
These campaigns include public advertising, family planning programs, economic incentives, or legal punishment

19. Managing Development and Population Growth
In 1994, United Nations held International Conference on Population and Development (ICPD)
Involved debates about relationships between population, development, and the environment

20. Managing Development and Population
With these goals, worldwide fertility rates are dropping as shown below (see assignment)

21. Projections to 2050
T10
Looking at the graph below, most demographers predict the medium growth rate, and a world population of 9.2 billion in 2050
Current population is at 7 billion
Population Clock