Examining the composition of a population

1. Examining the composition of a population • What do we mean by the “composition of a population”? • What is the composition of the population of our classroom right now?

2. Population Pyramid A bar graph that shows the age and gender composition of a population. A population pyramid provides valuable clues about how a population might change.

3. Population Pyramid cont. • On the population pyramid the left side shows the males while the right side shows the females. • http://www.edugen.com:30120/geodiscoveries/resources/ch33/print/population_pyramids1/index.htm • http://www.edugen.com:30120/geodiscoveries/resources/ch33/print/population_pyramids2/index.htm

4. Age Dependency Ratio • Age dependents are people under 15 and over 65. They are called age dependents because most of them don’t work full time. • The age dependency ratio helps a country predict and plan for the future. • The age dependency ratio is the number of people over 65 and under 15 as a proportion of the working age population. • Why do we need to examine this population?

5. Sex Ratio • The sex ratio is the proportion of males to females in a population • The natural sex ratio is 105:100. This means that there are 105 boys born to every 100 girls • How does our class measure up to this ratio?

6. Rate of Natural Increase • When does a population increase? • The rate of natural increase is the percentage of annual growth in a population (not including migration) • To calculate the RNI demographers subtract the death rate from the birth rate and convert it to a percentage.

7. Demographic Transition Model • How does the demographic transition model compare to the gapminder website? • What are the limitations of a Demographic Transition Model • Why do we need to consider migration?

8. Malthusian Population Theory • Thomas Malthus – 1798 • Food supply increased arithmetically 1,2,3,4 • Population increased geometrically 1 to 2 to 4 to 8 to 16 • So what’s the problem with this? • He proposed that when the population exceeded the food supply positive checks such as famine, disease would bring balance.

9. Malthusian theory cont. • Malthus also proposed that people should implement voluntary preventative checks like postponing marriage and practicing sexual restraint. • Why was this such a radical idea?

10. Neo-Malthusians (modern Malthusians) • The world has a carrying capacity. This means that the world can only support a certain number of people. • What are the criticisms of this theory

11. Cornucopians • Ester Boserup proposed that with more people to provide labor, food production could be increased. • A cornucopia is a horn of plenty. Boserup’s theory was called the cornucopian theory because it was like a horn of plenty.

12. Food Insecurity • Food insecurity is when people don’t have physical or financial access to basic foodstuffs • Conditions leading to food insecurity are • Poverty • Population growth • War • Civil strife • Natural resource constraints • Environmental degradation • Natural disasters

13. Food Insecurity cont. • The Famine Early Warning System was initiated by the U.S Department of Agriculture. It’s purpose is to examine trends that might lead to famine. • Look figure 3.12.