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Chapter 4.2


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Chapter 4.2

  1. 1. Human Population Chapter 4.2
  2. 2. World Population <ul><li>Census is taken every 10 years </li></ul><ul><li>Demography = the study of human population size, density and distribution, movement and its birth and death rates </li></ul>
  3. 3. Human population growth <ul><li>Human population growth is different from bacteria population growth in that we can consciously change our environment </li></ul><ul><ul><li>ex: we eradicated smallpox </li></ul></ul><ul><ul><li>ex: developed methods for producing more food </li></ul></ul><ul><ul><li>ex: infant mortality rate has decreased </li></ul></ul><ul><ul><li>ex: technological developments improved water quality </li></ul></ul><ul><li>Result = live longer and produce more offspring that live long enough to produce more offspring </li></ul>
  4. 4. Calculating growth rate <ul><li>Determined by many factors: births, deaths, immigration, emigration </li></ul><ul><ul><li>Birthrate : number of live births per 1000 population in a given year </li></ul></ul><ul><ul><li>Death rate : number of deaths per 1000 population in a give year </li></ul></ul><ul><ul><li>Immigration: movement of individuals into a population </li></ul></ul><ul><ul><li>Emigration: movement out of a populations </li></ul></ul>
  5. 5. Calculating growth rate cont. <ul><li>Formula: (version 1) </li></ul><ul><li>(Birth rate + Immigration rate) – (Death rate + Emigration rate) = Population Growth Rate </li></ul><ul><li>Formula: (version 2… used often because immigration and emigration rates are not accurate) </li></ul><ul><li>Birth rate – Death rate = Population Growth Rate (PGR) </li></ul>
  6. 6. Calculating growth rate cont. <ul><li>If birthrate of a population = death rate of a population  then PGR = 0 </li></ul><ul><ul><li>Population is changing, but it is stable </li></ul></ul><ul><li>If PGR > 0, more individuals are entering the population than leaving </li></ul><ul><ul><li>Population is growing </li></ul></ul><ul><li>If PGR < 0, more individuals are leaving than entering </li></ul><ul><ul><li>Populations might start decreasing </li></ul></ul>
  7. 7. The effect of a positive growth rate <ul><li>If PGR = 1.7% in 1995 and then PGR = 1.3% in 2001 </li></ul><ul><ul><li>The world is populating, but just at a slower rate </li></ul></ul><ul><li>Unless GROWTH RATE BECOMES NEGATIVE, the population continues to grow (just not rapidly) </li></ul>
  8. 8. Doubling time <ul><li>Doubling time : the time needed to double in size </li></ul><ul><li>It depends on current population and growth rate </li></ul><ul><ul><li>slow or negative growth rate  it will take a long time </li></ul></ul><ul><ul><li>often called a “developed country” </li></ul></ul><ul><li>If there is a rapid doubling time  often referred to as a “developing country” </li></ul><ul><li>Formula: </li></ul><ul><li>Doubling time (in years) = 70 / annual percent growth rate </li></ul>
  9. 9. Age structure <ul><li>The proportion of the population that are in different age levels </li></ul><ul><li>Age structure graph tells you </li></ul><ul><ul><li>how many males and females there are in a population </li></ul></ul><ul><ul><li>how many people there are at each age level </li></ul></ul><ul><li>Rapidly growing countries have a wide base because a large percentage of the population is made up of children and teenagers </li></ul><ul><li>A stable population has a fairly equal percentage of people in each age category </li></ul>
  10. 10. Ecology and growth <ul><li>Needs differ throughout the world </li></ul><ul><li>Some = concerned w/ basic needs. Others = concerned about maintaining healthy conditions </li></ul><ul><li>Resources that humans depend on daily </li></ul><ul><ul><li>uncontaminated drinking water (and for agriculture) </li></ul></ul><ul><ul><li>adequate sewage facilities </li></ul></ul><ul><ul><li>ability to provide food </li></ul></ul>
  11. 11. Ecology and growth cont. <ul><li>Resources needed for life (struggling to survive) </li></ul><ul><ul><li>food </li></ul></ul><ul><ul><li>water </li></ul></ul><ul><ul><li>(both can become scarce) </li></ul></ul><ul><li>Other problems = where to properly dispose of waste </li></ul><ul><li>These conditions can lead to stress on current resources and contribute to spread of disease </li></ul>