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Human Population Dynamics


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Human Population Dynamics

  1. 1. Population Dynamics Chapter 9 Chapter 12 Chapter 13
  2. 2. Describing Populations <ul><li>A population is defined as a group of organisms of the same species. </li></ul><ul><li>- inhabit a defined geographic area at the same time </li></ul><ul><li>- generally rely on each other </li></ul><ul><li>- rely on the same resources </li></ul><ul><li>- influenced by the same environmental factors </li></ul>
  3. 3. Characteristics of Populations <ul><li>Population Density- refers to the number of individuals that inhabit a certain unit of land or water area. </li></ul><ul><li>EX: Number of squirrels in a particular </li></ul><ul><li>forest. </li></ul>
  4. 4. Characteristics of Populations <ul><li>Population Dispersion – refers to how individuals are spaced within a region. </li></ul><ul><li>3 main ways : </li></ul><ul><li>Random - position of each individual is not influenced by other members of their population- rare- EX: plants in a field </li></ul><ul><li>Clumping- individuals “flock” together- most common- EX: Fish school to avoid predation </li></ul><ul><li>Uniform- members are uniformly spaced- </li></ul><ul><li>EX: Trees in a forest- often results from competition for resources. </li></ul>
  5. 5. Population Growth <ul><li>Biotic Potential- the amount a population would grow if there were unlimited resources- not a practical model because organisms are limited in nature by amount of food, space, light, air, water, etc… </li></ul><ul><li>The intrinsic rate of increase ( r ) is the rate at which a population would grow if it had unlimited resources. </li></ul><ul><li>No population can increase its size indefinitely. </li></ul>
  6. 6. Population Growth <ul><li>Carrying Capacity (K)- defined as the maximum population size that can be supported by the available resources of the region. </li></ul><ul><li>Different geographic regions have different carrying capacities for populations of different species because different species have different requirements for life. </li></ul><ul><li>EX: Bacteria vs. Zebras </li></ul>
  7. 7. Population Growth <ul><li>Populations grow rapidly with ample resources, but as resources become limited, its growth rate slows and levels off. </li></ul>
  8. 8. Population Growth <ul><li>As a population levels off, it often fluctuates slightly above and below the carrying capacity. </li></ul><ul><li>Reproductive Lag- </li></ul>
  9. 9. A: Represents the biotic potential of the species B: Shows how the population overshoots the carrying capacity C: Represents the logistic growth D: Represents linear growth E: Carrying capacity- the maximum number of individuals that can be supported by a particular ecosystem.
  10. 10. Population Growth- Stretching Carrying Capacity <ul><li>Adapt: Over time species may increase their carrying capacity by developing adaptations. </li></ul><ul><li>Move: Some species maintain their carrying capacity by migrating to other areas. </li></ul><ul><li>Switch Habits: So far, technological, social, and other cultural changes have extended the earth’s carrying capacity for humans. </li></ul>
  11. 11. Rule of 70’s <ul><li>Predicting long-term population growth- </li></ul><ul><li>70/ growth rate = doubling time (daily) </li></ul><ul><li>72/ growth rate = doubling time (years) </li></ul><ul><li>If a population of a country grows at a rate of 5% a year, the number of years required for the pop to double is what? </li></ul>
  12. 12. Population Growth- Reproductive Strategies <ul><li>R- selected species- reproduce early in life and often- high capacity for reproduction- little care is given to the offspring- high numbers </li></ul><ul><li>EX: Bacteria, Insects, Algae </li></ul>
  13. 13. Many small offspring Little or no parental care and protection of offspring Early reproductive age Most offspring die before reaching reproductive age Small adults Adapted to unstable climate and environmental conditions High population growth rate (r) Population size fluctuates wildly above and below carrying capacity (K) Generalist niche Low ability to compete Early successional species r-Selected Species
  14. 14. Population Growth- Reproductive Strategies <ul><li>K- Selected Species- reproduce later in life, produce fewer offspring, and devote a significant amount of time and energy to the nurturing of their offspring. </li></ul><ul><li>EX: Humans, lions, cows </li></ul>
  15. 15. Fewer, larger offspring High parental care and protection of offspring Later reproductive age Most offspring survive to reproductive age Larger adults Adapted to stable climate and environmental conditions Lower population growth rate (r) Population size fairly stable and usually close to carrying capacity (K) Specialist niche High ability to compete Late successional species K-Selected Species
  16. 16. Population Growth- Reproductive Strategies <ul><li>R-selected species tend to be opportunists while K-selected species tend to be competitors . </li></ul>
  17. 17. Population Cycles <ul><li>Boom and Bust Cycle- common among r-strategists- rapid increase in population growth and then equally rapid drop off. </li></ul><ul><li>These rapid changes are linked to changes in the environment. When conditions are good- population increases rapidly. </li></ul><ul><li>EX: Summer vs. Winter </li></ul>
  18. 18. Population Cycles <ul><li>Predator-Prey Cycle- one population follows the other’s rise and decline. </li></ul><ul><li>This relationship explains why many endangered species are large carnivores. Humans alter the environment killing the prey of many large species. Large species starves and cannot reproduce. </li></ul>
  19. 19. Predator- Prey Cycles
  20. 20. Survivorship Curves <ul><li>The populations of different species vary in how long individual members typically live. </li></ul>
  21. 21. Factors Influencing Population Growth <ul><li>Density Dependent Factors- factors that are a result of the population size </li></ul><ul><li>Birth and Death rates </li></ul><ul><li>Increased predation </li></ul><ul><li>Competition for food, space or water </li></ul><ul><li>Disease </li></ul><ul><li>Build-up of toxic materials (biomagnification) </li></ul>
  22. 22. Factors Influencing Population Growth <ul><li>Density Independent Factors- factors that limit population size regardless of the number of individuals. </li></ul><ul><li>Fires </li></ul><ul><li>Storms </li></ul><ul><li>Volcanic Activity </li></ul><ul><li>Floods </li></ul><ul><li>Earthquakes </li></ul>
  23. 23. Human Populations <ul><li>Demography - </li></ul><ul><li>The study of human populations, their characteristics and changes. </li></ul>
  24. 24. Human Populations <ul><li>How do population numbers change? </li></ul><ul><li>Emigration- movement of people out of a country </li></ul><ul><li>Immigration- movement of people into a country </li></ul><ul><li>Birth rate </li></ul><ul><li>Death rate </li></ul>
  25. 25. Human Populations <ul><li>The human population has been growing exponentially for three centuries. </li></ul><ul><li>The most significant additions to human populations are due to births. </li></ul><ul><ul><li>Total fertility rate (TFR) : the average number of children a woman has during her reproductive years. </li></ul></ul><ul><ul><li>Replacement-level fertility : the number of children a couple must bear to replace themselves. </li></ul></ul>
  26. 26. Human Populations <ul><li>Declining Fertility Rates </li></ul><ul><li>The average number of children that a woman bears has dropped sharply. </li></ul><ul><li>This decline is not low enough to stabilize the world’s population in the near future. </li></ul>
  27. 27. Human Populations <ul><li>Nearly 2.9 million people were added to the U.S. in 2006: </li></ul><ul><ul><li>59% occurred because of births outnumbering deaths. </li></ul></ul><ul><ul><li>41% came from illegal and legal immigration. </li></ul></ul>
  28. 28. Human Populations- U.S. <ul><li>The baby bust that followed the baby boom was largely due to delayed marriage, contraception, and abortion. </li></ul>
  29. 29. Fig. 9-7, p. 176 47 years Homicides per 100,000 people Hourly manufacturing job wage (adjusted for inflation) Living in suburbs Homes with electricity Homes with flush toilets High school graduates Married women working outside the home Life expectancy 1.2 5.8 $15 $3 52% 10% 99% 2% 98% 10% 83% 15% 81% 2000 1900 8% 77 years
  30. 30. World Population Growth <ul><li>Factors Influencing Total Fertility Rates : </li></ul><ul><li>The availability of birth control and abortions. </li></ul><ul><li>Education level of women. </li></ul><ul><li>The populations religious beliefs, customs, culture and traditions. </li></ul><ul><li>The demand for children in the work force. </li></ul><ul><li>The existence of retirement systems- pensions. </li></ul><ul><li>Marriage age. </li></ul><ul><li>Urbanization. </li></ul>
  31. 31. World Population Growth <ul><li>Population growth is considerably higher because the death rate has dropped. </li></ul><ul><li>People live longer & lower infant mortality rates exist. </li></ul><ul><li>Due to: </li></ul><ul><li>1. Industrial Revolution- improved standards of living. </li></ul><ul><li>2. Clean water sources. </li></ul><ul><li>Better sanitation. </li></ul><ul><li>Dependable food supplies. </li></ul><ul><li>Better health care. </li></ul>
  32. 32. Fig. 9-3, p. 174 Average crude death rate Average crude birth rate World 21 9 All developed countries 11 10 All developing countries 27 8 9 23 Developing countries (w/o China)
  33. 33. Fig. 9-3, p. 174 14 Europe North America United States Oceania Asia Africa Latin and Central America 38 15 21 6 20 7 17 7 14 8 8 11 10
  34. 34. U.S. Population <ul><li>U.S. infant mortality is higher than it could be (ranked 46 th world-wide) due to: </li></ul><ul><ul><li>Inadequate pre- and post-natal care for poor. </li></ul></ul><ul><ul><li>Drug addiction. </li></ul></ul><ul><ul><li>High teenage birth rate. </li></ul></ul>
  35. 35. U.S. Population <ul><li>Since 1820, the U.S. has admitted almost twice as many immigrants and refugees as all other countries combined. </li></ul>
  36. 36. Population Age Structure <ul><li>A population’s growth is dependent upon the number of people In young, middle, and older age groups. </li></ul><ul><li># of people younger than age 15 = </li></ul><ul><li>the major factor determining a country’s population growth. </li></ul><ul><li>Populations with a large proportion of its people in the pre-reproductive ages 1-14 have a large potential for rapid population growth. </li></ul>
  37. 37. Age- Structure Pyramids
  38. 38. <ul><li>32% of the people in developing countries were under 15 years old in 2006 versus only 17% in developed countries . </li></ul>
  39. 39. Reading Population Histograms Birth rate exceeds the death rate. Population is getting larger. Pyramid shaped histogram. EX: Kenya, Nigeria and Saudi Arabia.
  40. 40. Reading Population Histograms Birth rate almost equals death rate. The population is not getting any larger or is growing very slowly. Histogram shape is straighter and more box-like until about age 45-85. EX. US, Australia & Canada has slow growth. Denmark, Austria and Italy has stable growth.
  41. 41. Reading Population Histograms When the birth rate is smaller than the death rate. The pyramid bulges near the top or is inverted . EX: Germany, Bulgaria & Hungary
  42. 42. The Demographic Transitional Model <ul><li>Used to predict population trends based on birth and death rates. </li></ul><ul><li>4 states populations transition between: </li></ul><ul><li>Pre-Industrial State </li></ul><ul><li>Transitional State </li></ul><ul><li>Industrial State </li></ul><ul><li>Post-Industrial State </li></ul>
  43. 43. Pre- Industrial State <ul><li>Slow rate of growth </li></ul><ul><li>High death rate </li></ul><ul><li>High birth rate </li></ul><ul><li>Harsh living conditions ( environmental resistance) </li></ul>
  44. 44. Transitional State <ul><li>Birth rate is high </li></ul><ul><li>Better food, water, and health care </li></ul><ul><li>Death rate is low </li></ul><ul><li>Rapid population growth </li></ul><ul><ul><li>industrialization begins, death rates drops and birth rates remain high. </li></ul></ul>
  45. 45. Industrial State <ul><li>Population growth is slow </li></ul><ul><li>Birth rate drops </li></ul><ul><li>Death rate is similar to the birth rate </li></ul><ul><li>This is because of: </li></ul><ul><ul><li>better access to birth control </li></ul></ul><ul><ul><li>decline in the infant mortality rate </li></ul></ul><ul><ul><li>increased job opportunities for women </li></ul></ul><ul><ul><li>the high cost of raising children who don’t enter the work force until after high school or college </li></ul></ul>
  46. 46. Post-Industrial State <ul><li>Population approaches zero growth rate. </li></ul><ul><li>Then, the birth rate falls below the death rate and the total population size slowly decreases. </li></ul><ul><li>37 countries have reached this stage. (mainly in W. Europe) </li></ul><ul><li>To most population experts, the challenge is to help the remaining 88% of the world to get to this stage. </li></ul>
  47. 47. The Demographic Transition Model
  48. 48. Calculating Population Growth <ul><li>(Birth rate-death rate) + (immigration -emigration) / 10 </li></ul><ul><li>If a population of 10,000 experiences 100 births, 40 deaths, 10 immigrants and 30 emigrants in a year, what is the net annual percentage growth rate? </li></ul>
  49. 49. Developing Countries <ul><li>China is the largest but has taken drastic population control methods. </li></ul><ul><li>By 2050, India is predicted to pass it. Pakistan is projected to become 3 rd with Iran and Ethiopia following. </li></ul><ul><li>However, Russia is losing 600,000 people a year, after being the 4 th largest country in 1950. This is because of environmental pollution, hyperinflation, crime, corruption, disease and despair. </li></ul>
  50. 50. Slowing Population Growth in India and China <ul><li>For more than five decades, India has tried to control its population growth with only modest success. </li></ul><ul><li>Since 1970, China has used a government-enforced program to cut its birth rate in half and sharply reduce its fertility rate. </li></ul>
  51. 51. India’s Failed Family Planning Program <ul><li>Poor planning. </li></ul><ul><li>Bureaucratic inefficiency. </li></ul><ul><li>Low status of women. </li></ul><ul><li>Extreme poverty. </li></ul><ul><li>Lack of administrative financial support. </li></ul><ul><li>Disagreement over the best ways to slow population growth. </li></ul>
  52. 52. India- The Ganges River
  53. 55. China’s Family Planning Program <ul><li>Currently, China’s TFR is 1.6 children per women. </li></ul><ul><li>China has moved 300 million people out of poverty. </li></ul><ul><li>Problems: </li></ul><ul><ul><li>Strong male preference leads to gender imbalance. </li></ul></ul><ul><ul><li>Average population age is increasing. </li></ul></ul><ul><ul><li>Not enough resource to support population. </li></ul></ul>
  54. 56. China <ul><li>In China couples who pledge to have no more than one child receive: </li></ul><ul><li>Extra food </li></ul><ul><li>Larger pensions </li></ul><ul><li>Better housing </li></ul><ul><li>Free medical care </li></ul><ul><li>Salary bonuses </li></ul><ul><li>Free school tuition for their one child </li></ul><ul><li>Preferential treatment in employment when their child enters the job market. </li></ul>
  55. 57. China <ul><li>However, according to some studies, there is a strong preference for male children. </li></ul><ul><li>Girls are aborted at a higher rate than boys </li></ul><ul><li>Some infant girls are killed </li></ul><ul><li>Male children sometimes are fed better than female children. </li></ul>
  56. 58. Fig. 9-15, p. 186 Total fertility rate Percentage of world population Population Population (2050) (estimated) Illiteracy (% of adults) Population under age 15 (%) Population growth rate (%) 17% 20% 1.1 billion 1.3 billion 1.6 billion India China GDP PPP per capita Percentage living below $2 per day Life expectancy 47% 17% 36% 20% 1.6% 0.6% 1.4 billion $5,890 $3,120 47 80 70 years 62 years 27 58 1.6 children per women (down from 5.7 in 1972) Infant mortality rate 2.9 children per women (down from 5.3 in 1970)
  57. 59. Factors Influencing Population Size <ul><li>Family planning has been a major factor in reducing the number of births and abortions throughout most of the world. </li></ul><ul><li>Women tend to have fewer children if they are: </li></ul><ul><ul><li>Educated. </li></ul></ul><ul><ul><li>Hold a paying job outside the home. </li></ul></ul><ul><ul><li>Do not have their human right suppressed. </li></ul></ul>
  58. 60. Factors Influencing Population Size <ul><li>The best way to slow population growth is a combination of: </li></ul><ul><ul><li>Investing in family planning. </li></ul></ul><ul><ul><li>Reducing poverty. </li></ul></ul><ul><ul><li>Elevating the status of women. </li></ul></ul>
  59. 61. Food and Hunger <ul><li>840 million people are hungry </li></ul><ul><li>799 million of those are in developing countries </li></ul><ul><li>The other 40 million are in developed countries </li></ul><ul><li>½ of the US population relies on food stamps </li></ul>
  60. 62. Food and Hunger <ul><li>1.2 billion are overweight </li></ul><ul><li>30% of the U.S. population is obese </li></ul><ul><li>Why does this dichotomy exist? </li></ul><ul><li>POVERTY </li></ul>
  61. 63. Poverty in Developing Nations <ul><li>Trade imbalances exist between developed nations and developing nations. </li></ul><ul><li>U.S. has outsourced production to these poverty-stricken nations. </li></ul><ul><li>Many will work under terrible conditions and long hours because it is a better alternative to continued poverty. </li></ul>
  62. 64. Cage People of Hong Kong
  63. 67. FAIR TRADE <ul><li>www. / watch ?v =NZpUwCfINh8 </li></ul>
  64. 68. Ecological Footprints <ul><li>Environmental Impact Equation (Paul Ehrlich Formula) </li></ul><ul><li>I = P x A x T </li></ul><ul><li>I= Total Impact </li></ul><ul><li>P= Population size </li></ul><ul><li>A= Affluence </li></ul><ul><li>T= Level of tecnology </li></ul>
  65. 69. Ecological Footprints <ul><li>The amount of the earth’s surface that’s necessary to supply the needs of, dispose of the wastes of a particular population. </li></ul><ul><li>U.S. requires 9.7 hectacres/ person </li></ul><ul><li>Indonesia requires 1.1 hectacres/ person </li></ul>
  66. 70. EcoTopia <ul><li>Boulder, Colorado </li></ul><ul><ul><li>Provide bike trails throughout the city </li></ul></ul><ul><ul><li>Citizens voted to increase their taxes to pay for community use green space </li></ul></ul><ul><ul><li>Busses are available to commute throughout the urban sprawl </li></ul></ul><ul><ul><li>Carpools are encouraged </li></ul></ul><ul><ul><li>Strong recycling programs </li></ul></ul>