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- 1. Chapter 5 Populations
- 2. Location of the ecosystem – Aleutian Islands, Alaska
- 3. Change in sea otter populations around the Aleutian Islands
- 4. WHY? With your group, discuss as many reason that you can think of that might be causing the sea otter population decline
- 6. Change in sea otter populations around the Aleutian Islands
- 9. Killer whale prey in the Aleutians
- 10. If you were a killer whale… <ul><li>With your partners, rank the order of the three prey species that you would prefer to eat. Give a reasoning for your ranking. </li></ul>
- 16. So who cares if the otters go extinct? <ul><li>With your partners, make a prediction about what will happen to the kelp forests of the Aleutian Islands habitat if the sea otters become extinct </li></ul>
- 20. What’s next? <ul><li>With your partners, sum everything up. What will eventually happen to all the members of this ecosystem if the sea otters become extinct? </li></ul>
- 21. 5 – 1 How Populations Grow <ul><li>What characteristics are used to describe a population? </li></ul><ul><li>What factors affect population size? </li></ul><ul><li>What are exponential growth and logistic growth? </li></ul>
- 22. Characteristics of Populations <ul><li>Three important characteristics of a population are: </li></ul><ul><li>1. geographic distribution – The area inhabited by a population </li></ul><ul><li>2. density - # of individuals per unit area </li></ul><ul><li>3. growth rate – how fast the population grows </li></ul>
- 23. Population Growth <ul><li>Three factors can affect population size: </li></ul><ul><li>1. The # of births </li></ul><ul><li>2. The # of deaths </li></ul><ul><li>3. How fast the population numbers grow </li></ul>
- 24. Exponential Growth <ul><li>Under ideal conditions with unlimited resources, a population will grow exponentially </li></ul><ul><li>When the individuals in a population reproduce at a constant rate </li></ul>
- 25. Exponential Growth
- 26. Logistic Growth <ul><li>Obviously, the conditions for exponential growth are rarely ever met </li></ul><ul><li>As resources become less available, the growth of a population slows or stops </li></ul>
- 27. Logistic Growth <ul><li>Occurs when a population’s growth slows or stops following a period of exponential growth </li></ul><ul><li>Q: Why does this happen? </li></ul><ul><li>A: Lack of resources, lace of space </li></ul>
- 29. Carrying Capacity <ul><li>The largest number of individuals that a population can support </li></ul><ul><li>Q: What is the growth rate when a population is at carrying </li></ul><ul><li>A: Zero </li></ul>
- 30. 5 – 2 Limits to Growth <ul><li>What factors limit population growth? </li></ul>
- 31. Limiting Factor <ul><li>A factor that causes population growth to decrease </li></ul><ul><li>Ex.) Parasitism, disease, drought, extreme weather </li></ul><ul><li>A resource base that is limited can also affect the long term survival of a species </li></ul>
- 32. Density – dependent Factors <ul><li>Limiting factors that depend on population size </li></ul><ul><li>Density dependent factors become limiting only when the population density reaches a certain level </li></ul><ul><li>These factors operate most strongly when a population is large and dense </li></ul><ul><li>Density dependent factors include: </li></ul>
- 33. Competition
- 34. Predation
- 35. Parasitism
- 36. Disease
- 38. Density – Independent Factors <ul><li>Affect all populations in similar ways regardless of the population </li></ul><ul><li>Ex.) unusual weather, natural disasters, seasonal cycles, human activities </li></ul>
- 39. Unusual Weather
- 40. Natural Disasters
- 41. Seasonal Cycles
- 42. Human Activities
- 43. Human Activities
- 44. Density – Independent Factors <ul><li>In response to such factors, many species show a characteristic crash in population size </li></ul><ul><li>Environments are always changing, and most populations can adapt to a certain amount of change </li></ul><ul><li>Populations often grow and shrink in response to such changes </li></ul><ul><li>Major upsets in an ecosystem can lead to long term declines in certain populations </li></ul>
- 45. 5 -3 Human Population Growth <ul><li>How has the size of the human population changed over time? </li></ul><ul><li>Why do population growth rates differ in countries throughout the world? </li></ul>
- 46. Historical Overview <ul><li>Like the populations of many other living organisms, the size of the human population tends to increase with time </li></ul><ul><li>In the U.S. and other developed countries, the current growth is low </li></ul><ul><li>In some developing countries, the human population is growing at a rate of 3 people per. second </li></ul><ul><li>The human population is well on its way to reaching 9 billion in your lifetime </li></ul>
- 48. Exponential Human Growth <ul><li>The following factors have caused a rapid increase in population growth: </li></ul>
- 49. Agriculture
- 50. Industry
- 51. Reliable food source
- 52. Shipping
- 53. Improved sanitation
- 54. Medicine
- 55. Technology
- 56. Patterns of Population Growth <ul><li>Q: Why can’t the human population keep growing exponentially forever? </li></ul><ul><li>A: The resources on earth are limited </li></ul>
- 57. Demography <ul><li>The scientific study of human population </li></ul><ul><li>Birthrates, death rates, and age structure of a population help to protect why some countries have a high growth rate while others grow more slowly </li></ul>
- 58. The Demographic Transition
- 59. Age Structure <ul><li>Population growth depends, in part on how many people of different ages make up a given population </li></ul>
- 60. age-structure diagrams <ul><li>(population profile) – show the population of a country broken down by gender and age group </li></ul>
- 64. 9,078,850,714 .43 2050 8,646,671,023 .54 2040 8,127,227,506 .68 2030 7,515,218,898 .87 2020 6,812,009,338 1.06 2010 6,078,684,329 1.23 2000 5,275,407,789 1.58 1990 4,454,607,332 1.69 1980 3,708,067,105 2.07 1970 3,206,072,286 2.19 1963 3,136,556,092 2.19 1962 3,039,669,330 1.33 1960 2,555,360,972 1.47 1950 Population Average Annual Growth Rate (%) Year World Population: 1950 - 2050

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