Ecology of populations


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Ecology of populations

  1. 1. Ecology of Populations Reference: Chapter 46
  2. 2. Density vs Distribution <ul><li>Density: #/area </li></ul><ul><li>Distribution </li></ul><ul><li>Ecological reasons for each? </li></ul>
  3. 3. Limiting factors <ul><li>Resource or environmental condition that restricts the abundance or distribution of an organism </li></ul><ul><li>Abiotic or biotic </li></ul><ul><li>Why is there a </li></ul><ul><li>tree line? </li></ul>
  4. 4. Intrinsic Rate of Natural Increase <ul><li>What increases population size? </li></ul><ul><li>What decreases population size? </li></ul>
  5. 5. Intrinsic Rate of Natural Increase, r <ul><li>Population growth rate </li></ul><ul><ul><li>+ natality (birth) rate </li></ul></ul><ul><ul><li>- mortality (death) rate </li></ul></ul><ul><ul><li>+ immigration rate </li></ul></ul><ul><ul><li>- emigration rate </li></ul></ul><ul><li>If immigration = emigration </li></ul><ul><ul><li>r = birth rate – death rate </li></ul></ul><ul><li>Rates expressed per capita </li></ul><ul><ul><li>2 out of 50 die = 0.04 death rate </li></ul></ul>
  6. 6. <ul><li>Discrete breeder: one reproductive event in lifetime </li></ul><ul><li>Continuous breeder: many reproductive rates through out lifetime </li></ul>
  7. 7. Exponential Growth <ul><li>Unchecked growth </li></ul><ul><ul><li>Unlimited resources </li></ul></ul><ul><ul><li>Protection from disease & predators </li></ul></ul><ul><li>Biotic potential = MAX growth under ideal conditions </li></ul><ul><li>R = net reproductive rate (offspring that survives from one female) </li></ul>N t+1 = RN t N t = # females present N t+1 = population size the following year
  8. 8. Environmental resistance <ul><li>Populations don’t grow unchecked forever… </li></ul><ul><li>Stopped by … </li></ul>
  9. 9. Logistic Growth <ul><li>Growth slows or stops as resources dwindle </li></ul><ul><li>Carrying capacity </li></ul><ul><ul><li>Maximum # of one species environment can support </li></ul></ul>
  10. 10. Logistic Growth
  11. 11. Life History Patterns <ul><li>Environment may influence reproductive strategies </li></ul><ul><li>Density-independent factors </li></ul><ul><ul><li>Weather, natural disasters, etc. </li></ul></ul><ul><li>Density-dependent factors </li></ul><ul><ul><li>Parasitism, competition, predation </li></ul></ul>
  12. 12. Life History Patterns <ul><li>Unstable environment </li></ul><ul><ul><li>Density-independent factors keep population from getting too high </li></ul></ul><ul><ul><li>r -selection </li></ul></ul><ul><ul><ul><li>Rate of increase is most important </li></ul></ul></ul><ul><ul><li>r -strategists </li></ul></ul><ul><ul><ul><li>Many offspring; minimal parental care </li></ul></ul></ul><ul><ul><ul><li>Small body size; mature quickly </li></ul></ul></ul><ul><ul><ul><li>Good dispersers and colonizers </li></ul></ul></ul><ul><ul><ul><li>Get it while the getting’s good! </li></ul></ul></ul><ul><ul><ul><li>“Live fast, die young” </li></ul></ul></ul>
  13. 13. Life History Patterns <ul><li>Stable environment </li></ul><ul><ul><li>Density-dependent factors keep population from getting too high </li></ul></ul><ul><ul><li>K -selection </li></ul></ul><ul><ul><ul><li>Carrying capacity is most important </li></ul></ul></ul><ul><ul><li>K -strategists </li></ul></ul><ul><ul><ul><li>Few offspring; extensive parental care </li></ul></ul></ul><ul><ul><ul><li>Large body size; mature late </li></ul></ul></ul><ul><ul><ul><li>Specialists </li></ul></ul></ul><ul><ul><ul><li>“Slow and steady wins the race” </li></ul></ul></ul>
  14. 14. <ul><li>Cohort = all the members of population born at the same time. </li></ul><ul><ul><li>Survivorship = probability of newborn individuals of a cohort surviving to particular ages </li></ul></ul>Survivorship Curves
  15. 15. Survivorship Curves
  16. 16. Human Population Growth <ul><li>Human population has an exponential growth pattern. </li></ul><ul><ul><li>Doubling time currently estimated at 53 years. </li></ul></ul><ul><li>Population Size </li></ul><ul><ul><li>1800 1 Billion </li></ul></ul><ul><ul><li>1930 2 Billion </li></ul></ul><ul><ul><li>1960 3 Billion </li></ul></ul><ul><ul><li>2000 6 Billion </li></ul></ul>
  17. 18. World Population Growth
  18. 19. Country Development <ul><li>More-Developed Countries (MDCs) </li></ul><ul><ul><li>Slow population growth. </li></ul></ul><ul><ul><li>High standard of living. </li></ul></ul><ul><ul><li>Completed Demographic Transition. </li></ul></ul><ul><ul><ul><li>North America and Europe </li></ul></ul></ul><ul><li>Less-Developed Countries (LDCs) </li></ul><ul><ul><li>Rapid population growth. </li></ul></ul><ul><ul><li>Low standard of living. </li></ul></ul><ul><ul><ul><li>Latin America </li></ul></ul></ul><ul><ul><ul><li>Africa and Asia </li></ul></ul></ul>
  19. 21. Age Distributions <ul><li>Age Structure Diagrams divide populations into three age groups. </li></ul><ul><ul><li>Pre-Reproductive </li></ul></ul><ul><ul><li>Reproductive </li></ul></ul><ul><ul><li>Post-Reproductive </li></ul></ul>
  20. 22. More-Developed Countries
  21. 23. Less-Developed Countries
  22. 24. Age Structure Diagrams <ul><li>Keep your eye on the reproductive ages! </li></ul>
  23. 25. Environmental Impact <ul><li>Environmental impact of a population is measured in terms of: </li></ul><ul><ul><li>Population Size </li></ul></ul><ul><ul><li>Resource Consumption Per Capita </li></ul></ul><ul><ul><li>Resultant Pollution </li></ul></ul>
  24. 26. Environmental Impact
  25. 27. Echoes of the Boom…
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