Population Ecology Intro


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chapter 5 population ecology notes

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Population Ecology Intro

  1. 1. Population Ecology
  2. 2. What is population? <ul><li>Group of individuals of the same species that live in the same area </li></ul>
  3. 3. Does population change? <ul><li>Sea otters, kelp, and sea urchins </li></ul>
  4. 4. <ul><li>Kelp forests offer a habitat for sea otters </li></ul><ul><li>Sea urchins feed on kelp </li></ul><ul><li>Sea otters feed on sea urchins </li></ul>
  5. 5. Then come the hunters...
  6. 6. <ul><li>What do you think happens when sea otters are hunted? </li></ul><ul><ul><li>Sea urchins increase or decrease? </li></ul></ul><ul><ul><li>Kelp forest increase or decrease? </li></ul></ul><ul><li>Sea otters are then placed on the endangered species list </li></ul><ul><li>So now what happens to the population of sea otter? </li></ul><ul><ul><li>Starts to increase </li></ul></ul><ul><li>How does this affect the kelp and the sea urchins? </li></ul><ul><ul><li>Sea urchins start to get eaten again=decrease in # </li></ul></ul><ul><ul><li>Kelp increases b/c less sea urchins to eat them </li></ul></ul>
  7. 7. But now we have a new hunter….
  8. 8. What happens to the sea otter, kelp, and sea urchins?
  9. 9. What does this tell us about population? <ul><li>Population changes </li></ul><ul><li>There are many factors that influence a population </li></ul><ul><ul><li>Natural </li></ul></ul><ul><ul><li>Unnatural </li></ul></ul><ul><li>Population density has a great impact on ecosystems </li></ul>
  10. 10. 3 important characteristics of Population <ul><li>Geographic Distribution </li></ul><ul><li>Density </li></ul><ul><li>Growth Rate </li></ul>***Population Age structure is also an important characteristic
  11. 11. Geographic Distribution <ul><li>AKA Range </li></ul><ul><li>Describes an area inhabited by a population </li></ul><ul><li>Can vary </li></ul><ul><ul><li>Few cubic centimeters </li></ul></ul><ul><ul><li>Kilometers of the ocean </li></ul></ul>
  12. 14. Density <ul><li># of individuals per unit area </li></ul><ul><li>Low density </li></ul><ul><ul><li>Cactus in desert </li></ul></ul><ul><li>High density </li></ul><ul><ul><li>Other desert plants and succulents </li></ul></ul>
  13. 16. Math Time <ul><li>Formula for calculating population density </li></ul><ul><li>Population density= Number of individuals </li></ul><ul><li>units area </li></ul><ul><li>Problem : Suppose there are 150 bullfrogs living in a pond that covers an area of 3 square kilometers. What is the density of the bullfrog population? </li></ul><ul><li>50 bullfrogs per square kilometer </li></ul>
  14. 17. Growth Rate <ul><li>Many factors affect growth rate </li></ul>
  15. 18. 3 Factors that affect population size <ul><li># of births </li></ul><ul><li># of deaths </li></ul><ul><li># of individuals that enter or leave population </li></ul>Population will increase or decrease depending on # of individuals added or removed
  16. 19. <ul><li>Have more births than deaths? </li></ul><ul><ul><li>Population increases </li></ul></ul><ul><li>Have more deaths than births? </li></ul><ul><ul><li>Population decreases </li></ul></ul><ul><li>Have equal amounts of births and deaths? </li></ul><ul><ul><li>Population remains constant </li></ul></ul>What happens to the population when we….
  17. 21. Immigration <ul><li>“ im”= in </li></ul><ul><li>Migrate= to move from one place to another </li></ul><ul><li>Immigration is the individual movement into an area </li></ul><ul><li>Animals in search of mates and food in new areas </li></ul>
  18. 26. Emigration <ul><li>“ E”  means ‘out’ </li></ul><ul><li>Migrate  means to move from one place to another </li></ul><ul><li>Emigrate means individuals moving out of one place and into another </li></ul><ul><li>Young wolves and bears leaving as they mature </li></ul><ul><li>Shortage of food </li></ul>
  19. 27. Two types of growth <ul><li>Exponential growth </li></ul><ul><ul><li>Individuals reproduce at a constant rate </li></ul></ul><ul><li>Logistic growth </li></ul><ul><ul><li>Occurs when a populations growth slows or stops after a period of exponential growth </li></ul></ul>
  20. 28. Exponential Growth <ul><li>Occurs under ideal conditions with unlimited resources </li></ul><ul><li>Think about exponents in math…. </li></ul><ul><li>Starts slowly then sky rockets to infinity </li></ul><ul><li>Our graph will look like a J </li></ul><ul><li>Bacteria </li></ul>
  21. 29. Lets look at bacteria… <ul><li>Bacteria reproduce by splitting in half </li></ul><ul><li>Bacteria have a doubling time of 30 minutes </li></ul><ul><li>If you start will one bacterium, how many bacteria will there be after the first 30 minutes? </li></ul><ul><ul><li>2 </li></ul></ul><ul><li>After an hour? </li></ul><ul><ul><li>4 </li></ul></ul><ul><li>After an hour and a half? </li></ul><ul><ul><li>8 </li></ul></ul><ul><li>After two hours? </li></ul><ul><ul><li>16 </li></ul></ul><ul><li>After 15 hours? </li></ul><ul><ul><li>Over a billion </li></ul></ul>
  22. 31. Logistic Growth <ul><li>As resources become less available, the growth of the population slows or stops </li></ul><ul><li>S-shape curve </li></ul><ul><li>What we usually see in nature </li></ul>
  23. 33. Carrying Capacity <ul><li>The largest number of individuals that a given environment can support </li></ul><ul><li>The part of the logistic graph after the exponential growth…the flattening out </li></ul><ul><li>The point at which this flat line reaches the y-axis is the size of the population when the growth rate reaches zero </li></ul><ul><li>This doesn’t mean the population stops growing </li></ul><ul><li>Many factors slow the growth of plants and animals… </li></ul>