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Chapter 8.3 presentation


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Chapter 8.3 presentation

  1. 1. 8.3 Population Ecology 8.3 Population Ecology
  2. 2. <ul><li>A population is defined as a group of organisms of the same species occupying a particular area. </li></ul><ul><li>Population ecology is the study of relationship between : </li></ul><ul><li>(a) different population </li></ul><ul><li>(b) populations and the environment </li></ul><ul><li>Characteristics of a populations : </li></ul><ul><li>(a) population size </li></ul><ul><ul><ul><li>the number of individuals making up the population </li></ul></ul></ul><ul><li>(b) population density </li></ul><ul><ul><ul><li>the number of organisms per unit area or volume of the habitat </li></ul></ul></ul><ul><ul><ul><li>affected by the abiotic factors, biotic factors, birth rate, death rate, immigration and emigration. </li></ul></ul></ul><ul><ul><ul><li>biotic interactions regulate the population growth (competition, predation and parasitism ) </li></ul></ul></ul><ul><li>(c) population distribution </li></ul><ul><ul><ul><li>the general pattern in which the population members are distributed in the habitat </li></ul></ul></ul><ul><li>Direct counting is useful to estimate the size and density of a population </li></ul>
  3. 3. 『 Quadrat Sampling Technique 』 <ul><li>estimate the size of plant populations </li></ul><ul><li>study of the populations of immobile </li></ul><ul><li>animals </li></ul><ul><li>to determine the percentage of the </li></ul><ul><li>types of vegetation and animals </li></ul><ul><li>occurring within the marked area </li></ul>
  4. 4. Quadrat <ul><li>Typically a square or rectangular frame constructed of plastic, metal rod, or wood which forms a square of a known area. </li></ul><ul><li>Strings are used to subdivide the quadrant into smaller squares. </li></ul><ul><li>Size of a quadrat used depends on the size, distribution and density of the organisms being studied </li></ul><ul><li>isolate a sample </li></ul><ul><li>Set up randomly throughout the area being studied </li></ul>
  5. 5. Quadrat Sampling
  6. 6. Quadrat sampling technique can be used to determine : <ul><li>Frequency </li></ul><ul><ul><li>Number of times a particular species is found present when a quadrat is thrown a certain number of times. </li></ul></ul><ul><ul><li>number of quadrats containing the species </li></ul></ul><ul><ul><li>__________________________________ x 100% </li></ul></ul><ul><ul><li>number of quadrats </li></ul></ul>Frequency =
  7. 7. <ul><li>Density </li></ul><ul><li>The mean number of individuals of a species per unit </li></ul><ul><li>area. </li></ul><ul><li>total number of individuals of a </li></ul><ul><li>species in all quadrats </li></ul><ul><li>= ______________________________ x 100% </li></ul><ul><li>number of quadrats x quadrat area </li></ul>Density
  8. 8. <ul><li>Percentage coverage </li></ul><ul><li>An indication of how much area of the </li></ul><ul><li>quadrat is occupied by a species. The </li></ul><ul><li>percentage coverage is useful when it </li></ul><ul><li>is not possible to identify separate </li></ul><ul><li>individuals. </li></ul><ul><li>aerial coverage of all quadrats (m ) </li></ul><ul><li>= ______________________________ x 100% </li></ul><ul><li>number of quadrats x quadrat area </li></ul>2 Percentage coverage 2
  9. 9. Capture, Mark, Release And Recapture Technique
  10. 10. <ul><li>To measure the population sizes of mobile animals in an area </li></ul><ul><li>Initially, a specific animal sample is captured and marked with </li></ul><ul><li>a ring, a tag or with water-proof coloured ink, cellulose paint </li></ul><ul><li>or nail varnish. </li></ul><ul><li>The marked animals are then released into the general population. </li></ul><ul><li>After a duration of a few days to week, a second animal sample is </li></ul><ul><li>captured and the number of marked animals in the second sample is </li></ul><ul><li>counted and recorded. </li></ul><ul><li>Based on the data obtained, the population size of animal in the </li></ul><ul><li>area can be estimated by using the formula below. </li></ul><ul><li>( number of organisms in the first sample) x </li></ul><ul><li>(number of organisms in the second sample) </li></ul><ul><li>____________________________________ </li></ul><ul><li>number of marked organisms required </li></ul>Population size = Capture-recapture Method
  11. 11. Assumptions are made in the capture-recapture method: <ul><li>the marked animals are not harmed or predated upon </li></ul><ul><li>the marked animals mix freely in the population upon their release </li></ul><ul><li>the animal population under </li></ul><ul><li>study is stable with no </li></ul><ul><li>significant changes during </li></ul><ul><li>the investigation (eg. </li></ul><ul><li>mortality because of </li></ul><ul><li>diseases, and immigration </li></ul><ul><li>or emigration of the </li></ul><ul><li>animals does not take </li></ul><ul><li>place) </li></ul><ul><li>each marked individual </li></ul><ul><li>has the same </li></ul><ul><li>probability of being </li></ul><ul><li>recaptured as an </li></ul><ul><li>unmarked individual </li></ul>
  12. 12. To ensure that the results are more accurate : <ul><li>It is necessary to trap or capture relatively </li></ul><ul><li>large samples </li></ul><ul><li>The animals must be captured randomly </li></ul><ul><li>E nough time must be given for the marked </li></ul><ul><li>and unmarked individuals to mix with the </li></ul><ul><li>rest of population </li></ul><ul><li>The marks used must be permanent and </li></ul><ul><li>must not be easily detected by the </li></ul><ul><li>predators or hinder the animals’ movement </li></ul>
  13. 13. <ul><li>Capture-recapture method </li></ul>
  14. 14. <ul><li>Capture- </li></ul><ul><li>recapture </li></ul><ul><li>method </li></ul>
  15. 15. Random Sampling
  16. 16. Random Sampling Method <ul><li>To obtain a number of records </li></ul><ul><li>from different positions within </li></ul><ul><li>a defined habitat </li></ul><ul><li>The entire area to be studied is </li></ul><ul><li>divided into identical units </li></ul><ul><li>A quadrat can be thrown at </li></ul><ul><li>the field studied in a random </li></ul><ul><li>manner and the number of </li></ul><ul><li>individuals within the quadrat </li></ul><ul><li>can be counted </li></ul>Estimated total = population Number of individuals recorded total number of units ____________________ x number of units sampled
  17. 17. <ul><li>Random Sampling Method </li></ul>
  18. 18. Removal method
  19. 19. Removal method <ul><li>The removal method of estimating populations has been widely used in studies of small mammals. The method involves the removal of individuals from the popula­tion either permanently or for the duration of the study. </li></ul><ul><li>The basis of these methods is the expectation that the number caught and removed from the population at a given time of trapping will be greater than the number caught at later trapping using the same sampling effort. </li></ul><ul><li>That is, as one reduces the population size, the size of the catch will decrease. </li></ul><ul><li>Necessary assumptions of removal methods are listed below. </li></ul><ul><li>1. The sampling must be </li></ul><ul><li>random. </li></ul><ul><li>2. Except for the effects of </li></ul><ul><li>the trapping, the </li></ul><ul><li>population is not increasing </li></ul><ul><li>or decreasing in size </li></ul><ul><li>(through the combined </li></ul><ul><li>effects of births, deaths, </li></ul><ul><li>immigration, and emigration). </li></ul><ul><li>3. The probability of capturing an </li></ul><ul><li>individual is the same for each </li></ul><ul><li>period of sampling. </li></ul>
  20. 20. Abiotic factors which influence the population distribution of an organism
  21. 21. <ul><li>The population distribution of an organism is </li></ul><ul><li>affected by changes in the abiotic factors such </li></ul><ul><li>as : </li></ul><ul><li>a) temperature </li></ul><ul><li>b) light intensity </li></ul><ul><li>c) humidity </li></ul><ul><li>d) pH </li></ul><ul><li>e) aspect </li></ul><ul><li>Changes in these abiotic components influence </li></ul><ul><li>the population distribution of an organism. </li></ul>
  22. 22. THE END <ul><li>Prepared by Group 007 </li></ul>