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Chapter 8.3 presentation
Chapter 8.3 presentation
Chapter 8.3 presentation
Chapter 8.3 presentation
Chapter 8.3 presentation
Chapter 8.3 presentation
Chapter 8.3 presentation
Chapter 8.3 presentation
Chapter 8.3 presentation
Chapter 8.3 presentation
Chapter 8.3 presentation
Chapter 8.3 presentation
Chapter 8.3 presentation
Chapter 8.3 presentation
Chapter 8.3 presentation
Chapter 8.3 presentation
Chapter 8.3 presentation
Chapter 8.3 presentation
Chapter 8.3 presentation
Chapter 8.3 presentation
Chapter 8.3 presentation
Chapter 8.3 presentation
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Chapter 8.3 presentation

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  • 1. 8.3 Population Ecology 8.3 Population Ecology
  • 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. 『 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. 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. Quadrat Sampling
  • 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. <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. <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. Capture, Mark, Release And Recapture Technique
  • 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. 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. 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. <ul><li>Capture-recapture method </li></ul>
  • 14. <ul><li>Capture- </li></ul><ul><li>recapture </li></ul><ul><li>method </li></ul>
  • 15. Random Sampling
  • 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. <ul><li>Random Sampling Method </li></ul>
  • 18. Removal method
  • 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. Abiotic factors which influence the population distribution of an organism
  • 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. THE END <ul><li>Prepared by Group 007 </li></ul>

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