Estimating Population Sizes (B4)

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  • Estimating Population Sizes (B4)
    • Population
      • All the organisms of one species in a habitat
      • Populations of a different species in a habitat make up a comunity
    • Estimate by scaling up from a small sample area
      • Quadrat
        • Square frame  used to study a small area within frame and scale up findings to make estimates
    • Estimate by using Capture-Recapture
      • 1) Capture a sample of the population + mark the animals in a harmless way
      • 2) Release them back into the environment
      • 3) Recapture another sample of the population. count how many of this sample are marked.
      • 4) Estimate population size by using this equation=
        • Population size= (number in first sample x number in second sample) / number in second sample previously marked
    • Important points about these methods
      • 1) The sample size affects the accuracy of the estimate- bigger sample, the more accurate
      • 2) when using capture-recapture, you have to assume the following things-
        • There have been no changes to population sizes due to deaths, immigration or emigration
        • The marking hasn't affected the chances of survival
        • The sampling methods for the capture and recapture were identical (traps in same place ect)


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