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Population Estimation Lab

Population Estimation Lab. How do you estimate the size of a population?. Introduction. Measure of population density is essential to many ecological investigations Counting of every individual may not be possible, let alone practical.

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Population Estimation Lab

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  1. Population Estimation Lab How do you estimate the size of a population?

  2. Introduction • Measure of population density is essential to many ecological investigations • Counting of every individual may not be possible, let alone practical

  3. How would you go about estimating the size of a forest community? • Transect Line Study - Locate and run transects - Collect data at each sample point - Interpret data

  4. How would you go about estimating the size and of a forest community? http://www1.esc.edu/personalstaff/kwatson/fieldwork_site/tree_transects.htm

  5. How would you go about estimating the size of an understory community? • Quadrants - Lay down a 1 meter squared quad or a hula hoop - Identify and count everything in the quad

  6. How would you go about estimating the size of an understory community? http://www.science.oregonstate.edu/bpp/faculty/wilson/WorkersQuad_PR%20(2).jpg

  7. How would you go about estimating the size of an animal population? • Live Trapping - Lay out transects - Place traps about 10 meters apart using several transect lines typically at dusk - Check traps at dawn - Mark captured animals - Reset the traps and repeat for several days

  8. How would you go about estimating the size of an animal population? http://www.stolaf.edu/depts/environmental-studies/courses/es-399%20home/es-399-05/Projects/Jared's%20Senior%20Seminar%20Research%20Page/htt.htm

  9. What do you do with the data? Lincoln-Peterson Index • Sample of population (size N) is taken • Animals are marked (m) and released back into the population • Proportion of population is now marked (m/N)

  10. What do you do with the data? • Second sample is (size n) is taken later presumably some of the them are already marked (r) • Proportion of trapped individuals that are marked (recaptured) in second sample (r/n) is crucial to estimating population size

  11. What do you do with the data? Lincoln-Peterson Index Let N= number of animals in the population m= number of animals marked in the first sample and released m/N= proportion of marked animals in the population r= number of recaptured animals in the second sample n= total number of individuals in the second sample Then r/n= proportion of the marked animals in the second sample

  12. What do you do with the data? If the sampling is unbiased, then r/n=m/N. To estimate N, rearrange the above equation to yield N=m*n/r

  13. What assumptions are made with this method? • Sampling is random. Every individual must have an equal probability of capture. • The marked animals must be mixed thoroughly and randomly into the population so that the second sample will accurately reflect the population. • The population size must not change between the two samples.

  14. Mark-Recapture Lab • Estimate the size of a bean population through the mark-recapture method and Lincoln-Peterson Index • Mark the beans by replacing the captured white-colored beans with dark-colored beans • Repeat the lab using a larger sampler (beaker) • Remember to resort your beans at the end!

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