09+Lincoln+Index

How do scientist estimate the population of the Beluga whale?

What are the various scientific methods that we can use to estimate the number of individuals in a population?

We will study one of the method today which is called the mark/ recapture method.

The mark/recapture method depends on catching a number of individuals from a population, marking them in some way (e.g. with coloured leg bands for birds) and releasing them. Then a second portion of the population is captured. The whole populations size can be estimated by the formula:
 * P = N x M/R**

//where P = estimated population size// //M = number of individuals marked during first capture// //N = total number of individuals (marked and unmarked) captured second time// //R = number of marked individuals captured second time//

This estimate of population size is called the Lincoln Index.
 * 1) There are some assumptions behind this equation. What do you think are some of the assumptions?
 * 2) There are also a number of technical difficulties involved in this method of estimating population sizes. What are they?

//PAUSE! Lets talk share this in class.//

__**PRACTICE TIME**__ Find a partner to carry out the experiment below.


 * Materials:**
 * 1) Two different coloured beans
 * 2) bag


 * Procedure**:
 * 1) Collect a fistful of yellow beans in any manner you like e.g. grab some without looking.
 * 2) Count all of these beans and put them aside.
 * 3) Replace the yellow beans taken with an identical number of black beans. These different coloured beans represent the “marked” population.
 * 4) To simulate homogeneous mixing of marked and unmarked organisms, shake the container until all the beans are thoroughly mixed.
 * 5) Now collect a fistful of second sample without looking into the container. Count as required.
 * 6) Calculate the population size using the formula given above. How close is it to the actual number of beans you have in your container?
 * 7) Tabulate your result as individual pair and as a class. Is the individual pair result closer to the population size or the total class result?
 * 8) Upload you class data here for all.


 * Results:**

media type="googlespreadsheet" key="tmWok5h6AYh7EICLU1-_Onw" height="480" width="640"


 * Analysis of data:**
 * 1) Study the data from all groups and your group. Did the Lincoln index estimation of the population from most group an over estimation or under estimation of the actual population?
 * 2) Is there any correlation between the size of the initial marked sample and the accuracy of the estimation of the population size?
 * 3) What is the percentage of error for most groups?
 * 4) Is there any group's result that you will not include in your group collation? Why?
 * 5) Why was teh total of all the groups taken instead of the average?


 * Discussion**:
 * 1) Suggest ways to improve on this simulation.
 * 2) Name as many different marked methods as you can.
 * 3) Identify two field conditions under which this method would not be reliable.

Learn more about the method and Lincoln Index [|HERE].