In this exercise you will estimate the number of white beans (black-eyed peas) in a container by a modification of the "mark, release, recapture" method used by field ecologists to estimate the size of an animal population in an ecosystem.

1. Remove 100 white beans and substitute 100 red beans (small red chili beans). This process will simulate the "marking" of 100 individuals from the population.
2. Mix the beans to distribute the marked individuals in the population. (Handle the beans gently. The black-eyed peas have a tendency to crumble when roughly handled.)
3. Withdraw a sample of the bean population and count the numbers of each type of bean in the sample. Be sure to record your results before returning the sample to the population.
4. Estimate the number of beans in the population using the following formula:

PTotal = (S_Total)(P_Marked)/(S_Marked)

P_Marked = Number red beans substituted in population.
P_Total = Total number of beans (red and white) in population.
S_Marked = Number of red beans in sample.
S_Total = Total number of beans (red and white) in sample.

5. Return the sample to the population and mix well again. Repeat this sampling process for a total of 5 times.
6. Look at your five estimates of population size. How well do they agree? Calculate the range and mean (average) for your estimates.
7. Now count the population (total number of beans, both red and white) to see how close your estimates were to the actual population.

Data Sheet: Mark, Release, Recapture

Estimates of P_TOTAL

Range: ___________________________

Average: ___________________________

Actual Count of P_TOTAL

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