Final answer:
The Lincoln Index is a biological method to estimate animal population sizes using the capture-recapture principle and is calculated using the formula N = (n1 x n2) / m.
Step-by-step explanation:
The Lincoln Index is a method used by ecologists to estimate the size of animal populations in a given area. It is based on the capture-recapture principle. The formula to calculate the Lincoln Index is N = (n1 x n2) / m, where N is the estimated total population size, n1 is the number of individuals first captured and marked, n2 is the number captured in the second round, and m is the number of marked individuals recaptured in the second round. By using the Lincoln Index, one assumes there is no change in the population size between the two captures, that markings do not affect the chance of re-capture, and each member of the population has an equal chance of being captured.