1. Animal marker recapture method

Mark recapture method refers to capture some individuals in the living environment of the investigated population, mark these individuals and put them back in the original environment, and then capture them after a period of time, and estimate the population according to the proportion of marked individuals in the total capture. It is often used for sampling survey of animal population density, and the calculation formula is: the total number of individuals in the population/the total number of recaptured individuals = the total number of individuals who have started to mark/the total number of individuals who have been recaptured with markers.

Example 1 When investigating the crucian carp population in the pond, 200 crucian carp were captured for the first time, all of which were marked and released. After a while, 160 crucian carp were caught for the second time, among which 10 crucian carp was marked, so the total number of crucian carp in the pond was about.

Research and analysis: the marked recapture method is often used to count the number of individuals in an animal population, and its calculation formula is: the total number of individuals in the population/the total number of recaptured individuals = the total number of individuals who started to mark/the total number of individuals with marks in recaptured individuals, so the number of individuals in the population is x∶ 160= 200∶ 10, and x=3200. Answer: 3200 tails. 2. Plant-like methods

The sampling method is to randomly select several quadrats in the living environment of the investigated population, calculate the population density of each quadrat by counting the number of individuals in each quadrat, and take the average population density of all quadrats as the population density. It is often used for sampling survey of plant population density. The shapes of quadrats can be varied, but the selection of quadrats must be widely representative, which can be guaranteed by random sampling.

Example 2 A student counts a plant by sampling. Figure 3- 1- 1 shows the distribution of the plant in one of the quadrats (note: the black dots in the figure indicate the plant). When calculating the plants in the quadrat, the number to be recorded is. Research and analysis: When counting by sample method, if there are newly growing plants on the boundary line, only the individuals on the adjacent sides of the sample are counted. Answer: 8.