Estimating Population SizeA population is a group of the same species that lives in one area, or habitat, such as all the grasshoppers that live in a field or a meadow. It is often difficult, if not impossible, to determine the population of an organism in itshabitat by direct counts. Therefore, scientists must use other methods to estimate the size of a population.Scientists often sample the population instead. Mark and recapture is a method used by scientists toestimate the population size of mobile organisms. For example, to monitor grasshopper populations, scientists capture and mark grasshoppers with paint and then release them back into the wild. When scientists later repeat the survey, the captured grasshoppers will include marked and unmarked grasshoppers. Scientists calculate the ratio of marked to unmarked animals and use this data to estimate the total population size. This method assumes that all individuals are equally likely to be caught when both surveys are taken.Population desist is the number of individuals of a population in a given unit of living space, such as the number of grasshoppers per square meter. Migratory grasshoppers may live in wild fields near corps. In small population densities, such as 0-3 grasshoppers per square meter, the grasshoppers are not that harmful. If their density increases the amount of damage they are likely to cause to surrounding plants increases. The migratory grasshopper can greatly increase its population from one year to the next. If conditions are right, including a lack of predators, optimal temperature for
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- Fall '19
- Population Ecology, population size