Populaatiokoko

Populaatiokoko (Finnish for population size) refers to the number of individuals comprising a defined population at a given time. In ecology and demography, it is a central measure of abundance and is commonly denoted by N. The term N_e, or effective population size, is used in genetics to describe the number of individuals contributing to the next generation, which can differ from the census size.

Measuring populaatiokoko relies on various methods depending on the population and setting. Censuses count all individuals in a well-defined area or group. Sampling approaches include capture–recapture, distance sampling, and mark–recapture techniques, often combined with statistical models to estimate total abundance. Genetic methods can provide indirect estimates when physical counts are impractical. Challenges include imperfect detectability, biased sampling, changing boundaries of what constitutes the population, and temporal variation.

Population size is dynamic, influenced by births, deaths, immigration, and emigration. Growth can be modeled with exponential or logistic equations, the latter incorporating carrying capacity. Understanding size helps in conservation planning, disease control, wildlife management, and resource allocation. It also relates to related measures such as population density, age structure, spatial distribution, and genetic diversity. In humans, population size is tracked by censuses and vital statistics and informs policy, development, and epidemiology.