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Population ecology or autoecology is a sub-field of ecology that deals with the dynamics of species populations and how these populations interact with the environment. It is the study of how the population sizes of species groups change over time and space. The development of population ecology owes much to demography and actuarial life tables. Population ecology is important in conservation biology, especially in the development of population viability analysis (PVA) which makes it possible to predict the long-term probability of a species persisting in a given habitat patch. Although population ecology is a subfield of biology, it provides interesting problems for mathematicians and statisticians who work in population dynamics. ==Fundamentals== The most fundamental law of population ecology is Thomas Malthus' exponential law of population growth.
This principle in population ecology provides the basis for formulating predictive theories and tests that follow: Simplified population models usually start with four key variables (four demographic processes) including death, birth, immigration, and emigration. Mathematical models used to calculate changes in population demographics and evolution hold the assumption (or null hypothesis) of no external influence. Models can be more mathematically complex where "...several competing hypotheses are simultaneously confronted with the data." For example, in a closed system where immigration and emigration does not take place, the per capita rates of change in a population can be described as: : where ''N'' is the total number of individuals in the population, ''B'' is the raw number of births, ''D'' is the raw number of deaths, ''b'' and ''d'' are the per capita rates of birth and death respectively, and ''r'' is the per capita average number of surviving offspring each individual has. This formula can be read as the rate of change in the population (''dN/dT'') is equal to births minus deaths (B - D).〔 Using these techniques, Malthus' population principle of growth was later transformed into a mathematical model known as the logistic equation: : where ''N'' is the biomass density, ''a'' is the maximum per-capita rate of change, and ''K'' is the carrying capacity of the population. The formula can be read as follows: the rate of change in the population (''dN/dT'') is equal to growth (''aN'') that is limited by carrying capacity ''(1-N/K)''. From these basic mathematical principles the discipline of population ecology expands into a field of investigation that queries the demographics of real populations and tests these results against the statistical models. The field of population ecology often uses data on life history and matrix algebra to develop projection matrices on fecundity and survivorship. This information is used for managing wildlife stocks and setting harvest quotas 〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Population ecology」の詳細全文を読む スポンサード リンク
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