Population dynamics is the study of marginal and long-term changes in the numbers, individual weights and age composition of individuals in one or several populations, and biological and environmental processes influencing those changes. Main articles: Life All organisms (viruses not included) consist of cells, which in turn, are based on a common carbon-based biochemistry. ... In politics and other non-technical contexts, nature or (the) (natural) environment often refers to that part of the natural world that people deem important or valuable, for any reason — economic, aesthetic, philosophical, hedonistic, sentimental, etc. ...

Population dynamics has tradionally been the dominant branch of mathematical biology, which has a history of more than 200 years, although more recently the scope of mathematical biology has greatly expanded. The early period was dominated by demographic studies such as the work of Benjamin Gompertz and Pierre François Verhulst in the early 19th century, who refined and adjusted the Malthusian demograhical model. Mathematical biology or biomathematics is an interdisciplinary field of academic study which aims at modelling natural, biological processes using mathematical techniques and tools. ... Demography is the study of human population dynamics. ... Benjamin Gompertz (March 5. ... Pierre François Verhulst (October 28, 1804 - February 15, 1849, Brussels, Belgium) was a mathematician and a doctor in number theory from the University of Ghent in 1825. ... The Rev. ...

A more general model formulation was proposed by F.J. Richards in 1959, by which the models of Gompertz, Verhulst and also Ludwig von Bertalanffy are covered as special cases of the general formulation. The computer game SimCity and the MMORPG Ultima Online, among others, tried to simulate some of these population dynamics. Population dynamics also attempts to study topics such as aging populations or population decline. 1959 was a common year starting on Thursday of the Gregorian calendar. ... ... A computer game is a game composed of a computer-controlled virtual universe that players interact with in order to achieve a defined goal or set of goals. ... A screenshot of SimCity on the Atari ST SimCity is a real-time strategy/simulation city-building computer game (or software toy). It is game developer Maxis flagship product. ... A massively (or massive) multiplayer online role-playing game or MMORPG is a multiplayer computer role-playing game that enables thousands of players to play in an evolving virtual world at the same time over the Internet. ... Released on September 30, 1997, by Origin Systems, Ultima Online (UO) is often considered the first popular massively multiplayer computer game. ... A computer simulation or a computer model is a computer program which attempts to simulate an abstract model of a particular system. ... In demographics population ageing occurs when the average age of a regions population gets older. ... In demographics population decline is a fall in a regions population. ...

In Fisheries and Wildlife management, population is affected by three dynamic rate functions. Density of individuals in a population effects all three rate functions.

• Natality or birth rate, often recruitment, which means reaching a certain size or reproductive stage. Usually refers to the age a fish can be caught and counted in nets
• Growth rate, which unlike natality, measures the growth of individuals in size and length. More important in fisheries, where population is often measured in biomass.
• Mortality, which includes harvest mortality and natural mortality. Natural mortality includes non-human predation, disease and old age.

Immigration and emmigration are present, but are usually not measured.

All of these are measured to determine the Harvestable surplus, which is the number of individuals that can be harvested from a population without effecting long term stability, or average population size. The harvest within the harvestable surplus is considered Compensatory Mortality, where the harvest deaths are substituting for the deaths that would occur naturally. Harvest beyond that is Additive Mortality, harvest in addition to all the animals that would have died naturally. These terms are not the universal good and evil of population management, for example, in deer, the DNR are trying to reduce deer population size overall to an extent, since hunters have reduced buck competition and increased deer population unnaturally.

See also:

• System dynamics
• Volterra-Lotka equations
• population genetics