<P> Population ecology 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 change over time and space . The term population ecology is often used interchangeably with population biology or population dynamics . </P> <P> 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 . </P> <Table> Terms used to describe natural groups of individuals in ecological studies <Tr> <Th> Term </Th> <Th> Definition </Th> </Tr> <Tr> <Td> Species population </Td> <Td> All individuals of a species . </Td> </Tr> <Tr> <Td> Metapopulation </Td> <Td> A set of spatially disjunct populations, among which there is some immigration . </Td> </Tr> <Tr> <Td> Population </Td> <Td> A group of conspecific individuals that is demographically, genetically, or spatially disjunct from other groups of individuals . </Td> </Tr> <Tr> <Td> Aggregation </Td> <Td> A spatially clustered group of individuals . </Td> </Tr> <Tr> <Td> Deme </Td> <Td> A group of individuals more genetically similar to each other than to other individuals, usually with some degree of spatial isolation as well . </Td> </Tr> <Tr> <Td> Local population </Td> <Td> A group of individuals within an investigator - delimited area smaller than the geographic range of the species and often within a population (as defined above). A local population could be a disjunct population as well . </Td> </Tr> <Tr> <Td> Subpopulation </Td> <Td> An arbitrary spatially delimited subset of individuals from within a population (as defined above). </Td> </Tr> </Table>

In population growth mathematical models the letter k stands for