It's been 10 years now since the definition of POPULATION given by Ernest Callenbach first appeared in his “pocket-guide” called Ecology. The definition is provided below so that the reader of the SUSTAINABILITY definition will have the context of the meaning of POPULATION. Please read the definition of POPULATION below.
P O P U L A T I O N
You probably know the human population of your town or city, at least roughly. Ecologically speaking a population is simply a collection of members of one SPECIES in the same place at the same time - people, other animals, plants, PROTISTS, or BACTERIA. Life is never lived as single individuals. Individuals always reproduce to form populations larger or small.
In theory, within an ECOSYSTEM each species tends to increase its population until it reaches the ecosystem's CARRYING CAPACITY. But in fact populations of most species usually neither rise above a level at which their HABITATS would be destroyed nor decline below a level at which EXTINCTION is a serious danger. Populations in an area is limited by PREDATION by other species through territoriality (a male bird, for example, lays exclusive claim to a certain territory and drives away rivals); ... [to be compiled completely at a later time].
Robert "Roy" van de Hoek
Populations are very complex and are beautiful too. This interesting and simple explanation of a population by Ernest Callenbach entices the reader to continue further to understand how it all fits into the big picture of ECOLOGY.