1.3. Population systemPopulation system (or a life-system) is a
population with its effective environment. The term "life-
system" was introduced by Clark et al. (1967). Later, Berryman
(1981) suggested another term "population system" which is
definitely better. A short review of the life-system methodology
was published by Sharov (1991). Major components of a population
system Temporal and spatial structure of a population system
Dynamics of Population SystemsFactor-Effect concept:
Environmental factors affect population density. When factors
change then population density changes respectively. Advantage:
Causal explanation of population change Disadvantage: It is
useful for one-step instant effects but becomes confusing if the
effect is simultaneously a factor that causes soemthing else, or
if there are time delays in the effect. Factor-Process concept:
Environmental factors do not affect population density directly,
instead they affect the rate of various ecological processes
(mortality, reproduction, etc.