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"as a population of populations which go extinct locally and recolonize." [30]: 105 Metapopulation ecology is a simplified model of the landscape into patches of varying levels of quality. [31] Patches are either occupied or they are not. Migrants moving among the patches are structured into metapopulations either as sources or sinks.
Source–sink dynamics is a theoretical model used by ecologists to describe how variation in habitat quality may affect the population growth or decline of organisms.. Since quality is likely to vary among patches of habitat, it is important to consider how a low quality patch might affect a population.
One of the most basic and milestone models of population growth was the logistic model of population growth formulated by Pierre François Verhulst in 1838. The logistic model takes the shape of a sigmoid curve and describes the growth of a population as exponential, followed by a decrease in growth, and bound by a carrying capacity due to ...
A population ecology concept is r/K selection theory, one of the first predictive models in ecology used to explain life-history evolution. The premise behind the r/K selection model is that natural selection pressures change according to population density. For example, when an island is first colonized, density of individuals is low.
This is a graph of population change utilizing the logistic curve model. When the population is above the carrying capacity it decreases, and when it is below the carrying capacity it increases. When the Verhulst model is plotted into a graph, the population change over time takes the form of a sigmoid curve, reaching its highest level at K.
Consider a population at harvested at a constant harvest level . If the population falls (due to a bad winter or illegal harvest) this will ease density-dependent population regulation and increase yield, moving the population back to , a stable equilibrium. In this case, a negative feedback loop creates stability.
The model can also be written in the form of a differential equation: = with initial condition: P(0)= P 0. This model is often referred to as the exponential law. [5] It is widely regarded in the field of population ecology as the first principle of population dynamics, [6] with Malthus as the founder.
The concept is commonly used in insect population ecology or management to determine how environmental factors affect the rate at which pest populations increase. See also exponential population growth and logistic population growth. [18]