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=Vocabulary Word/Phrase= Logistic Growth 2

I. Explanation of what the word/phrase means in the context of human population dynamics
in most real populations both food and disease become important as conditions become crowded. There is an upper limit to the number of individuals the environment can support. Ecologists refer to this as the "carrying capacity" of the environment. Populations in this kind of environment show what is known as logistic growth.

Logistic population growth models density dependent population regulation. The model assumes that when populations increase in size (1) the per capita birth rate decreases (as a result of [|competition] for resources) and/or (2) the per capita death rate increases (as a result of competition for resources, [|predation], or the increased spread of disease). Thus, there is a population size at which the per capita birth rate equals the per capita death rate. At this population size, known as the [|carrying capacity], the [|population growth rate] is equal to zero.

II. Image representing the word/phrase
=Logistic growth curve=

From LokDoc
Jump to: [|navigation], [|search]A logistic growth curve. A **logistic growth curve** is a curve described by the following differential equation. It is usually used to model population growths. code dN/dt = r*N*(1-N/K)

code The K is called the //carrying capacity//. It is the maximum value that is sustainable by the curve and the curve will seek to stabilise at that level. The r is the //rate of maximum growth// and the N is the parameter value. [[|edit]]

Characteristics
A logistic growth curve that starts at a value less than K will slowly start to grow until it reaches a critical N when the curve will start growing at a very fast speed (think population growth). But the curve can't sustain an N higher than K so the growth will slow down and eventually stop when N equals K. The interesting part is the fast growth but regional growth which is desired in for instance [|soft-caps]. The effect of such a cap is hardly felt until a threshold is reached, then the effect grows very rapidly until it reaches a certain value when it almosts stops. It allows caps that only act on a specific bands of N and that (if desired) never really turn into a [|hard-caps], [[|edit]]

III. URLs for resources used
http://www.otherwise.com/population/logistic.html http://www.eoearth.org/article/Logistic_growth