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For example, with an annual growth rate of 4.8% the doubling time is 14.78 years, and a doubling time of 10 years corresponds to a growth rate between 7% and 7.5% (actually about 7.18%). When applied to the constant growth in consumption of a resource, the total amount consumed in one doubling period equals the total amount consumed in all ...
At first, the population growth rate is fast, but it begins to slow as the population grows until it levels off to the maximum growth rate, after which it begins to decrease (figure 2). The equation for figure 2 is the differential of equation 1.1 ( Verhulst's 1838 growth model ): [ 13 ]
Originally developed for growth modelling, it allows for more flexible S-shaped curves. The function is sometimes named Richards's curve after F. J. Richards , who proposed the general form for the family of models in 1959.
The standard logistic function is the logistic function with parameters =, =, =, which yields = + = + = / / + /.In practice, due to the nature of the exponential function, it is often sufficient to compute the standard logistic function for over a small range of real numbers, such as a range contained in [−6, +6], as it quickly converges very close to its saturation values of 0 and 1.
If we ignore the problem of how consumption is distributed, then the rate of utility is a function of aggregate consumption. That is, U = U ( C , t ) {\displaystyle U=U(C,t)} . To avoid the problem of infinity, we exponentially discount future utility at a discount rate ρ ∈ ( 0 , ∞ ) {\displaystyle \rho \in (0,\infty )} .
When calculating or discussing relative growth rate, it is important to pay attention to the units of time being considered. [ 2 ] For example, if an initial population of S 0 bacteria doubles every twenty minutes, then at time interval t {\displaystyle t} it is given by solving the equation:
Thus r is the maximum theoretical rate of increase of a population per individual – that is, the maximum population growth rate. 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 ...
In environmental science, optimum sustainable yield is the largest economical yield of a renewable resource achievable over a long time period without decreasing the ability of the population or its environment to support the continuation of this level of yield, and enables an ecosystem to have a high aesthetic value.