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6.13 The logistic equation

Example.

The logistic equation The logistic equation is the differential equation

dNdt=rN(1-NK)\frac{dN}{dt}=rN\left(1-\frac{N}{K}\right)

where N(t)N(t) is the dependent variable and r,Kr,K are positive constants.

The logistic equation can be used to model population growth, where N(t)N(t) signifies the number of individuals in a population at time tt. The idea is that for a small population (NKN\ll K) the growth rate is roughly proportional to NN, but as NN increases then competition for resources slows the growth rate (or increases the death rate), i.e. as NN tends towards KK then the factor 1-N/K1-N/K tends to zero, reducing the growth rate towards zero.