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Long Answer Questions · Q24

Q.With the help of the Verhulst-Pearl logistic growth equation, explain how the rate of population growth slows as population size approaches the carrying capacity (K) of the environment.

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The Verhulst-Pearl logistic growth equation, dN/dt = rN(K − N)/K, describes population growth under the realistic condition of a finite, limited environment, where N is the current population size, r is the intrinsic rate of natural increase, and K is the carrying capacity — the maximum population size the environment can sustainably support given its available resources.

The key to understanding how growth slows lies in the additional factor (K − N)/K, which is not present in the simpler exponential growth equation. When the population size N is very small relative to the carrying capacity K, the numerator (K − N) is nearly equal to K, so the factor (K − N)/K is close to 1 — in this situation, growth proceeds at very nearly the same rate as unrestricted exponential growth, since the population is still far from straining the environment's resources.

As N grows and gets closer to K, however, the numerator (K − N) shrinks, so the factor (K − N)/K itself shrinks toward zero. Multiplying rN by an ever-smaller fraction means the overall growth rate dN/dt itself becomes smaller even though the population is larger — in other words, growth actively decelerates as resources become scarcer relative to demand. …

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