Organisms And Populations

In nature resources are finite, so populations follow logistic (Verhulst-Pearl) growth described by dN/dt = rN[(K-N)/K], producing a sigmoid or S-shaped curve. The term K represents the carrying capacity, the maximum population size that a particular habitat can sustainably support given its resources. As N approaches K, the factor (K-N)/K approaches zero, so the growth rate falls and the curve plateaus. The intrinsic rate of increase (r) determines how fast growth occurs but does not set the upper limit, so it is incorrect. Natality rate is merely the birth rate contributing to growth and is not the asymptote. Biotic potential is the maximum reproductive capacity under ideal conditions and relates to exponential, not logistic, limitation. As described in NCERT Class 12, Chapter 13 (Organisms and Populations), logistic growth is considered a more realistic model than exponential growth because no habitat has unlimited resources. The integrated logistic curve passes through a lag phase, then a phase of acceleration and deceleration, and finally a stationary phase where the population fluctuates around K. Plausibility check: at N = K the population stabilises with growth rate zero, and the three phases (lag, acceleration/deceleration, and stationary) match the S-shape, confirming that K is the limiting value.