What is the sigmoid population growth curve?

The sigmoid population growth curve is a pattern of growth in which a population's size increases slowly, then rapidly, before stabilising.

The sigmoid, or 'S' shaped, population growth curve is a common pattern observed in nature. It is characteristic of populations that are limited by environmental factors, such as food availability or space. The curve is divided into three distinct phases: the lag phase, the exponential phase, and the stationary phase.

In the lag phase, the population size increases slowly as the species becomes established in its environment. This is often a period of adjustment during which the population adapts to the conditions of its new habitat. The growth rate is low because the number of individuals who are reproducing is small.

The exponential phase follows the lag phase. During this phase, the population size increases rapidly. This is because the number of individuals who are reproducing is large, and the conditions are favourable for reproduction. The growth rate is high and the population size doubles during each time period. This phase continues until the population reaches the carrying capacity of the environment.

The stationary phase is the final phase of the sigmoid population growth curve. During this phase, the population size stabilises and remains relatively constant. This is because the rate of birth equals the rate of death. The population has reached the carrying capacity of the environment, which is the maximum number of individuals that the environment can support. The carrying capacity is determined by the availability of resources such as food, water, and space.

In summary, the sigmoid population growth curve is a model that describes how the size of a population changes over time. It is a useful tool for ecologists studying population dynamics, and it helps us understand how populations interact with their environment.