Dynamic Equilibrium & Density-dependent Factors

Understanding Dynamic Equilibrium

In ecology, dynamic equilibrium refers to a state where the population size remains relatively stable over time, despite ongoing processes that might change it. This balance occurs because the rates of birth and immigration are equal to the rates of death and emigration.

For example:

• In a forest, the number of new trees growing is balanced by the number of trees dying, maintaining a stable tree population.

Characteristics of Dynamic Equilibrium

• Stability: Population size does not change drastically over time.
• Balance of Rates: Birth and immigration rates equal death and emigration rates.
• Feedback Mechanisms: Natural systems have feedback loops that help maintain equilibrium.

Density-dependent Factors

Density-dependent factors are factors whose effects on the size or growth of the population vary with the population density. These factors tend to stabilize population size by increasing mortality or reducing birth rates as the population becomes more crowded.

• Competition: As population density increases, individuals compete more for limited resources like food and space.
• Predation: Higher population density can lead to increased predation as predators find it easier to locate prey.
• Disease: Diseases spread more easily in densely populated areas, increasing mortality rates.
• Parasitism: Like diseases, parasites can spread more rapidly in crowded conditions.

Examples of Density-dependent Factors

• In a pond, as the fish population grows, food becomes scarce, leading to increased competition and reduced growth rates.
• In a crowded city, diseases like the flu spread more quickly due to close contact between individuals.