Notes

Types of Population Regulation in Ecology

Population regulation is the ecological process that helps control or limit the growth of populations by affecting the birth and death rates. Various mechanisms help in regulating the population. The factors that enable such mechanisms or limit the birth or death rate can be density-dependent or density-independent. Thus, there are different types of population regulation in ecology.

Types of Population Regulation in Ecology

Density-Dependent Factors

Such limiting factors are biotic. They also include diseases, predation competition for resources, etc, that affect as a function of population density. For example, the growing population of one species causes competition among species, which either causes a reduced birth rate or an increased death rate. Both these scenarios cause a decline in reproductive rate and population density. An increase in prey species results in higher predation rates.

Density-dependent limiting factors generally cause populations to reach a maximum level known as their carrying capacity. At its carrying capacity, the population size becomes stable and is called logistic growth. A stable population continues to grow larger at an increased pace known as exponential growth.

Density-dependent factors can affect either negatively ot positively. When it causes a reduced birth rate or increased death rate, the impact is negative feedback. When these factors cause an increase in population size, it is called a positive feedback or Allee effect.

Populations that experience density-dependent limiting factors are often insatiable, and experience cycles of growth followed and a reduction in size in a pattern known as cyclical oscillations. Predation is an example of cyclical oscillation involving multiple species.

Density-Independent Factors

Density-independent factors are abiotic, such as natural disasters that affect a fraction of the population, no matter how small or large the population. These factors are not dependent on the population’s size. But they can be more catastrophic to a small population of species that are in a limited geographic range.

Top-Down Population Regulation

Top-down population regulation is where the species from a higher trophic level controls the population of a species in a lower trophic level. For example, predators regulate the population of their prey species at a lower level. Such population regulation is known as “predator-controlled” regulation.

Bottom-Up Population Regulation

Bottom-up population regulation depends on the resources of the ecosystem. The species in higher trophic levels depend on the species of lower trophic levels. Due to this, an absence or reduction in the lower-level population affects the higher levels.

References

https://www.studysmarter.co.uk/explanations/biology/ecology/population-regulation/
Shukla, R.S. and Chandel, P.S. (2001) Plant Ecology. S. Chand and Company Ltd., New Delhi.
Verma, P.S., Agarwal, V.K. (1999). Cell Biology, Genetics, Molecular Biology, Evolution, and Ecology. New Delhi: S.Chand Co.(Pvt) Ltd.