Example Of Density Independent Factor

45.2C: Density-Dependent and Density-Independent Population Regulation

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Learning Objectives

Differentiate between density-dependent and density-independent population regulation.

Density-dependent regulation

In population environmental, density-dependent processes occur when population growth rates are regulated by the density of a population. Most density-dependent factors, which are biological in nature (biotic), include predation, inter- and intraspecific competition, accumulation of waste matter, and diseases such as those acquired by parasites. Usually, the denser a population is, the greater its mortality rate. For instance, during intra- and interspecific contest, the reproductive rates of the individuals will commonly be lower, reducing their population's rate of growth. In improver, low prey density increases the mortality of its predator because it has more difficulty locating its food source.

An instance of density-dependent regulation is shown with results from a study focusing on the giant intestinal roundworm (Ascaris lumbricoides), a parasite of humans and other mammals. The data shows that denser populations of the parasite exhibit lower fecundity: they contained fewer eggs. 1 possible explanation for this phenomenon was that females would be smaller in more dense populations due to limited resources then they would have fewer eggs. This hypothesis was tested and disproved in a 2009 report which showed that female weight had no influence. The bodily cause of the density-dependence of fecundity in this organism is withal unclear and awaiting further investigation.

Figure \(\PageIndex{ane}\): Effect of population density on fecundity: In this population of roundworms, fecundity (number of eggs) decreases with population density.

Density-contained regulation and interaction with density-dependent factors

Many factors, typically physical or chemical in nature (abiotic), influence the mortality of a population regardless of its density. They include weather, natural disasters, and pollution. An private deer may be killed in a wood burn down regardless of how many deer happen to be in that area. Its chances of survival are the same whether the population density is high or low.

In existent-life situations, population regulation is very complicated and density-dependent and contained factors can collaborate. A dense population that is reduced in a density-independent way by some environmental factor(southward) will be able to recover differently than would a sparse population. For example, a population of deer afflicted by a harsh wintertime will recover faster if there are more deer remaining to reproduce.

Key Points

The density of a population tin be regulated past diverse factors, including biotic and abiotic factors and population size.
Density-dependent regulation tin can be affected by factors that affect nativity and decease rates such as competition and predation.
Density-independent regulation can be affected by factors that touch birth and death rates such as abiotic factors and environmental factors, i.e. astringent weather condition and weather condition such equally burn down.
New models of life history incorporate ecological concepts that are typically included in r- and K-selection theory in combination with population age structures and bloodshed factors.

Cardinal Terms

interspecific: existing or occurring betwixt dissimilar species
intraspecific: occurring among members of the same species
fecundity: number, rate, or capacity of offspring product

Contributions and Attributions

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OpenStax College, Environmental Limits to Population Growth. Oct 17, 2013. Provided by: OpenStax CNX. Located at: http://cnx.org/content/m44872/latest...e_45_03_01.jpg . License: CC By: Attribution
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