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In other words, a factor is limiting if a change in the factor produces increased growth, abundance, or distribution of an organism when other factors necessary to the organism's life do not. Limiting factors may be physical or biological. [4]: 417, 8 Limiting factors are not limited to the condition of the species.
There also exists density-independent inhibition, where other factors such as weather or environmental conditions and disturbances may affect a population's carrying capacity. [ citation needed ] An example of a density-dependent variable is crowding and competition.
The first variable is r (the intrinsic rate of natural increase in population size, density independent) and the second variable is K (the carrying capacity of a population, density dependent). [21] It is important to understand the difference between density-independent factors when selecting the intrinsic rate and density-dependent for the ...
The organisms may not actually come into contact and only interact via the shared resource indirectly. For instance, exploitative competition has been shown experimentally between juvenile wolf spiders (Schizocosa ocreata). Both increasing the density of young spiders and reducing the available food supply lowered the growth of individual spiders.
Liebig's law has been extended to biological populations (and is commonly used in ecosystem modelling).For example, the growth of an organism such as a plant may be dependent on a number of different factors, such as sunlight or mineral nutrients (e.g., nitrate or phosphate).
The causes of delayed density dependence vary in each situation. In lemmings, food supply and predation are the most important factors that lead to delayed density dependence. [3] Competition between life stages is another cause. In some species of moth the practice of egg cannibalism takes place where older moths eat eggs of their own species. [6]
Biotic factors such as predation, disease, and inter- and intra-specific competition for resources such as food, water, and mates can also affect how a species is distributed. For example, biotic factors in a quail's environment would include their prey (insects and seeds), competition from other quail, and their predators, such as the coyote. [5]
A cohort life table tracks organisms through the stages of life, while a static life table shows the distribution of life stages among the population at a single point in time. [3] Following is an example of a cohort life table based on field data from Vargas and Nishida (1980). [4]