Evans, Francis C. Division of Biological Sciences, University of Michigan, Ann Arbor, Michigan.
Last reviewed:January 2021
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- Principal types of dispersion
- Random or haphazard
- Clumped or contagious
- Analysis of dispersion
- Factors affecting dispersion
- Environmental agencies of transport
- Physical features of the habitat
- Influence of temporal changes
- Behavior patterns in reproduction
- Intensity of competition
- Social factors
- Optimal population density
- Related Primary Literature
- Additional Reading
The spatial distribution at any particular moment of the individuals of a species (typically plant or animal). Under natural conditions, organisms are distributed either by active movements, or migrations, or by passive transport by wind, water, or other organisms. The act or process of dissemination is usually termed dispersal, whereas the resulting pattern of distribution is best referred to as dispersion. Dispersion is a basic characteristic of populations (Fig. 1), controlling various features of their structure and organization. It determines population density, that is, the number of individuals per unit of area, or volume, and its reciprocal relationship, that is, mean area, or the average area per individual. It also determines the frequency, or chance of encountering one or more individuals of the population in a particular sample unit of area, or volume. Therefore, ecologists study not only the fluctuations in numbers of individuals in a population, but also the changes in their distribution in space. See also: Ecology; Ecosystem; Population dispersal; Population ecology
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