Carrying Capacity, Migration & Dispersion

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  • 0:12 Carrying Capacity
  • 1:51 Range
  • 2:29 Dispersion
  • 4:43 Migration
  • 5:38 Lesson Summary
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Lesson Transcript
Instructor: Joshua Anderson
Have you ever wondered why some types of birds fly south in the winter or why some animals form territories? Watch this video to learn about a species' maximum growth capabilities, the way its members group themselves and why they might migrate to new locations every year.

Carrying Capacity:

In an environment with favorable conditions, unlimited resources and no predation, populations can experience rapid and exponential growth or growth of a population where the number of individuals multiplies with every successive generation. This graph shows what unlimited exponential growth would look like. However, such conditions are rarely found in natural habitats, and exponential growth is usually observed in very small organisms under experimental conditions. In their natural habitat, all populations are limited by a number of factors which can include the size of the habitat, the amount of resources available, the population size of other competing species, predation and life history.

Population growth slows as it reaches its carrying capacity
Logistic Population Growth

Carrying capacity is the term used by biologists for the maximum stable population size that can be sustained over a long period of time. Many biologists have observed that as a natural population approaches its carrying capacity, its growth rate slows, and eventually the population stops growing when the carrying capacity is reached. This type of growth where the growth rate slows as the population reaches its carrying capacity is called logistic population growth. If a healthy population lives in a stable environment that has been undisturbed for a long period of time and it is not subject to heavy predation or hunting, chances are good that the population is at or near its carrying capacity. For example, mountain goat populations in the relatively undisturbed southern mountain ranges of Alaska are thought to be at or near carrying capacity.


One of the factors that determines a population's carrying capacity is its range or the geographic limits within which a population or individual lives. The larger that a population's range is, the more resources will be available to that population and the greater the carrying capacity will be if all other factors stay the same. Notice that within the definition of range both populations and individuals are mentioned. This is because individual organisms often do not use the entire range of the whole population. Instead, individual organisms often have their own smaller ranges within the population's range.


In addition, individual organisms within a population can show one of three different patterns of dispersion or pattern of spacing of individuals within a population. A population can show uniform, clumped or random dispersion.

Uniform dispersion patterns like this often arise as the result of intraspecific competition
Individual Territories

Most natural populations are spaced in either a uniform or clumped dispersion pattern. Uniform patterns are often a result of partitioning of resources among individuals resulting from intraspecific competition or competition for resources between individual organisms of the same species. Be careful that you don't confuse intraspecific competition with interspecific competition which you may remember is when two or more species in a community are competing for resources. One trick to remember the difference is that IntrAspecific competition occurs within A population of A single species and that IntErspecific competition occurs bEtwEEn different species. In other words, if it has an a in it, it occurs within a population and if it has an e in it, it occurs between different species.

Intraspecific competition often results in the formation of individual territories, each of which is controlled by an individual organism of the population. In this picture, we can see the individual territories that these fish have defined for themselves by the hexagonal depressions that they have made in the sand.

Clumped dispersion patterns

These penguins display a clumped dispersion pattern to conserve heat
Clumped Dispersion Pattern

Random dispersion patterns do occur but are much less common because there is usually a driving force in a population that favors either clumped or uniform dispersion.

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