Carrying Capacity, Migration and Dispersion
- Track Progress
- 0:12 Carrying Capacity
- 1:51 Range
- 2:29 Dispersion
- 4:43 Migration
- 5:38 Lesson Summary
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.
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.
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.
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 can occur when resources are concentrated in specific areas of a habitat, and the organisms, in turn, become concentrated around these resource rich areas. Clumped dispersion patterns are also seen as a result of social interactions within a population. For example, animals that live in herds or packs for social reasons have a clumped dispersion pattern. In the picture shown here, these emperor penguins are exhibiting a clumped dispersion pattern to conserve heat.
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.
Some species of animals stay in the same location all of their lives. However, other species move from place to place. Many animal species travel in a yearly migration which is the seasonal movement of organisms over long distances. Availability of food appears to be the most common reason for migration. For example, the annual migration of the wildebeest of the Serengeti-Mara Ecosystem is timed to take advantage of the growth of grasses after seasonal rainy periods in different parts of the wildebeest range. Bird migrations also seem to be mostly motivated by availability of food. However, some migrations appear to be motivated, at least partially, by seasonal variations in temperature. In either case, migrations allow populations to increase their range and resource pool and therefore, have the ability to increase a population's carrying capacity.
Let's do a quick review. A population's carrying capacity is the maximum stable population size that can be sustained over a long period of time. It has been 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 .
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.
Dispersion is the pattern of spacing of individuals within a population. A population can show uniform, clumped or random dispersion. 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.
Migration is the seasonal movement of organisms over long distances. Migrations allow populations to increase their range and resource pool and therefore, have the ability to increase a population's carrying capacity.
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Chapters in Biology 101: Intro to Biology
- 1. Science Basics (6 lessons)
- 2. Review of Inorganic Chemistry For Biologists (14 lessons)
- 3. Introduction to Organic Chemistry (8 lessons)
- 4. Nucleic Acids: DNA and RNA (4 lessons)
- 5. Enzymatic Biochemistry (4 lessons)
- 6. Cell Biology (14 lessons)
- 7. DNA Replication: Processes and Steps (5 lessons)
- 8. The Transcription and Translation Process (10 lessons)
- 9. Genetic Mutations (4 lessons)
- 10. Metabolic Biochemistry (9 lessons)
- 11. Cell Division (13 lessons)
- 12. Plant Biology (12 lessons)
- 13. Plant Reproduction and Growth (10 lessons)
- 14. Physiology I: The Circulatory, Respiratory, Digestive,... (12 lessons)
- 15. Physiology II: The Nervous, Immune, and Endocrine Systems (13 lessons)
- 16. Animal Reproduction and Development (12 lessons)
- 17. Genetics: Principles of Heredity (10 lessons)
- 18. Principles of Ecology (18 lessons)
- 19. Principles of Evolution (9 lessons)
- 20. The Origin and History of Life On Earth (4 lessons)
- 21. Phylogeny and the Classification of Organisms (7 lessons)
- 22. Social Biology (6 lessons)
- 23. Basic Molecular Biology Laboratory Techniques (13 lessons)
- 24. Analyzing Scientific Data (3 lessons)
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