Carrying Capacity of a Population: Definition & Explanation

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  • 0:00 Carrying Capacity of a…
  • 0:52 Fluctuations in…
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Lesson Transcript
Instructor: Sarah Friedl

Sarah has two Master's, one in Zoology and one in GIS, a Bachelor's in Biology, and has taught college level Physical Science and Biology.

As population size increases, so does the demand for resources. Carrying capacity helps define the appropriate size of a population based on its environment. The availability of resources has a direct effect on how quickly and how large a population can grow.

Carrying Capacity of Population

As a new population grows in an environment, it will experience what is called exponential growth. This means that the population grows very quickly over a short amount of time. On a graph, exponential growth looks like the letter 'J.' However, since resources are limited, no environment can support this type of growth for very long. The growth of the population begins to level out and takes the shape of an 'S.' This type of population growth is called logistic growth.

carrying capacity

As population growth becomes more restricted, and the size of the population reaches stability, that population reaches its carrying capacity. On this graph, carrying capacity is marked by the line K. This carrying capacity is the population size that a certain environment can sustain, or carry. The value of K will vary depending on the species and resources available in the habitat.

Fluctuations in population growth

In theory, populations grow quickly, reach K, and level out. In reality, populations tend to fluctuate around K, and there are several ways this might occur in nature.

Carrying capacity fluctuations can be chaotic. These are erratic fluctuations around K, often due to environmental factors that have an immediate impact on population size. Disease and natural disasters may cause chaotic fluctuations.

Fluctuations around K can also be cyclical. A cyclical fluctuation in population growth repeats itself and is called the stable limit cycle. This type of oscillation around K is different from chaotic because it is regular and produces a normal pattern for the population.

Damped oscillations are fluctuations of population size above and below K that lessen with time. The population will eventually reach a stable limit, and the fluctuations will become minimal.

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