Forums Science Assignment Help Biology Describe the phenomenon of competitive exclusion


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    Organisms that live in close proximity interact with each other and some compete for the same resources. Describe the phenomenon of competitive exclusion, resource partitioning and character displacement.



    Competitive Exclusion refers to the Gause’s law of competitive exclusion principle. Although Gause himself never exactly defined what the Gause hypothesis is. According to the competitive exclusion principle, two similar species competing for the resource can never coexist together in the same niche. The competitively superior species will replace the less competitive species altogether. The two-species competing for the same resources must have to occupy a different niche. Niche is an ecological space in which the species survive.

    The competitive exclusion principle is based on results of Lotka-Volterra equation on competitive species independently given by Lotka in US and Volterra in Italy. These Lotka-Volterra equations are classical models on the competition which tells what will happen to the two-species living in the same niche, competing for the same resources, sharing the same place and when preying on each other.

    There are some examples in nature also in which similar species competing for the same resources co-exist also. The phytoplankton paradox is one such the marine and freshwater phytoplankton complete for a similar resource for the production of food and still co-exist together. The reason for this that natural communities have regular flux and not stable, and are not in equilibrium and exposed to continuously changing environment condition of weather, light, temperature, humidity. This is one of the limitations of competitive exclusion principle and other two limitations in which this Exclusion principle doesn’t come into play are it when the two-similar species are not competing.

    Character Displacement

    Character displacement is to reduce the competition between two similar species. This evolutionary consequence has led species to develop a different morphological character which led to their different feeding habits. One of the reasons for the character displacement is an assumption that too similar species if coexisting then to avoid interspecific competition must diverge.

    An example which illustrates this best is Darwin finches or Geospiza fortis. These finches fill the six criteria also for the evolutionary changes in existing population.

    1. Observation of diverges character should not be a chance phenomenon.
    2. There should be a genetic basis for divergence.
    3. There should be an evolutionary basis for the change in traits.
    4. The change in the type of food they consume should be able to be identified by their external appearance.
    5. There should not be the much significant difference in the environmental factor of sympatric and allopatric sites.
    6. There should be significant evidence which proves that the species are competing.

    Darwin Finches satisfy all these criteria.

    Resource Partitioning

    This is another way of avoiding interspecific competition that is resource partitioning. The similar species either moved to slightly different niche or have changed their behavior for feeding to avoid competition and increase their chances of survival. An example is of warbler species which come under the genus Dendroica inhabiting the boreal forest of New England. These five species of warblers feed on different branches of the trees, they also differ in their timing of feeding and nesting all co-exist together. These are black – barbarian, black-throated green, bay – breasted, Myrtle and cape may warblers.

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