Dr. Ray L. Winstead
Professor of Biology, Indiana University of Pennsylvania

Limiting Factors


Definition of Limiting Factor: A limiting factor is an environmental factor essential for life that is absent or depleted below the critical minimum, or that exceeds the maximum tolerable level for the species.


Liebig's Law of the Minimum: The growth, reproduction, and survival of an organism is dependent upon the nutrient substance that is available in minimum quantity.


Shelford's Law of Tolerance: Absence or failure of an organism can be controlled by the qualitative or quantitative deficiency or excess with respect to any one of several factors (limiting factors) that may approach the limits of tolerance for that organism.


Ecological Principles Associated with the Law of Tolerance:


        1. Organisms may have a wide range of tolerance for one factor and a narrow range for another.


        2. Organisms with wide ranges of tolerance for basically all factors are likely to be most widely distributed.


        3. Definition: Within the limits of tolerance for some particular factor for some species, an optimum level is that level at which the species is best suited.


            Principle: When conditions are not optimum for a species with respect to one ecological factor, the limits of tolerance with respect to other ecological factors may be reduced, because of the interactions of factors.


        4. The limits of tolerance for adult reproductive individuals and any young organism, e.g., seeds, eggs, embryos, seedlings, and larvae are usually narrower than for non-reproductive adults.



        The physical environment, to a large extent, determines what organisms may exist in a particular place.


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Dr. Ray L. Winstead
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