Law of Tolerance - Ecology [PDF]

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BASIC LAWS IN THE ECOSYSTEM



(Report by: Ellen Mae R. Orias) B. Law of Tolerance (Shelford's Law of Tolerance) It was develop by American zoologist Victor Ernest Shelford in 1911. It is a law stating that a certain organism’s survival and existence depend upon the multifaceted set of conditions wherein each individual has definite minimum, maximum and optimum ecological factors (or environmental factors) to establish success. This law is possibly the more precise indication of natural complexity and can be graphically indicated by this:



Shelford’s law of tolerance has “the concept of limiting effect of maximum and minimum”. The abundance or distribution of an organism can be controlled by certain factors where levels of these factors exceed the maximum or minimum limits of tolerance of that organism. Environmental factors (or abiotic components) involved climatic change, topographic location, temperature, salinity and biological necessities of both plants and animals. The organism will survive if the temperature, humidity, air, and other environmental factors are within the optimum range. And there are upper or lower limits to the physical factors an organism can tolerate.



Some subsidiary to the law of tolerance may be stated as follows: First, plants and animals may have a wide range of tolerance for one environmental factor but relatively narrow range of tolerance for another factor. Second, organisms with wide ranges of tolerance for all factors are likely to be most widely distributed. For further understanding of the law of tolerance here’s an example: The Antarctic fish “Trematomus Bernacchii” and desert fish “Pupfish Cyprinodon Macularius” provide an extreme contrast in limits of tolerances related to the very different environments in which they live. The Antarctic fish has a limit of temperature tolerance of less than 40C in the range of -20 to +20 and is thus extremely stenothermally cold adapted. In contrast the desert fish is eurythermal and is also euryhaline, tolerating temperatures between 100 and 400C, and salinities ranging from fresh water to that greater than sea water. Highlights: Each organism has its own higher and lower limit of tolerance. This capacity decides their distribution in environment. As we have emphasized, organisms are not just slaves to the physical environment, they adapt themselves and modify the physical environment so as to reduce the limiting effects of temperature, light, water and other physical conditions of existence.



References: Fairuz, Rafida Inas. 1 July 2018. SHELFORD’S LAW OF TOLERANCE. Retrieved January 28, 2019 from youtube.com: https://www.youtube.com/watch?v=MWiwUGcXvwc&t=84s A Dictionary of Zoology. (n.d.). Shelford’s Law of Tolerance. Retrieved January 28, 2019 from Encyclopedia.com: https://www.encyclopedia.com/plants-and-animals/zoology-andveterinary-medicine/zoology-general/shelfords-law-tolerance Biology Online Dictionary. 25 August 2014. Shelford’s Law of Tolerance. Retrieved January 28, 2019 from Biology Online.org: https://www.biology-online.org/dictionary/Shelfords_Law _of_Tolerance Oxfordreference.com. (n.d.). Shelford’s Law of Tolerance. Retrieved January 28, 2019 from http://www.oxfordreference.com/view/10.1093/oi/authority.20110803100500821