Comepetition

Competition

	Competition Competition occurs when two populations use the same source of nutrition hence they achieve lower growth rates. Competition also brings about ecological separation of closely related population (competitive exclusion principle). Thus no two population can occupy the same niche. For example, in the case of Paramaecium caudatum and P. Aurelia individually they maintain a constant population level but when the protozoans are placed together, it was seen that P.aurelia survived after 16 days. In another experiment two organisms (P. caudatum and P. bursaria) were artificially grown in conical flasks.
Both were able to survive and reach a stable equilibrium even when grown together. It was evident that they competed for the same source but the two populations occupied different regions of the flasks. Thus in order to coexist, the two population chose different habitats to allow the two species to grow together. Growth rates of competing population vary under different environmental conditions. In marine habitats, psychrophilic (cold loving) and mesophilic (that grow in moderate temperatures, i.e. 25-35°C) organisms occur together under same nutrient conditions.
At low temperature, psychrophilic organisms grow and under moderately high temperatures, mesophilic organisms grow. At high substrate concentration, competition between a marine Spirillum and E.coli results in competitive exclusion of Spirillum whereas at low concentration of substrate, the reverse occurs and the E.coli is excluded. From this we can conclude that abiotic parametes such as temperature, pH, oxygen, etc. greatly influence the growth rates of microbial population.

Similarly, dominant microbial populations in sewage (having a high organic substrate content) are rapidly displaced in competition with the autochthonous microbial population of receiving streams and rivers, where the concentration of organic matter diminishes in the course of mineralisation and dilution.Under conditions of drought, the more tolerant species displace the more sensitive ones owing to the competitive ability of the former to survive. Competition is seen for multiple resources between two or more microbial species as in the case of Microcystis aeruginosa and the diatom Asterionel1a formosa. Microcystis utilises phosphorus as essential source but does not require silicon whereas Asterionel1a requires both silicon and phosphorus. Hence proportion of Microcystis decreases with an increase in silicon or phosphorus supply

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