Competitive exclusion, principle

The contextuality of meaning may be called a principle , for it is neither a brute fact nor a law of nature. But exactly what is meant by a principle is hard to specify. We can give some familiar examples of course. In ecology there is the well-known competitive exclusion principle , which explains why organisms occupying exactly the same niche cannot coexist for more than a brief period of time. In logic we all use, whether we know it or not, the principle of contradiction , which states that two propositions that really contradict each other cannot both be true. And since, by implication, at least one of them must be false, we justify the kind of hypothetico-deductive scientific... 

The grossly different values for the two closely related Vaccinium species which usually do not occur next to each other hence are probably results of different metal acquisition strategies rather than due to the competitive exclusion principle both plant species differ in spatial distribution rather than in take-up of resources (for example, both are rich in manganese while the differences can be seen in pairs of other metals). 

Pure and simple competition has a strong tendency to result in the exclusion of one of the competitors, and various attempts to formulate a competitive exclusion principle have appeared in the literature. One such formulation, which is supported by many experiments as well as by the predictions of mathematical models, is that pure and simple competitors will not coexist indefinitely in a system that is spatially homogeneous and that is subject to time-invariant external influences. For example, the prediction is that pure and simple competitors will not coexist in a well-mixed chemostat having a vanishingly small surface-to-volume ratio (so that the spatial heterogeneity due to the presence of the chemostat walls is negligible) if the dilution rate and temperature of the chemostat, the composition of feed to the chemostat, etc., are all Independent of time. Moreover, the prediction is that not only will the competitors not coexist in a steady state in such a system but that they will not even coexist in a perpetually transient state, such as sustained oscillations of their population densities see Fredrickson and Stephanopoulos (M for a discussion of the literature on these points. 

Some years ago A. L. Koch (14) published computer simulations of situations in which two predator populations competed purely and simply for one prey population. Koch s simulations showed these three populations coexisting in what appeared to be limit cycles, a clear violation of the competitive exclusion principle stated above, but since his simulations were based on Lotka-Volterra type equations whch I consider to be quite Inappropriate for microbial populations, 1 disregarded his results and did not see their significance. Similar results published by Hsu al. 

The drug price intervention system in place in Spain since 1991 is based on the fixing of the price of each product by the health authorities, calculated according to its cost . This system allows for the possibility of excluding certain products or therapeutic groups from the price intervention system. It would be desirable to apply this exclusion principle to those products that are subject to a reasonable level of competition. Briefly, the main features of the Spanish system of price regulation are as follows ... 

Niche exclusion principle In a competition between species that seek to exploit the same niche, only one species survives. 

Microorganisms approved for feed use under the EU regulations comprise Enterococcus faecium (in various forms) and Saccharomyces ceremsiae. Their use as probiotics (as an alternative to antibiotics) is based on the principle of promoting the growth of lactobacilli and reducing the numbers of enteropathogenic bacteria in the gut. Sometimes this principle is referred to as competitive exclusion. This aspect will be addressed in more detail in Chapter 7 (this volume). 

Shaw and Bell (1991) examined this effect in the case of competition between radiocaesium and the K+ and NH4+ ions during root uptake by wheat (Triticum aestivum). These authors formalised the observed relationships in terms of classical Michaelis-Menten kinetics which necessitates the assumption that each of these ions is taken up by identical sites associated with the root plasmalemma. Lembrechts et al. (1990) found a similar negative and non-linear relationship between the concentration of Ca either in soil or in solution culture and the degree of radiostrontium uptake by lettuce Lactuca saliva). The principle of competitive exclusion of a radionuclide by an ion analogue may be exploited, with varying degrees of success, as a post-con-... 

On the basis of the simple Hiickel theory, the two NMBOs of both 33 and 34 will be degenerate. Hund s rule therefore dictates a triplet state. However, Borden and Davidson argued that since the electrons in the two NBMOs of 33 are specially isolated and have reduced the electrostatic repulsion, the singlet state will not violate the Pauli s exclusion principle and will be energy competitive with the triplet... 

Theorem 5.1 is an example of the principle of competitive exclusion only one competitor can survive on a single resource. Many of the well-known... 

R. McGehee and R.A. Armstrong. Some mathematical problems concerning the ecological principle of competitive exclusion. J. Diff. Equations, 23 30-52, 1977. 

The concept of competitive exclusion involves the purposeful inoculation of animals with a desirable gut microflora. This is not a nutrient-based supplementation. However, an oral route of inoculation is used, and the potential of competitive exclusion for improving food safety is substantial. Thus, a brief discussion of this principle is provided. 

Curtin-Hammett In stereogenic reactions leading from a substrate to two diastereomers, it is irrelevant Principle which conformer of the substrate is preferred if conformational isomerization is much faster than the reaction. The favored reaction is the one that takes place via the transition state with the lowest energy and may or may not derive from the preferred conformation of the substrate. The extent of diastereoselectivity encountered in the stereogenic reaction under scrutiny results from the competition between the favored and the disfavored reaction paths it depends exclusively on the free enthalpy difference between the competing, diastereomeric transition states. 

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