One possible outcome of intraspecific competition is that superior competitors will have greater fitness than lesser competitors will. This is often the case in lower density populations. Chpt 56, pgs 1187-1194) Terminology: paramecium/paramecia (look at online site such as Wikipedia) stable coexistence vs. competitive exclusion competitive exclusion principle (you may be asked to state it – It is best to memorize it) … Interspecific competition is the basis of the competitive exclusion principle, which states that two different species cannot occupy the same niche in the same place for very long. We contrasted the fit of these models with two types of models that are considered to be consistent with different outcomes of interspecific competition. •The competitive exclusion principle: two species with similar needs for the same limiting resources cannot coexist in the same place. •There is potential for competition between any two species that need the same limited resource. Scenario 1 ( Figure 5 ). Four possible scenarios may result from interspecific competition of two species and the outcome depends on how the two isoclines are in relation to one another. Interspecific competition can be studied using mathematical models that have been specifically developed for the purpose by ecologists. This can lead to one of two possible outcomes. This is of two types: (i) Interspecific competition occurs between the individuals of the same species and their requirements are common and, (ii) Interspecific competition occurs between individuals of two different species occurring in a habitat. An alternative explanation for the reduced abundance of P. semipunctata is asymmetric interspecific competition between the two species. The two isoclines do not cross and the isocline of population X 1 is above that of X 2 . To test this hypothesis, equal larval densities of each species were introduced into host logs. • Competition. B) Explain the difference between the two forms you identified in above (A) - i.e. 5. When two closely-related species find themselves occupying the same geographic location (sympatric), their requirements for the necessities of life are probably so similar that they are forced into intense interspecific competition. •Interspecific competition for resources can occur when resources are in short supply. RESULTS of INTERSPECIFIC COMPETITION Usually leads to one of three possible evolutionary outcomes:- • Range restriction--each species is confined to a subset of the range where it is able to out-compete the other species. Competition among species, or interspecific competition, can have an even greater effect on selection than competition within species (intraspecific competition). One possible explanation is differential susceptibility to natural enemies introduced for biological control. 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