High interspecific variation

Individual mitochondrial enzymes such as the lipid-requiring enzyme cytochrome C oxidase exhibit interspecific variation in ABTs similar to that seen for mitochondrial oxygen consumption (O Brien et al., 1991 Dahlhoff and Somero, 1993b). Thus, the impairment of mitochondrial respiration at high temperatures may be due to loss of activity of enzymes in ATP-generating pathways. 

Glucosinolates in most craciferous crops and model plants show high levels of interspecific variation in both stracture and content due... 

The hydrolysis of esters by esterases and of amides by amidases constitutes one of the most common enzymatic reactions of xenobiotics in humans and other animal species. Because both the number of enzymes involved in hydrolytic attack and the number of substrates for them is large, it is not surprising to observe interspecific differences in the disposition of xenobiotics due to variations in these enzymes. In mammals the presence of carboxylesterase that hydrolyzes malathion but is generally absent in insects explains the remarkable selectivity of this insecticide. As with esters, wide differences exist between species in the rates of hydrolysis of various amides in vivo. Fluoracetamide is less toxic to mice than to the American cockroach. This is explained by the faster release of the toxic fluoroacetate in insects as compared with mice. The insecticide dimethoate is susceptible to the attack of both esterases and amidases, yielding nontoxic products. In the rat and mouse, both reactions occur, whereas sheep liver contains only the amidases and that of guinea pig only the esterase. The relative rates of these degradative enzymes in insects are very low as compared with those of mammals, however, and this correlates well with the high selectivity of dimethoate. 

The spatial-variation-in-consumers model (SVICM) was proposed by marine ecologists to explain both interspecific and intraspecific patterns of chemical defenses in seaweeds.111 It states that chemically defended seaweeds will be more evolutionarily persistent than undefended seaweeds in areas subject to significant herbivore impact. Likewise, this model explains intraspecifc variation in chemical defenses, in that well-defended individuals or populations will be more persistent over ecological time scales than undefended seaweeds in areas subject to significant herbivore impact. This model borrows heavily from the optimal defense theory, in that it suggests that seaweeds that occur in areas with high herbivory pressure will be vulnerable to herbivore attack and should thus be heavily defended. 

Third, dispute exists over whether there even is a universal scaling relation and whether ostensible patterns reflect internal biophysical constraints of any kind (Clarke, 2004 Clarke and Fraser, 2004 Kozlowski, 1996 Kozlowski and Weiner, 1997 Kozlowski and Konarzewski, 2004). This is asserted for two reasons. For one thing, it is claimed that the data do not support the model. This is because the 3/4 rule itself is an artifact of an interspecific regression that traverses heterogeneous intraspecific regressions with independent slopes and intercepts and also because functionalist explanations do not adequately accoimt for the extremely large and highly correlated residual variation (Kozlowski and Weiner, 1997). ... 

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