Biotic environment

The hypothesis that our biological world built on the DNA-RNA-protein central dogma was preceded by an RNA world in which RNA molecules carried both the genetic information and executed the gene functions (through ribozyme activity) is now widely accepted [130]. However, it is also well recognized that RNA due to its vulnerability to hydrolysis - especially as a result of catalysis by divalent metal ions - would not have been able to evolve in a harsh pre-biotic environment Also the formation of RNA under presumed pre-biotic conditions is extremely inefficient It is not so far-fetched to propose that a peptide nucleic acid-like molecule may have been able to function as a form of pre-biotic genetic material since it... 

The most important and most particular biological activity is that by microorganisms which concentrate by preference on surface stones and rocks, where they are called lithophytes. The number of these micro-biota in various deserts throughout the world is in the order of 103 to 106 per gram of soil, and in the Sahara alone French microbiologists have described more than 45 types of cyanophyceae, 70 chlorophyceae, 90 lichens and more than 300 diatoms. Hence, deserts cannot be considered an a-biotic environment. 

In addition to the constitutive production of food supplements, some plants can actively adjust their food provision in response to their biotic environment (Table 2.2). Unlike other defense mechanisms, this induction can be elicited by two distinct mechanisms. Food provision can be raised both by food removal (Risch and Rickson, 1981 Koptur, 1992 Heil el al., 2000) and by tissue damage (Koptur, 1989 Wackers and Wunderlin, 1999 Heil et al, 2001 Wackers el al., 2001). These mechanisms represent active responses by the plants to both ant attendance and herbivore feeding. This receptiveness toward the presence of both the second and the third trophic level represents a unique and highly dynamic type of plant response. 

Degradation Product Patterns in Abiotic and Biotic Environments... 

Harvell, C.D., Complex biotic environments, coloniality, and heritable variation for inducible defenses, in The Ecology and Evolution of Inducible Defenses, Tollrian, R. and Harvell, C.D., Eds., Princeton University Press, Princeton, NJ, 1999, 231. 

Abstract. This paper reviews the degradation behavior of aliphatic polyesters of current interest, including polylactide, polycaprolactone, poly(3-hydroxybutyrate) and their copolymers. Special focus is given to degradation products formed in different abiotic and biotic environments. The influence of processing and processing additives on the properties and degradation behavior is also briefly discussed. 

Given the bacterial populations that utilized p-coumaric acid as a sole carbon source and the physicochemical (e.g., constant temperature, adequate nutrition and moisture) and biotic conditions of these two laboratory systems, utilization of p-coumaric acid ranged from 0.6 to 5.0 pg/g soil/h for the open systems and 8.6 pg/g soil/h for the closed system. The pg values for the open system represent steady-state rates as modified by nutrition, while the pg values for the closed system represent maximum rates. Whether such rates ever occur in field soils is not known, since the physicochemical and biotic environments of field soils are so different from those of laboratory systems. Laboratory soil systems provide potential rates of utilizations, but until field rates are determined the importance of microbial activity in phenolic acid depletion from soil solutions will not be known. 

The knowledge of ecotoxicology of chlorinated aromatic compounds has increased substantially over the last 10 years. In particular, observations in wildlife have shown that, contrary to what is believed now for humans, certain PCBs, PCDDs and PCDFs are causing harmful effects to individuals and populations, despite the fact that their concentrations in both the abiotic and the biotic environment have been declining continuously since the 1970s. 

Insects, pathogens, and weeds respond to their physical and biotic environment in predictable ways. For instance, growth of many fungal pathogens varies with temperature in a well-established manner. Growth starts low, increases to a maximum at the optimal temperature and then declines to zero (Fig. 2). In fact, most plant pests will respond to temperature in a similar manner. Fungal pathogens often require free moisture for infection to occur infection increases with increased time of wetness (Fig. 2). The duration of free moisture is dependent on temperature (Fig. 2), as well as other physical factors. 

Figure 5.10 Effect of typical biotic environments on polymer bioassimilation...

One of the main features of OCP spectra, especially when applied to biotic environments, are the fluctuations observed in the OCP pattern. An example can be seen in Figure 4.13. One should bear in mind that while the shape of the OCP fluctuations may vary, it is always the fluctuations that are there to characterize rather instant polarization changes. 

As can be seen, the corrosion rates (as measured by corrosion current density) in biotic cases show an increase in comparison with the abiotic environment. Also, it can be seen from the SEM micrographs that while in abiotic environment the oxide layer on carbon steel is almost intact, it has been cracked and pitted (Figure 4.24c) in the biotic environments. These findings may strongly suggest that lOB are indeed very corrosive and thus must be taken care of when they exist in a system. 

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