Classification, taxonomy chemical

As seen in Figure 6.3, the taxonomy used for chondrites is a combination of chemical group and petrologic type, as in H4 or 2. This system avoids the problems of previous chondrite classifications, by cleanly separating primary and secondary characteristics. 

The classification of plants is primarily based on the similarities and differences that are displayed by their morphological and anatomical characteristics. In some instances this does not suffice since the morphological differences may not be genetically defined but have been caused by local bio-climatic factors. Nevertheless is apparent that secondary metabolites can contribute to the taxonomy of plants and their systematic evolution. There are many examples of cases where the morphological features are not clear and secondary metabolites serve to clarify the morphological classification (e.g. classification of the tribes of the family Asteraceae). It has also been proved to be significant to use all the secondary metabolites for the above purpose and not only one of their chemical groups [4]. 

McFarlane, 1976, 1983a), through to mineralogical and textural based schemes (e.g. Aleva, 1986 Bardossy and Aleva, 1990), to a system incorporated within soil taxonomy (Soil Survey Staff, 1975), as well as more quantitative, chemically based genetic classifications (Schellmann, 1982). It is not the intention of this chapter to discuss the merits of these schemes, nor to outline the others that have been proposed this has been reviewed previously (e.g. McFarlane, 1976, 1983a Aleva, 1994 Bourman and Ollier, 2002). Instead, a simple distinction is made between laterite and ferricrete (Aleva, 1994), and a chemical classification for defining lateritic materials (Schellmann, 1982, 1986) is adopted. 

Individual secondary metabolites may be common to a number of species or may be produced by only one organism. Related species often have related patterns of secondary metabolite production and so a species can be classified according to the secondary metabolites they produce. Such a classification is known as chemical taxonomy. Occasionally, two plants are found to have identical physical aspects which botanists use for classification, but differ in the secondary metabolites they produce. For example, two flowers may look identical but one is odourless whilst the other possesses a strong scent due to the production of a fragrant terpenoid chemical. Such different strains are known as chemotypes. 

Taxonomy itself has broadened. Many systematists regard living organisms as complexes of physico-chemical properties rather than of static characters and at least theoretically look upon classification as an expression of all that is known about animals or plants, whether derived from anatomy, physiology, ecology, genetics, chemistry, et al. ... 

Only a few remarks can be made here on the classification of biological materials. Chemical taxonomy C2933 tries to characterize biological individuals chemical compounds found in several parts of the individual. Pattern recognition might be a useful technique to handle these data C343H. 

Hegnauer, R., Chemical characters and the classification of the Rutales, in Chemistry and Chemical Taxonomy of the Rutales (P. G. Waterman and M. F. Grundon, eds.). Annual Proceedings Phytochemistry Society of Europe 22), 401-440, Academic Press, London, 1983. 

The s)Tstematic classification of minerals according to the American Chemist and Mineralogist James Dwight Dana was the first to be established in 1837 using the Linnaen principles of taxonomy modified by Friedrich Mohs and the Berzelius system for the notation of chemical formulae. Since 1837, it was modernized to take into account recent discoveries. 

Apart from the fact that the majority of lichens can be categorized as either basidiolichens or ascolichens, and the numerous sterile species that have obvious affinity with the latter, lichen taxonomy is very much an arbitrary system. Classifications so far developed are artificial and based, to a large extent, on seemingly constant morphological characteristics or more recently on chemical constituents (Culberson and Culberson, 1970" It is... 

The third goal was to compare the distribution of diterpenes to the classification scheme used to subdivide the Compositae into its subfamilies, tribes, subtribes, genera, etc., and to seek chemical distribution patterns that paralleled the plant taxonomic boundaries. As diterpenes constitute a substantial body of raw taxonomic data, they may hold some promise as novel characters for use in plant taxonomy. 

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