Phylogenetics and Occurrence
The purpose of this section is to examine the extent to which there is a correlation between lipid biochemistry and organismic affinities deduced by taxonomy, in the hope of tracing familial lines (phylogenetics). Implicit in the discussion is the tentative assumption that the manner in which a cell handles lipids is a phenotypic expression of the genotype and that it is the genotype we wish to trace. Certain biochemical characteristics seem to be common to all organisms. All, for instance, seem to have ATP. This is a fairly large and complex molecule, yet apparently all cells biosynthesize it either de novo or from ingested parts, e.g., nicotinamide, and do not vary its structure to the exclusion of ATP itself. Such is not the case with many other molecules that as a class may be present or wholly absent or may be present but in limited and organismically varied form. These molecules would seem to be appropriate as phylogenetic markers, and many are lipids. We will first review the structural aspects and then examine biosynthesis, etc. The large amount of information now available forces us to restrict ourselves in a chapter such as this only to some of the more salient features of the subject. Instead of taking organisms one by one and summarizing their lipids, or conversely, taking molecular classes one by one and reviewing the organisms they occur in, we will ask and attempt to answer some direct questions about familial relationships.
KeywordsFatty Alcohol Slime Mold Fatty Acid Pattern Eukaryotic Alga Vertebrate Line
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