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27-Dec-2017 18:54

Its opposite is absolute, a term designating a quality or quantity that is independent and not defined in relation to another quality or quantity.

Amino acids exist in two forms, designated L -forms and D -forms, which are stereoisomers, or mirror images of each other.Virtually all living organisms (except some microbes) incorporate only the L-forms, but once the organism dies the L-amino acids gradually convert to D-amino acids.Several factors influence the rate of conversion, and though amino-acid racimization was popular in the 1970s, these uncertainties have led scientists to treat it with increasing disfavor.The latter, the study of Earth's physical history, is one of the two principal branches of geology, the other being physical geology, or the study of Earth's physical components and the forces that have shaped them.

The background of historical geology is discussed in some detail within the Historical Geology essay.The chronostratigraphic scale likewise has six time units, analogous to those of the geologic scale: eonothem, era them, system, series, stage, and chronozone.