Explain how the Linnaean system of classification, although developed without any concept of
evolutionary theory, provided a reasonable, if not perfect, framework for later application of
evolutionary systematics. What limitations of the Linnaean system have spurred cladists to argue for
its abandonment and replacement by modern cladistic approaches?
What will be an ideal response?
The Linnaean system was based on morphological descriptions, which provide a reasonable basis for
sketching out a logical hierarchy for grouping organisms. The hierarchical system is still applied to
cladistic approaches, in that more ancestral forms link groups deeper in a cladogram, and thus
represent a more inclusive (or higher on the hierarchical framework) grouping or clade. While
Linnaeus did not envision a historical sequence of ancestral and descendant relationships, as did
Darwin, the increasingly inclusive groupings of genus, family, order, class, phylum, and kingdom can
capture the essence of shallower and deeper evolutionary divergences. The limitations of this approach
are that the morphological data can provide numerous ways of grouping taxa, which may or may not
accurately reflect the historical divergences, as can now be understood more fully with genetic data
and with more complete fossil data (for example, Class Reptilia). The Linnaean classifications
contained, in retrospect, many polyphyletic and paraphyletic taxa, which cladists do not allow.
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