1. All organisms are identified by a two-word Latin name (binomial);
many also have one to numerous common names. Biologists recognized the need
for worldwide uniformity in naming and classifying organisms. 2. Theophrastus first classified plants in the 4th century b.c. Monocots
and dicots were distinguished in the 13th century; herbalists later added many
plants to Theophrastus's original list. Descriptive Latin phrase names were
used for all organisms by the 18th century. 3. Linnaeus compiled a comprehensive list of all known Latin phrase
names for plants according to their genera in Species Plantarum, published
in 1753. Linnaeus placed specific kinds of related organisms (species) in each
genus; he also listed a single word next to the Latin phrase, which, when combined
with the name of the genus, formed an abbreviation for each species. 4. The abbreviated binomial, plus the authority for it, eventually replaced
the phrase name; this method of naming plants became known as the Binomial System
of Nomenclature. Linnaeus organized all known plants into 24 classes, based
primarily on the number of stamens in flowers. 5. At a meeting in Paris in 1867, European and American botanists agreed
to use Linnaeus's 1753 publication and binomials as the starting point for all
scientific names of plants. The rules (International Code of Botanical Nomenclature)
drawn up at that meeting and periodically revised are now followed for naming
and classifying plants by botanists of all nationalities. 6. At first, two kingdoms (Plant and Animal) were recognized. Hogg and
Haeckel proposed a third kingdom (Protoctista) in the 1860s. In 1938, H. F.
Copeland, on the basis of cellular differences, divided the Protoctista into
Kingdoms Monera and Protoctista. 7. In 1969, Whittaker proposed five kingdoms based both on forms of
nutrition and cellular structure. In the 1980s, Carl Woese divided Whittaker's
Kingdom Monera into two kingdoms, and six kingdoms are now generally recognized. 8. Since Linnaeus's time, several classifications have been added between
the level of kingdom and genus. 9. The second part of a binomial, the specific epithet, is followed
by the name of the author, usually in abbreviated form. 10. Subcategories (e.g., subspecies, suborder) are sometimes used in
classification. 11. Taxonomists construct keys to aid in the identification of organisms.
Most keys are dichotomous. Keys to major groups of organisms deal only in generalities
and do not always indicate occasional exceptions or allow for intermediate forms
that may be transferred back and forth between groups as new knowledge about
them is gained. 12. Cladistics is a system of classifying and inferring evolutionary
relationships based on an examination of shared features and differences. | 
2003 McGraw-Hill Higher Education