Pidwirny, M. (2006). "Biological Classification of Organisms". Fundamentals of Physical Geography, 2nd Edition. Date Viewed. http://www.physicalgeography.net/fundamentals/9b.html

CHAPTER 9: Introduction to the Biosphere

(b). Biological Classification of Organisms

The term species has its origins in the ancient Latin language. In this language, the word species means kind. A more technical definition of species is a group of interbreeding organisms that do not ordinarily breed with members of other groups. Biologists estimate that about 10 to 40 million different species inhabit the Earth. Of these species, approximately 1.5 million have been classified.

The first individual to propose an orderly system for classifying the variety of organisms found on our planet was Linnaeus (1753). In his system of classification, the finest unit in the organization of life is the species. Linnaeus suggested that every organism should be classified with a unique binomial name. The first term in this classification system is the organism's generic name or Genus. The second term is the organism's specific name or species designation.

Current classification systems have developed from Linnaeus' original work. However, modern classification systems are much more complicated having many levels of hierarchical organization. These systems are also taxonomic (structural and physiological connections between organisms), phylogenic (classification based on genetic connections between organisms), and are structurally based on Darwin's theory of evolution.

Modern classifications of organisms are standardized in a hierarchical system that go from general to specific. Table 9b-1 below describes the detailed classification of the tree red maple. Note that each level of organization is based on some biological characteristic that the organism possesses.

Table 9b-1: Hierarchical system of the biological classification of an organism.

 Category                 Name                       Characteristics

 Kingdom                Plantae     Organisms that usually have rigid                                                   cell  walls and usually possess                                                                          chlorophyll.

 Subkingdom     Embryophyta           Plants forming embryos.

 Phylum             Tracheophyta                Vascular plants.

 Subphylum       Pterophytina       Generally large, conspicuous                                                             leaves, complex vascular                                                                             system.

 Class              Angiospermae   Flowering plants, seed enclosed                                                                          in  ovary.

 Subclass       Dicotyledoneae        Embryo with two seed leaves.

 Order               Sapindales         Soapberry order consisting of a                                                               number of trees and                                                                                  shrubs.

 Family             Aceraceae                       Maple family.

 Genus                 Acer                        Maples and box elder.

 Species          Acer rubrum                       Red maple.

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