|Themes > Science > Zoological Sciences > About Zoology, Generalities > Diagram of the Modern Classification Scheme|
..Organization of our Website
..Background on Classification
..Format for Classification
To gain a working knowledge and better understanding of the methods and taxonomic and systematic basis for the classification of organisms. To observe a number of different organisms from different domains, kingdoms, phyla, and classes, and to compare and contrast these organisms and understand their evolutionary relationships.
The biological classification system uses taxa, or individual levels of organization, to classify all organisms. To navigate around this website, you can use one of the following:
*Click on any taxon (e.g. Eukarya) and you will be pointed to the page for that taxon containing a comprehensive description, any applicable diagrams, and a list of all subordinate taxa.
On the Conclusions page, there is a comprehensive essay detailing the radiation of the diversity of life as we know it, beginning at the lifeless Earth and proceeding through the evolution of humans.
The information for each kingdom refers to the questions in "Format for Classification," seen below.
Classification is essentially an effort by scientists to discover, reconstruct, and clarify the phylogeny, or evolutionary history, of an organism or group of organisms. This effort is a part of systematics, or the study of biological diversity and organization. Organisms are classified in a number of different taxa, or levels.
The number and depth of systematic taxa have changed significantly over the years. A two-kingdom system (plants and animals) was instituted in the mid-18th century by Carolus Linnaeus, who also proposed the binomial system for naming organisms (with the scientific name including the genus and species name). This system was prevalent and widely accepted for over two hundred years, but it obviously had several major problems, including the ambiguous classification of prokaryotes, protists, and fungi. In 1969, American ecologist Robert H. Whittaker instituted a five-kingdom system with Kingdoms Monera (the prokaryotes), Protista (unicellular, multicellular, and colonial protists), Plantae (the plants-multicellular photoautotrophs with cellulose cell walls and discrete organs), Fungi (multicellular non-motile chemoheterotrophs with a unique reproductive method and life cycle) and Animalia (the animals-multicellular motile chemoheterotrophs having cells lacking cell walls). This system has thrived for three decades, and indeed is still somewhat widely used.
In this lab, however, we will utilize the system now considered generally to be the best. This new system institutes a taxon above kingdom--the domain. Under the new system, life consists of three domains--Bacteria, Archaea, and Eukarya. The Bacteria and Archaea are all the prokaryotes--confined to a single kingdom under Whittaker's system. There are a number of distinctions between the two domains, which are discussed on a separate page.
These two domains are believed to have diverged very early in the evolution of life. Eukaryotes then diverged from Archaea, and they comprise the third domain, consisting of kingdoms of plants, animals, fungi, and several protist kingdoms (for simplicity in this lab, we refer to them comprehensively as Kingdom Protista). A great deal of scientific research continues to go toward discovering more about and supporting (or refuting) this system of classification.
Classic systematics utilizes a number of methods to directly derive the classification of an organism. In addition to anatomical considerations (including homologous structures), molecular biology has become a powerful tool, and contributes to systematics by providing the means for protein comparisons and analysis of DNA and RNA.
Beyond these direct classical methods, cladistic analysis has taken root rather recently (since the 1960s). It involves the use of classical methods to organize organisms into clades, or monophyletic taxa. Each clade shares a distinct feature. The study of these features in the context of an ingroup (organisms that have any of the features) and an outgroup (organisms that have none) has allowed the establishment of a number of effective classification schemes. In cladistic analysis, each feature, or character, is viewed as a primitive character (common to an entire group) or a derived character (that arose in the evolution within the group). Cladistic analysis tends to be more objective than classic analysis, and allows for testable hypotheses. Closely tied to cladistic analysis is parsimony, or the search for the simplest practical phylogeny for an organism.
Keeping this primer in mind, you will be able to better understand the basis for the classification of our organisms. For more information about classification, we have found several excellent pages with focuses similar to ours at The University of Ohio, The University of Arizona, Yahoo! Directories, and Lycos Directories.
The general procedure for the Classification Lab was as follows:
For each organism, a brief biological description is given. In addition, four main questions are answered: