TITLE:  Where Have All the Algae Gone, Or, How Many Kingdoms are 
               There?
      AUTHOR:  BLACKWELL, WILL H.; POWELL, MARTHA J.
     JOURNAL:  American Biology Teacher
    CITATION:  March, 1995, 5793: 160-167.
        YEAR:  1995
    PUB TYPE:  Article
 IDENTIFIERS:  ALGAE; CLASSIFICATION SYSTEMS; TAXONOMY; UNICELLED 
               ORGANISMS/ALGAE
    ABSTRACT:       The meaning of the concept of biodiversity has become 
               publicly slanted towards the members of the plant and animal 
               kingdoms, especially endangered species, with little 
               attention paid to the kingdoms of bacteria, fungi, and 
               protista. Since bacteria, fungi, and protista are often 
               lumped together as microorganisms, it is microbiology that 
               has not received its share of attention. Taxonomists are not 
               as aware as they should be of microbiological diversity. 
               Microbiologists have focused more on the bacteria 
               (prokaryotes) and less on the eukaryotic microbiology--the 
               fungi and protista (including types of algae). Although there 
               is economic and biological interest in algae, their taxonomy 
               is in disarray, as evidenced by discrepancies in college 
               textbooks.
                    Certain organisms, such as Euglena, have always been 
               hard to categorize as plant or animal. Some of these 
               organisms contain chlorophyll, but a number have the 
               appearance and behavior of Protozoa. Euglena and related 
               organisms formed the core of the concept of the kingdom 
               Protista, proposed in 1866, and the earlier Protoctista, 
               which was a catch-all for unicellular organisms. The problem 
               has not been resolved; physiologists claim them as algae but 
               protozoologists claim them also. The dinoflagellates are in a 
               similar position.
                    Living organisms currently are divided into from five to 
               eight kingdoms, depending on the classification schema 
               followed. Some extreme classifications propose use of a 
               single kingdom, others have proposed up to nineteen. One 1974 
               classification, proposes seven kingdoms. These are Monera or 
               Prokaryotes (Eubacteria, including Cyanobacteria and 
               Archaebacteria). The Protozoa (unicellular and often motile 
               eukaryotes) are a diverse assemblage. Stramenophiles (the 
               chromistan assemblage) include a variety of chromophytous 
               algae and certain groups which more resemble protozoans. The 
               Animalia (Metazoa, sponges, and Placozoa) are all 
               multicellular (generally tissue level) animals. The Fungi 
               (Basidiomycetes, Ascomycetes, Zygomycetes and 
               Chytridiomycetes), now includes the true fungi. The remaining 
               kingdoms are Plantae (green plants and green algae) and 
               Biliphyta (rhodophytes and glaucophytes).
                    The algae are distributed over five of the seven 
               kingdoms. The Monera contain the "blue-green algae," or 
               Cyanobacteria, which are prokaryotic and closely related to 
               Eubacteria, but possess phycobilin pigment and chlorophyll. 
               Protozoan algal groups include the Euglenoids, 
               Dinoflagellates, and Cryptomonads. Stramenophiles include the 
               golden algae, yellow-green algae, brown algae, haptophytes, 
               and diatoms, along with other chromophytous algae. In the 
               Plantae are the grass-green algae such as Chlamydomonas, 
               Volvox, Ulothrix, Ulva, Spriogyra, Desmids, Cladophora, 
               Chara, and others. These are interpreted as being in the 
               lineages leading to higher plants. Included in the Biliphyta 
               are the red algae and possibly the Glaucophytes.
                    Endosymbiosis, or the inclusion and maintenance of a 
               cell or cell contents of one kind of organism within the cell 
               of another organism, has played a vital role in the evolution 
               of algae. It was probably responsible for the major lineages 
               of algae observed today. Algae belong to one of the following 
               three phylogenetic lineages: the blue-green lineage; the red 
               algal lineage; and the chromophyte lineage. Each line belongs 
               to a different kingdom.
                    The organisms known traditionally as "algae" are now 
               understood to be a polyphyletic assemblage. The situation is 
               similar to that of the fungi, currently also spread over 
               three kingdoms. The concept of "algae" is still viable when 
               used in reference to an ecosystem, such as an aquatic food 
               web. Various types of "algae" may have a similar appearance, 
               occur together, and play a similar eco-physiological role. 
               Thus the term "algal way of life" may be used for a variety 
               of algal-like organisms, such as those found within the 
               "bloom" of a freshwater pond.
                    "Algae" will and should persist as a form/function 
               grouping in ecological context but not as a formal 
               taxonomic/phylogenetic category. When they are taxonomically 
               divided between several kingdoms and chapters in textbooks, 
               they should be cross-referenced between coverages to aid 
               students.