Page 19 - Algae

2 Algae: Anatomy, Biochemistry, and Biotechnology

CLASSIFICATION

No easily definable classification system acceptable to all exists for algae because taxonomy is
under constant and rapid revision at all levels following every day new genetic and ultrastructural
evidence. Keeping in mind that the polyphyletic nature of the algal group is somewhat inconsistent
with traditional taxonomic groupings, though they are still useful to define the general character and
level of organization, and the fact that taxonomic opinion may change as information accumulates,
a tentative scheme of classification is adopted mainly based on the work of Van Den Hoek et al.
(1995) and compared with the classifications of Bold and Wynne (1978), Margulis et al. (1990),
Graham and Wilcox (2000), and South and Whittick (1987). Prokaryotic members of this assem-
blage are grouped into two divisions: Cyanophyta and Prochlorophyta, whereas eukaryotic
members are grouped into nine divisions: Glaucophyta, Rhodophyta, Heterokontophyta, Hapto-
phyta, Cryptophyta, Dinophyta, Euglenophyta, Chlorarachniophyta, and Chlorophyta (Table 1.1).

TABLE 1.1
Classification Scheme of the Different Algal Groups

Kingdom Division Class
Prokaryota eubacteria Cyanophyta Cyanophyceae
Prochlorophyta Prochlorophyceae
Glaucophyta Glaucophyceae
Rhodophyta Bangiophyceae
Florideophyceae
Heterokontophyta Chrysophyceae
Xanthophyceae
Eustigmatophyceae
Bacillariophyceae
Raphidophyceae
Dictyochophyceae
Phaeophyceae
Haptophyta Haptophyceae
Cryptophyta Cryptophyceae
Eukaryota Dinophyta Dinophyceae
Euglenophyta Euglenophyceae
Chlorarachniophyta Chlorarachniophyceae
Chlorophyta Prasinophyceae
Chlorophyceae
Ulvophyceae
Cladophorophyceae
Bryopsidophyceae
Zygnematophyceae
Trentepohliophyceae
Klebsormidiophyceæ
Charophyceae
Dasycladophyceae

OCCURRENCE AND DISTRIBUTION

Algae can be aquatic or subaerial, when they are exposed to the atmosphere rather than being sub-
merged in water. Aquatic algae are found almost anywhere from freshwater spring to salt lakes,
with tolerance for a broad range of pH, temperature, turbidity, and O 2 and CO 2 concentration.