Classification of Algae

Posted on 18/08/2011 by Chimithen  

 

Classification of Algae

The classification of algae into taxonomic groups is based upon the  same rules that are used for the classification of land plants, but the  organization of groups of algae above the order level has changed  substantially since 1960. Research using electron microscopes has  demonstrated differences in features, such as the flagellar apparatus,  cell division process, and organelle structure and function, that are  important in the classification of algae. Similarities and differences  among algal, fungal, and protozoan groups have led scientists to propose  major taxonomic changes, and these changes are continuing.

Division-level  classification, as with kingdom-level classification, is tenuous for  algae. For example, some phycologists place the classes  Bacillariophyceae, Phaeophyceae, and Xanthophyceae in the division  Chromophyta, whereas others place each class in separate divisions:  Bacillariophyta, Phaeophyta, and Xanthophyta. Yet, almost all  phycologists agree on the definition of the respective classes  Bacillariophyceae, Phaeophyceae, and Xanthophyceae.

The classes are distinguished by the structure of  flagellate cells (e.g., scales, angle of flagellar insertion,  microtubular roots, and striated roots), the nuclear division process  (mitosis), the cytoplasmic division process (cytokinesis), and the cell  covering. Many scientists combine the Micromonadophyceae with the  Pleurastrophyceae, naming the combined group the Prasinophyceae.  “Phylum” and “division” represent the same level of  organization; the former is the zoological term, the latter is the  botanical term

Properties of Major Algal Taxonomic Groups

S.No Taxonomic Group Chlorophyll Carotenoids Bilo

proteins

Storage products Flagellation &Cell structure
1. Bacillariophyta a, c β-carotene

± -carotene  rarely fucoxanthin,.

Chrysolaminarin

oils

1 apical  flagellum in male gametes:

cell in two halves with elaborate

markings.

2. Chloro

phycophyta

(green algae)

a, b β-carotene,

± -carotene

rarely  carotene

and lycopene,

lutein.

Starch, oils 1,2,4 to many,

equal, apical  or

subapical flagella.

3. Chrysophycophyta

(golden algae)

a, c , β-carotene,

fucoxanthin

Chrysolaminarin

oils

1 or 2 unequal, apical flagella, in some, cell  surface covered by characteristic scales.
4. Cyanobacteria

(blue green algae)

a,c β-carotene,

phycobilins

5. Phaeco

phycophyta

(brown algae)

a,c β-carotene, ±

fucoxanthin,

violaxanthin

Laminarin, soluble

carbohydrates,  oils

2 lateral flagella
6. Dinophyta

(dinpflagellates)

a,c β-carotene,

peridinin,

neoperididnin

dinoxanthin,

neodinoxanthin.

Starch, oils 2 lateral, 1 trailing,1 girdling flagellum, in  most, there

is a longitudinal

and transverse

furrow and angular plates.

7. Rhodo

phycophyta

(red algae )

a, rarely d β-carotene, zeaxanthin

± β  carotene

Phyco

erythrin

phyco

cyanin

Floridean starch

oils

Flagella absent

 

Comments are closed.