Algae are a diverse group of photosynthetic organisms that live in both aquatic and terrestrial environments. They can be unicellular, like Chlorella, or multicellular, like red algae. Algae reproduce through vegetative, asexual, and sexual means. They are classified based on characteristics like pigmentation, food storage, and reproduction methods. The major groups of algae include green algae, red algae, golden algae, blue-green algae, diatoms, and brown algae.

1. Important features of Algae
BY
Harinatha Reddy Aswartha

2.  Algae eukaryotic photosynthetic organisms.
 Photoautotrophs.
 Unicellular (Chlorella and diatoms) and multicellular (Red
algae, green algae).
 An undifferentiated plant body is known as thallus.
 In thalloid plants, there is no differentiation of plant body
into true roots, stem and leaves.

3.  Majority of algae are in aquatic habitat (fresh water or
marine), some algae are terrestrial.
 Cell wall made up of cellulose and it also contain
hemicellulose, silica, pectin.

4.  Membrane enclosed organelles are present.
 Chloroplast is present

5. Reserved food materials in algae:
 Starch and oils.

6. Pigments:
 All major algal groups have at least one characteristic pigment:
 Cyanophyceae (blue green algae): Phycocyanin.
 Chlorophyceae (green algae): Chlorophyll b.
 Pheophyceae (brown algae): Fucoxanthin.
 Rhodophyceae (red algae): Phycoerythrin .
 Chlorophyll a is universally present in all algal groups.

7. Algae reproduce by three methods:
(1).Vegetative reproduction:
 Fragmentation, binary fission and buddings etc. are the
important vegetative reproduction methods in algae.
(2). Asexual reproduction:
 By a variety of motile or non-motile spores.
 Zoospore, aplanospore, tetraspore, autospore etc.
(3). Sexual reproduction:
 The union of gametes are involved: Autogamy, isogamy,
anisogamy and oogamy are the different types of sexual
reproduction algae.

8. Classification of algae:
 F.E. Fritsch (1935) a British biologist classified the whole
of the algae into eleven classes on the basis of type of
pigments, nature of reserve food material, mode of
reproduction etc.

9. Chlorophyceae (Green algae):
 Most forms are fresh water and a few are marine.
 Pigments: Chief pigments are chlorophyll a, b and beta
carotenoids.
 Reserve food: Starch
 Reproduction:
 Asexual reproduction is by zoospores.
 Sexual reproduction ranges from isogamous to advanced
oogamous type.
 Example: Chlamydomonas, Volvox, Chlorella.

10. Class: Rhodophyceae (Red algae):
 Occurrence: Few forms are fresh water and others are marine.
 Pigments: Chromatophores contain phycoerythrin, Chl-a,d,
and alpha, beta carotenes.
 Reserve food: Starch.
 Structure: Simple filamentous.
 Reproduction: Asexual by tetra spores non motile.
 Sexual reproduction is Advance oogamous type.
 Example: Polysiphonia

11. Xanthophyceae (Yellow-green algae):
 Occurrence: Most forms are fresh water but a few are marine.
 Pigments: Chlorophyll a and c, β-carotene, Yellow xanthophyll is
found abundantly.
 Structure: Unicellular motile to simple filamentous.
 Reserve food: oils and polysaccharides
 Reproduction: Sexual reproduction is rare and always isogamous.
 Asexual:zoospores and aplanospore.
 Example: Vaucheria

12. Class: Myxophyceae (Cyanophyceae or Blue green algae):
 Occurrence: Found in sea and fresh water.
 Pigments: Chlorophyll a and b, beta carotenes, xanthophylls, and
phycocyanin and phycoerythrin.
 Reserve food: Sugars and Glycogen.
 Structure: Simple type of cell to filamentous.
 Reproduction: Asexual binary fission.
 There is no sexual reproduction.
 Example: Nostoc

13. Bacillariophyceae (Diatoms):
 Diatoms are a major group of algae, the most common types
of phytoplankton.
 Diatoms are unicellular.
 Pigments: Chl a and c, Chromatophores are golden brown.
 Reserve food: Starch, oils and volutin granules.
 Cell wall composed of silica.
 Reproduction: Asexual reproduction by binary fission and
sporogenesis.
 Sexual reproduction occurs by fusion of protoplasts.
Example: Pinnularia

14. Class: Euglenineae:
 Occurrence: Only fresh water forms are known.
 Pigments: Chl a, b and Chromatophores are pure green.
 Reserve food: Polysaccharide and starch.
 Structure: No cell wall, Motile with single flagella.
 .
 Reproduction: Asexual binary fission.
 Sexual reproduction not proved definitely
 Example: Euglena
l

15. Chrysophyceae: (Golden algae):
 Occurrence: Most forms occur in cold fresh water but a few are marine.
 Pigments: The pigments are chlorophyll-a, -c and Chromatophores are
orange in colour.
 Reserve food: Oils and polysaccharides.
 Structure: Plants are unicellular, flagellated and colonial.
 Reproduction: Asexual reproduction by binary fission and sporogenesis.
 Sexual reproduction reported in some members.
Example: Prymnesium parvum

16. 5. Cryptophyceae:
 Occurrence: Both in marine and fresh water.
 Pigments: Chl a and c, Phycocyanin, Chromatophores show
diverse pigmentation.
 Reserve food: Solid carbohydrates or in some cases starch.
 Structure: Represented by motile cells, Contain two unequal
flagella.
 Reproduction: Isogamous.
 Example: Chroomonas

17. 6.Dinophyceae:
 Occurrence: Both in marine and fresh water and These are benthic.
 Reserve food: Starch and oil.
 Pigments: Chl a, b, Chromaophores are brown colour etc.
 Structure: Unicellular motile (possess two dissimilar flagella.) simple to
branched filamentous.
 Reproduction: Asexual by binary fission.
 Sexual reproduction is of isogamous type.
 Example: Dinoflagellate

18. 7. Class: Chloromonadineae (Raphidophyceae):
 Occurrence: Mostly fresh water forms.
 Pigments: Chl a and b, Chromatophores are bright green in
colour and contain an excess of xanthophyll.
 All raphidophytes are unicellular, with large cells (50 to 100
μm), but no cell walls.
 Reserve food: Oil
 Structure: Motile, biflagellate with two almost equal flagella.

19. Class 9. Phaeophyceae (Brown Algae):
 Occurrence: Mostly marine.
 Pigments: Chl a, c, Beta carotenes, xanthophylls (Fucoxanthin),
not chl b.
 Reserve food: Mannitol and fats.
 Structure: Simple filamentous to bulky parenchymatous forms.
 Reproduction: Asexual reproduction by zoospores.
 Sexual reproduction ranges isogamous to oogamous.
 Example: Ectocarpus, Sargassum