Algae are usually differentiated on the basis of their pigments, flagellation and storage products. They are of 3 types; red algae (Rhodophyceae), brown algae (phaeophyceae) and green algae (chlorophyceae).
Characterstics of Algae
- Algae are chlorophyll containing thallophytes and their relatives.
- They are characterized by the absence of embryo stage and the presence of non-jackated gametangia.
- They may be unicellular, colonial, filamentous, parenchymatous or pseudoparenchymatous.
- They lack vascular tissues.
- Nutrition is photosynthetic. Grana are absent in chloroplast.
- Vegetative and asexual methods of reproduction are abundant. Asexual spores are of 2 types meiospores and mitospores.
- Sexual reproduction involves isogamy, anisogamy and oogamy in different groups.
- Life cycle could be haplontic, diplontic or haplo-diplontic.
Properties of Red Algae
- Mostly marine
- Unicellular species are fewer.
- Chlorophyll-a and d-type
- Thylakoids are unstacked.
- Fucoxanthin may be present.
- phycobilins are present.
- Cell wall contains cellulose and sulphated phycocolloids.
Properties of Brown Algae
- Mostly marine
- Unicellular species are absent.
- Chlorophyll-a and c-type
- Thylakoids occur in group of 3
- Fucoxanthin is abundant.
- Phycobilins are absent.
- Cell wall contains cellulose and non-sulphated phycocolloids.
Properties of Green Algae
- Mostly freshwater and subaerial.
- Unicellular species are abundant.
- Chlorophyll-a and b-type.
- Thylakoids are stacked in groups of 2-20.
- Fucoxanthin is absent.
- phycobilins is absent.
- Cell wall is of cellulose.