The term Algae (L. alga- sea weed) is collectively used for all the Chlorophyll bearing nonvascular thalloid organisms.
Linnaeus (1754) first coined the term algae, which he placed along with Liverworts & lichen under class Cryptogamia of Conventional Plant-Kingdom.
But, in Whittaker’s classification, all members of algae are redistributed in three kingdoms i.e. Monera (Blue Green Algae), Protista (Diatoms, Dinoflagellates, Euglenoids) & Plantae (Greenlagae, Brown algae & Red algae).
The study of algae is called Phycology or Algology. F.E. Fritsch is known as ‘Father of algology’ and, his student M.O.P. lyenger from Madras University is known as the ‘father of Modern Algology of India’. His important contribution is discovery of heterotrichous terrestrial alga (Fritschiellatuberosa).
1. Algae include a group of about of 30,000 species which are generally aquatic (both freshwater & marine).
2. Their size varies from microscopic forms to the filamentous forms.
3. All the members of algae are Chlorophyllus, non-vascular thallophytes.
4. They contain chlorophyll a, carotenes and xanthophylls. Additional pigments occur in specific groups.
5. Mucilage protects algal thallus from desiccation and from epiphytic growth. G. Vascular & mechanical tissues absent.
7. Vegetative and asexual modes of reproduction are very common. Asexual spores are of two types: mitospores and meiospores. They are easily dispersed in aquatic habitat, actively, if motile and passively by water currents, if non-motile.
8. Sex organs are non jacketed.
9. Sexual reproduction usually occurs towards the end of growing season.
10. Embryonic stage absent which is a characteristic feature of thallophyta.
11. Sexual reproduction involves isogamy, anisogamy and oogamy in different groups.
12. Different types of life cycle occur, viz., Haplontic (haploid phase dominant), Diplontic (diploid phase dominant) and Haplodiplontic (both haploid and diploid phase equally dominant).