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Algae – Definition, Habitat, Characteristics, Types

Short Notes on Algae

ALGAE Definition: Algae is a chlorophyll-bearing, simple, thalloid, autotrophic and largely aquatic organism

Habitats: Naturally occur in moist stones, soils and wood

occur in association with 
fungi – lichen
animals – sloth bear

Form and size – highly variable


  • Vegetative reproduction – fragmentation.
  • Asexual reproduction – different types of spores, common – zoospores
  • Sexual reproduction – fusion of two gametes.


  • unicellular – Chlamydomonas
  • colonial form – Volvox
  • filamentous – Ulothrix and Spirogyra.
  • massive plant bodies – kelps


  • isogamous flagellated and similar in size 
  • non-flagellated and similar in size – Spirogyra
  • anisogamous
  • gametes dissimilar in size 
  • oogamous – Volvox, Fucus


  • half of the total carbon dioxide fixation on earth is carried by algae
  • increase the level of dissolved oxygen in their immediate environment
  • paramount importance as primary producers of energy-rich compounds
  • Porphyra, Laminaria and Sargassum and 70 species of marine algae are used as food.
  • algin (brown algae) and carrageen (red algae) produce large amounts of hydrocolloids 
  • Gelidium and Gracilaria are used to grow microbes and in preparations of ice-creams and jellies
  • Chlorella rich in proteins is used as food supplement even by space travellers