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

Reproduction

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

FORM AND SIZE

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

TYPE OF GAMETE

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

USEFUL TO MANKIND

• 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