ALGAE ■ chlorophyll-bearing, simple, thalloid, autotrophic and largely aquatic ■habitats: 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. ▪︎ 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 🟦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 ● 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