What Alga Is?
Chlorophyll bearing organisms with thylloid
(having no True roots., stems and leaves ).
Algae has about 3000species & 2000 genera
Algae has world wide distribution from Europe -
Pacific and Asia.( Arctic, Antarctic,North& South
Occurrence & Habitat
Been recorded from snow, hot springs, tide pools to
or floating as masses of filaments or
See Weeds are mostly found in Rocky Coasts
Euglena ,Diatoms & Anabaena found in River & Ditches
Polycystis & Dinoflagellates found in Moist Places (Tree Trunks
Early reference found in Chinese Literature mentioned as TsaO
Greeks & Roman literature used words like Phycos & Fucus
Inhabitants of Hawaii used it as food known as Limu.
• Algae classification is
based on following bases.
Reserve food products
Forms of Algae (W.h.Harvay)
• Red Algae
• Brown Algae
• Green algae
Algae are Eukaryotic except Blue Green Algae.
Flagella are found in all except Cyanophyta & Rhodophyta
Three important points
Position of Flagella in primary
Classification of Algae
• Cell Wall
Made up of two materials
Inner Water Insoluble
Outer Pectic substances
Most common material of inner layer is
In cell wall of Phaephyta alaginic & Fucinic acid are found whereas
mucopeptide is present in cell wall of Blue-Green Algae.
In some algae, walls contain definite Pores for Mucilage discharge & connections
for protoplasmic connections.
Plastids & Chromatophores
• Double membrane structures are of two types
Chlorophyll a & b Chlorophyll b
Protinaceous fibrils on or in the Chromatophore surface.
One in Chlamydomonas or many in Oedogonium
Store starch in green algae
Found in all except Cyanophyta
Arise De Novo or by Division of pre-existing cells.
Golgi Bodies Mitochondria ER
G-Complex here is known as Are present Present in Most Algae
Situated near Chromatophores, Number & size vary. System of tubules.
Exact function not defined Exact function is Ribosomes on outer
so far. Respiratory related. Surface
Absent in Cyanophyta. Absent in Cyanophyta Absent in Cyanophyta.
Vacuoles Eye Spots (Stigma)
One or More Vacuoles. Orange eye-spot located
Meant for Osmotic Relation Consist of Lipid Droplets
& regulation of Solutes present irregularly.
They are light sensitive
Two Types photoreceptors.
2. Complex It helps in orientation of motile
• The various sorts of algae play significant roles in aquatic
• Provide the food base for most marine food chains
• In very high densities (so-called algal blooms) discolor the
water and out compete, asphyxiate other life forms
• Sea weeds have been recorded at depth of 300m.
• Some are used as human food or harvested for useful
substances such as agar, carrageenan, or fertilizer
Cell Chlorophyll Store light Energy
CO2 + Water (Surrounding Environment) Sugars
6CO +12H O
2 2 C H H 6O +6H O
6 12 6+ 2 2
Unicellular Cells Cell division
Filamentous forms Fragments forms Fragmentation
Blue Green Algae
Special cells types Replication of Organism
Asexual Reproduction results in development & maintenance of
Sexual reproduction involves
Union of Cells(Plasmogamy)
Union of Nuclei(Karyogamy)
Largest source of oxygen producer 83-87% of the total oxygen
Bio-diesel production .
There are also commercial uses of algae as agar
Some Cosmetics can come from micro algae as well
chemical dyes and coloring agents
Seaweeds are used as fertilisers and even food
Algae are used in wastewater treatment facilities
Algae and symbioses
lichens: A fungus is the host, usually with a green alga or a cyanobacterium as its
Corals: algae known as zooxanthellae are symbionts with corals. Notable amongst
these is the dinoflagellate Symbiodinium, found in many hard corals.
Sponges: green algae live close to the surface of some sponges, for example,
breadcrumb sponge (Halichondria panacea). The alga is thus protected from
predators; the sponge is provided with oxygen and sugars which can account for 50 to
80% of sponge growth in some species.