by :Piya Roychaudhuri For 1st semester ALGAE by :Piya Roychaudhuri For 1st semester

The study of ALGAE is called “Phycology” Chlorophyl- bearing plants, Thalloid , Autotrophic & Aquatic.

HABITATS A)Aquatic ( Fresh water & marine) Moist stones, Soils and Wood. B) Association with Fungi e.g. Lichen and animals e.g. Sloth bear C) Marine forms are Sea Weeds D) Fresh water Algae – Microscopic, Unicellular e.g. Chlamydomonas - Colonial forms e.g. Volvox - Filamentous forms e.g. Ulothrix & Spirogyra.

REPRODUCTION Vegetative – by fragmentation. Fragments develops into thallus. Asexual - produce different type of spores (zoospores) - Zoospores – Flagellated motile and germination gives rise to new plants.

Sexual Reproduction – fusion of two gemets 1. Isogamous – Flagellated similar in size e.g. chlamydomonas - Non-flagellated but similar in size e.g. spirogyra. 2. Anisogamous – two gemets dissimilar in size e.g. chlamydomonas. 3. Oogamous - Fusion between one large, non-motile – female gemete. smaller motile- male gamete e.g. Volvox, Fucus.

Isogamous Anisogamous Oogamous

CLASSES OF ALGAE The Algae are divided into three mail Classes: Chlorophyceae Phaeophyceae Rhodophyceae

CHLOROPHYCEAE ( Green Algae) Plant Body - unicellular, Colonial or Filamentous Rigid Cell Wall – Inner layer – Cellulose - Outer layer – Pectose Green due to chlorophyll a & b Definite chloroplasts – Discoid, Plate-like reticulate, cup- shaped,spiral or ribbon-shaped Storage bodies - Pyrenoids, located in the chloroplasts. Store food in the form of oil droplets

CHLAMYDOMONAS VOLVOX ULVA

Chlorophyceae -Reproduction The Sex organs are always unicellular Vegetative – Fragmentation(spores) Asexual Reproduction – Flagellated zoospores Sexual Reproducion – isogemous, anisogemous and oogamous

Phaeophyceae (Brown Algae) Marine habitats Plant body attached to the substratum by a Hold fast, Stalk –Stipe, Leaf Like- Photosynthetic organ – Frond Golden brown – Xanthophyll pigment fucoxanthin in their chromotophores. Addition to chlo.a, chlo.c and carotenoids. Accumulation of reserve food as fats and oil rather then starch. The cellulosic wall covered by algin Centrally located vacuole and nucleus.

LAMINARIA DICTYOTA SARGASSUM

Phaeophyceae- Reproduction Vegetative reproduction – Fragmentation Asexual Reproduction - biflagellate zoozpores (two unequal) Sexual Reproduction - Isogamous, anisogamous or oogamous. - Union of gamets takes place in water or within the oogonium.

Rhodophyceae (Red Algae) Red Pigment, r-phycoerythrin in their body Found in the warmer areas Red thalli – Multicellular The food stored as floridden starch

GRACILARIA PORPHYRA GELIDIUM

Rhodophyceae-Reproduction Vegetative Reproduction – Fragmentation Asexual – Non-motile spores Sexual - Non-motile gamets (oogamous) e.g. Polysiphonia, porphyra etc.

Algae- Economic Importance Use as Food e.g. Porphyra, Laminaria & Sargassum. Certain marine brown & red algae produce large amount of hydrocolloids (water holding substances) Algin – brown algae e.g. sargassum Agar used to grow microbs and preparation of icecream and jellies e.g. Gelidium & Gracilaria. Rich proteins – Chlorella & Spirullina

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