Prepared by :

Km. Monika Balmiki KV GANGTOK

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The study of ALGAE is called “Phycology”

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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: 1.

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Chlorophyceae Phaeophyceae Rhodophyceae

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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

VOLVOX CHLAMYDOMONAS ULVA

Chlorophyceae -Reproduction

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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 SARGASSUM DICTYOTA

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

PORPHYRA GRACILARIA 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