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Algae introduction
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Algae are a diverse group of aquatic organisms that have the ability to conduct photosynthesis. Certain algae are familiar to most people; for instance, seaweeds (such as kelp or phytoplankton), pond scum or the algal blooms in lakes.

Algae are a diverse group of aquatic organisms that have the ability to conduct photosynthesis. Certain algae are familiar to most people; for instance, seaweeds (such as kelp or phytoplankton), pond scum or the algal blooms in lakes.


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  1. 1. ALGAE Dr. RACHANA CHOUDHARY Department of Microbiology Shri Shankaracharya Mahavidyalaya Junwani, Bhilai
  2. 2. SYNOPSIS :- •Introduction •Contribution of Indian Phycologists •General Characteristics features •Habit & Habitat •Organization of Thallus •Form & Size of Algae •Pigment Constitution of Algae •Reproduction of Algae •Classification of Algae •Economic Importance of Algae •Conclusion •References
  3. 3. INTRODUCTION Algae are a diverse group of aquatic organisms that have the ability to conduct photosynthesis. Certain algae are familiar to most people; for instance, seaweeds (such as kelp or phytoplankton), pond scum or the algal blooms in lakes.
  4. 4. Contribution of Indian Phycologists •Ghose-1919-1932 •Prof. O. P. Iyenger 1920(Father of Algae in India) •S. R. Narayan Rao 1941-49 –Indian Fossil Algae •R. Subrahmanyam (1954)-Reproduction of Diatoms •G.S. Venkataraman studied on Charophytes
  5. 5. General Characteristics features •Algae are photosynthetic organisms •They can be either unicellular or multicellular. •Algae lack a well-defined body, so, structures like roots, stems or leaves are absent •Algae are found where there is adequate moisture. •Reproduction in algae occurs in both asexual and sexual forms. • Asexual reproduction occurs by spore formation. •Algae are free-living, although some can form a symbiotic relationship.
  6. 6. Habit & Habitat 1. Aerial & Terrestrial Algae 2. Aquatic Algae Fresh Water Marine Water 3.Algae of Unusual Habitats 1. Snow Algae 2. Thermal Algae 3. Halophytic Algae 4. Lithophytic Algae 5. Epiphytic Algae 6. Aero phytic Algae 7. Symbiotic Algae 8. Parasitic Algae 9. Epizoic Algae 10. Endozoic Algae
  7. 7. Organization of Thallus 1. Motile 2. Palmelloid 3. Dendroid 4. Coccoid 5. Filamentous 6. Heterotrichous 7. Siphonaceous.
  8. 8. Form & Size of Algae •Algae have a great range of shapes and sizes, from spherical cells with 0.5 μm diameter to 60 m long multicellular thalli. •There are about 72,500 validly described species of algae; they live in the top 300 m of marine and inland waters, and on land.
  9. 9. Pigment Constitution of Algae 1.Chlorophylls: Chlorophyll a – present in all higher plants and algae Chlorophyll b – present in all higher plants and green algae Chlorophyll c – diatoms and brown algae Chlorophyll d – red algae 2.a.Carotenes: α-carotene – higher plants and most algae β-carotene – most plants & some algae b. Xanthophylls: luteol, fucoxanthol and violaxanthol 3.Phycobillins a. Phycocynin- Blue in Colour b. Phycoerythrin- Red in Colour
  10. 10. Reproduction in Algae (A) Vegetative Reproduction (B) Asexual Reproduction (C ) Sexual Reproduction
  11. 11. (A) Vegetative Reproduction (i) Fragmentation (ii) Fission (iii) Tubers (iv) Adventitious Branches (v) Hormogonia (vi) Budding
  12. 12. (i) Fragmentation • The filamentous thallus breaks into fragments, and each fragment is capable of forming new thallus. • The common examples are Ulothrix, Spirogyra, Oedogoniwn, Zygnema, Oscillatoria etc.
  13. 13. (ii) Fission •Fission is common in desmids, diatoms and other unicellular algae. •The cell divides mitotically into two cells are separated by septum formation.
  14. 14. (iii) Tubers • Tubers are spherical or globular bodies formed on lower nodes and rhizoids in Chara. • They are formed due to storage of food. • On detachment of Parent Plant these develop into new plant.
  15. 15. (iv) Adventitious Branches • In some cases, certain adventitious branches are produced which break off from the parent body and develop into new plants. • Common examples are Chara and Dictyota.
  16. 16. (v) Hormogonia • In blue green algae like Nostoc, Cylindrospermum, the main filament breaks into small fragments of varying length called hormogonia. • The hormogonia may be formed at the place of heterocyst in the filaments.
  17. 17. (vi) Budding In Protosiphon budding takes place due to proliferation of vesicles. The buds detach to make new thalli.
  18. 18. (B) Asexual Reproduction (i) Zoospores: (ii) Aplanospores: (iii) Akinetes (iv) Hypnospores: (v) Tetra spores: (vi) Auto spores:
  19. 19. (i) Zoospores: • The zoospores are flagellated formed in reproductive body zoosporangium. • Biflagellate e.g., Chlamydomonas • Biflagellate and quadriflagellate e.g., Ulothrix, Cladophora. • Multi-flagellate e.g., Oedogoniwn. • Move in water before they germinate to make new plants. • Normally formed under favourable conditions. • In Vaucheria, a compound zoospore called synzoospore is formed.
  20. 20. (ii) Aplanospores • Aplanospores are formed under unfavourable conditions. • They are non-motile structures, in which protoplasm gets surrounded by thin cell wall. • The aplanospores on release form new plants, e.g., Ulothrix.
  21. 21. (iii) Akinetes • The akinetes are formed under unfavourable conditions as method of perennation. The akinetes are thick walled, non- motile structures like aplanospores. • Akinetes, on release, form new thalli. e.g., Anabaena.
  22. 22. (iv) Hypnospores • Hypnospores are thick walled structures, formed during unfavorable conditions. • Under prolonged unfavorable conditions, the protoplasm of hypnospores divides to make cysts. • The cysts are capable of forming new thallus. • e.g., Chlamydomonas nivalis.
  23. 23. (v) Tetra spores: •Tetra spores are non-motile spores formed in some members of Rhodophyceae and Phaeophyceae. •In Polysiphonia, tetra spores are formed in tetra sporangia by reduction division on special tetrasporophytic plants.
  24. 24. (vi) Auto spores • The auto spores are aplanospores like structures. These are similar to the parent cell. • In Chlorella, Scenedesmus, auto spores acquire all characteristics of parent cells before their discharge from sporangium.
  25. 25. (C ) Sexual Reproduction (i) Isogamy (ii) Anisogamy (iii) Oogamy a. Hologamy b. Autogamy
  26. 26. (i) Isogamy In isogamous reproduction the fusing gametes are morphologically similar. These gametes are physiologically different due to different hormones. e.g., Chlamydomonas, Ulothrix, Spirogyra and Zygnema.
  27. 27. (ii) Anisogamy • In anisogamy the fusing gametes are morphologically as well as physiologically different. These are formed in different gametangia. • The microgametes/male gametes are smaller, active and formed in large number. • The macrogametes/female gametes are larger, less active and formed in relatively smaller number e.g., Chlamydomonas.
  28. 28. (iii) Oogamy • It is the most advanced type of sexual reproduction. • The male gametes or microgametes are formed in antheridia. • The female gamete is large, usually one and formed in female structure Oogonium. • During fertilization the male gametes reach Oogonium to fertilize egg and a diploid zygote is formed, • e.g., Chlamydomonas.
  29. 29. Hologamy the unicellular thallus of opposite strains (-) and (+) behaves as gametes directly. The thalli fuse to make diploid zygote. e.g., Chlamydomonas. Autogamy two gametes of same mother cell fuse to form diploid zygote. Since both gametes are formed by same cell there is no genetic recombination. e.g., diatoms.
  30. 30. Classification of Algae • Fritsch (1935, 1945) in his book “The Structure and Reproduction of the Algae” proposed a system of classification of algae. • He treated algae giving rank of division and divided it into 11 classes. • His classification of algae is mainly based upon characters of pigments, flagella and reserve food material.
  31. 31. Class 1. Chlorophyceae (= Isokontae) Class 2. Xanthophyceae (= Heterokontae) Class 3. Chrysophyceae Class 4. Bacillariophyceae (diatoms) Class 5. Cryptophyceae Class 6. Dinophyceae Class 7. Chloromonadineae Class 8. Eugleninae Class 9. Phaeophyceae Class 10. Rhodophyceae Class 11. Myxophyceae (= Cyanophyceae) Classification of Algae
  32. 32. Class 1. Chlorophyceae (= Isokontae) • fresh water and chlorophyllous thallophytes. Chlorophyll b & carotenoides are present in chloroplasts. • Cell wall is made up of cellulose. • food is synthesized in the form of starch. • Motile spores and cilia are found. • The sexual reproduction is isogamous, anisogamous and oogamous types. • Chlamydomonas, Volvox, Chlorella, Ulothrix & Spirogyra
  33. 33. Class 2. Xanthophyceae (= Heterokontae) • These are green-yellow in colour due to the presence of xanthophyll. The paranoids are absent • food is in the form of fat. • Chlorophyll e is found in place of chlorophyll b. • The sexual reproduction occurs by fission of two gametes having cilia of different length. • Important genera are: • Microspora, Vaucheria, Protosiphon.
  34. 34. Class 3. Chrysophyceae: • Besides chlorophyll, yellow-green pigments are present. • Phycocyanin is the colouring material. • Plants are unicellular, multicellular or colonial. • The cell wall is present in the form of two overlapping halves. • Stored food is in the form of oil / insoluble carbohydrates, leuosin. • Example: Chrysosphaera.
  35. 35. Class 4. Bacillariophyceae (diatoms) • These are yellow-green-brown or olive green in colour. • Diatomin is the colouring material. • Pyrenoids are also present. • These are unicellular and non- motile. • Chlorophyll c is present in place of chlorophyll b. • Examples: • Pinularia, Navicula, Fragilaria.
  36. 36. Class 5. Cryptophyceae • These are red, green-blue, olive-green or green coloured algae. • Each cell consists of two large chloroplasts in which pyrenoids are present. • They occur in fresh water and sea. • Example: Cryptomonas.
  37. 37. Class 6. Dinophyceae: • These are dark yellow or brown or red coloured algae. • Stored food is oil or starch. • Large nucleus and many discs like chromatophores are present. • Example:Peridinium.
  38. 38. Class 7. Chloromonadineae • These algae are bright green or olive green colour. • Xanthophyll is in abundance. • Fatty compounds acts as food. • Reproduction takes place by longitudinal division. • Example: Vacuolaria.
  39. 39. Class 8. Eugleninae: • They resemble microscopic animal due to presence of naked ciliated reproductive organs. • Chlorophyll is present. • Example: Euglena.
  40. 40. Class 9. Phaeophyceae: • These are yellow-brown coloured marine algae. • Fucoxanthin pigment is the main colouring material. • Storage food materials are laminarian, mannitol . • Zoospores are bi-ciliated and one cilium is larger. • There is no resting period in zygote. • Examples: Fucus, Sargassum.
  41. 41. Class 10. Rhodophyceae • Red in colour due to phycoerythrin pigment. • Storage food is Floridian starch. • Non- motile cells are found during reproduction. • These are commonly found in sea water. • Sexual reproduction is oogamous type. • Chlorophyll d is present in place of chlorophyll b. • Examples: Polysiphonia and Batrachospermum.
  42. 42. Class 11. Myxophyceae (= Cyanophyceae) • The nucleus is of prokaryotic type. • The blue colour is due to the presence of phycocyanin pigment. • The chlorophylls are found in thylakoids. • Storage food is myxophycean starch and protein granules. • There is no motile stage in these algae. • Sexual reproduction is absent. • Mainly these algae are unicellular or filamentous. • Examples:Nostoc, Oscillatoria, Anabaena, Lyngbya, Plectonema.
  43. 43. ECONOMIC IMPORTANCE OF ALGAE • Algae as Food • Algae as fodder for cattle • Utilization of Algae as Fertilizers • Utilization of Algae in water Purification • Utilization of Algae in Medicine & Antibiotic • Use of Algae in Industries • Algae in SewageDisposal • Algae in Land Reclamation • Algae In Biological Research
  44. 44. Conclusion •According to some scientists, algae produce half of the earth’s oxygen. •They are a source of crude oil. These algal biofuels could well be a replacement for the fossil fuels. •Algae also play an effective role in keeping the atmospheric carbon dioxide. •The food industry also uses some algae. Agar is obtained from Gelidium and Gracilaria and is making ice-creams and jellies.The other food supplements that are algae and which are widely used are Chlorella and Spirulina.
  45. 45. REFERENCES •Botany by Y.D. Tyagi •Textbook of Microbiology by R. P. Singh •Textbook of Microbiology by Dubey and Maheshwari •Google Search
  46. 46. THANK YOU