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Algae

This slide helps to know about the general characteristics, habit and habitats, range of thallus structure of algae

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Algae

  1. 1. ALGAE
  2. 2. What is algae? • Algae are chlorophyll bearing thallophytes in which the sex organs are wither unicellular or multicellular and not presented by sterile envolope • Algae – derived – latin word – alga : washed away plants on sea shore or sea weeds • Can able to produce many celled sex organs • No sterile cell in sex organ except chara.
  3. 3. • The study of algae is called algology or phycology. • Phycology – Greek word phycos – meaning sea weeds • First introduced by Linnaeus in 1754 • Algae – Greek word – Phykos • Chinese – Tsau • Hawaii – Limu • Roman – Fucus • Tamil - Pasigal
  4. 4. Salient features of algae • Live in moist and aquatic habitats • Unicellular or multicellular • Plant body is thalloid • Presence of chlorophyll and other photosynthetic pigments in chromatophores • Autotrophic in nutrition • Cells may be uninucleate or multinucleate • Cell wall rich in cellulose • Cells motile due to the presence of flagella or cilia
  5. 5. • Reserve food – starch • Reproduction – • Primitive algae – vegetative methods • Higher forms – sexual and asexual reproduction • Asexual reproduction – motile zoospores • In unicellular – entire organisms act as a gametes • In multicellular – gametes produced from unicellular and multicellular gametangium [no sterile jacket]
  6. 6. • Sexual reproduction – isogamous, anisogamous and oogamous • Zygote develops a thick wall to form an oospore • Life cycle – isomorphic or heteromorphic • Life cycle – haplontic, diplontic, diplohaplontic, haplobiontic and diplobiontic • Alternation of generations is common in algae
  7. 7. Habits and Habitats of algae • On the basis of habitats in which algae are growing, there are seven groups – »Aquatic algae »Edaphic algae »Aerial algae »Cryophytic algae »Symbiotic or endophytic algae »Endozoic algae »Parasitic algae
  8. 8. Aquatic algae • Also called as hydrophilous algae • Submerged or free – floating • Living in fresh waters – ponds, rivers, springs etc. • Some in salt water – seas and oceans • Still waters – ponds, pools etc Eg: Zygnema, Oedogonium etc. • Running water – Eg: Vaucheria and Cladophora
  9. 9. Types of aquatic algae i. Benthic algae • Algae which are found attached to any substratum in the bottom of water bodies • It is also called as benthophytes • Eg. Chara, Nitella, Cladophora etc.
  10. 10. ii. Epactic algae • Algae which are found attached to the substrata along the shores • It is also called as epactiphytes • Eg. Oedogonium, Spirogyra etc. iii. Thermophilic algae • Algae which lives in hot springs at around 55⁰C and above • It is also called thermophilic algae or thermophytes • Eg. Oscillatoria sps.
  11. 11. iii. Phytoplankton • Algae that float on surface of water • It is also called planktophytes • Attached during early stages and then become free floating – Tychoplanktophytes • Eg. Oedogonium, Cladophora, Sargassum and Nostoc • Some others remain free floating throughout the life – Euplanktophytes • Eg. Chlamydomonas, volvox etc.
  12. 12. Epizoic algae • Algae that live on aquatic animals are called epizoic algae • It is otherwise called epizoophytes • Eg. Filaments of Cladophora are found attached to the snail shells
  13. 13. Epiphytic algae • Algae that live on other aquatic plants are called epiphytic algae or epiphytes • Eg. Oedogonium, Chara, Nitella etc. Halophytic algae • Algae which are living in salt water such as seas, oceans • It is called as halophytes • Eg. Chlamydomonas etc.
  14. 14. Edaphic algae • Algae which are living in or on the moist soils • It is also called edaphophytes or terrestrial algae • Some sps. live in the suface of soil where organic matter is abundant – saprophytes epiterranean. Eg. Vaucheria • Algae which live bolow the soil surface – cryptophytes [subterranean]. Eg. Anabaena, Nostoc etc.
  15. 15. Aerial algae • Algae living in terrestrial plants, animals, walls, fencing wires, and rocks. • Epiphyllophytes – live in leaves. Eg. Phyllosiphon • Epiphloeophytes – live in bark. Eg. Trentipohlia • Epizoophytes – live in terrestrial animals. Eg. Chaetophora • Lithophytes – live in rocky substratum. Eg. Scytonema
  16. 16. Cryophytic algae • Algae that live in ice or snow – field • It is also called cryophytes • Ice fields – Ancyclostoma • Ice – temporarily – Gleocapsa and Phormidium • Ice and snow – Cylindrocystis and Trochiscia • Alpine Snow fields – red colour – Haematococcus • Green colour – Raphidonema • Red snow – Scotiella • Yellow or Yellow green snow – Ulothrix and Nostoc
  17. 17. Ancyclostoma TrochisciaPhormidium Cylindrocystis Raphidonema Haematococcus Scotiella Ulothrix Nostoc
  18. 18. Symbiotic or endophytic algae • Algae that live in symbiotic association with other plants • It is called as symbionts or endophytes Eg. Lichen. • Some algae seems to be lichen Eg. Chrococcus, Microsystis, Chlorella, Cytonema etc. • Anabaena azollae – leaf tissue of aquatic fern Azolla [Gymnosperm] • A. cycade – corrolloid roots of Cycas [Gymnosperm] • Nostoc – cavities in the thallus of anthoceros [Bryophytes] • Chlorochytrium – inside Lemna [Angiosperm]
  19. 19. Endozoic algae • Algae that live in the aquatic animals • It is called endozoic algae or endozoophytes • Zooxanthellae is found in fresh water sponges • Zoochlorella – inside the body of Hydra • Characium – seen in some body of insect larvae
  20. 20. Parasitic algae • Algae that live as parasite on other plants are called parasitic algae • Causes diseases in some plantation crops • Eg. Caphaleuros virescens – parasitic algae of tea and causes red rust disease
  21. 21. Range of thallus structure in Algae
  22. 22. I. Unicellular Algae: It is of two types a. Motile forms or flagellated forms a) Freely moving in water by flagella b) They are of many shapes – spherical, oblong or pear shaped and circular – Ex. Chlamydomonas c) Some are dorsiventrally differentiated – Ex. Phacus d) The number of flagella may to one to more and it may be equal or unequal
  23. 23. • Euglena – one flagellum at its anterior • Chlamydomonas – two flagella at its front end • Heterochlorsis – two flagella and unequal • Botrydiopsis – two flagella i. acronematic or whiplash ii. pantonematic • Peridium – two flagella »arises from transverse furrow and encircles the cell »arises from longitudinal furrow and faces backward • Trichloris – three flagella • Carteria – four flagella • Chloraster – five flagella • Pocillomonas – six flagella
  24. 24. Amoeboid forms or periplasts or naked forms • In some forms there is no true cell wall so that the shape of the cells is flexible. Eg. Heterochloris mutalis Rhizopodial forms • Some motile cells after shedding their flagella long develop delicate cytoplasmic process called rhizopodium. Eg. Synura Encapsulated forms • Some motile unicells are enclosed by thick, variously shaped envolope. Eg. Phacotus Colourless forms • Some saprophytic motile unicells remain colourless
  25. 25. Euglena Euglena Chlamydomonas Heterochlorsis Carteria Synura Phacotus
  26. 26. b. Non flagellated or coccoid forms • The unicellular non – flagellated forms are called coccoid forms • The cells are more or less round and bounded by rigid cell wall Eg. Chlorella and Chlorococcus • The cell may be enclosed by sculptured calcareous scales called coccolith. This form is called cocosphere. Eg. Calcidiscus and diatoms • The cell is elongated and spirally coiled in Spirulina • The cell is spindle shape in Closterium
  27. 27. Chlorella Chlorococcus Spirulina Closterium
  28. 28. II. Multicellular Algae (or) colonial forms: A group of individual cells of a species living in a habitat is called a colony. It is of two types a. Motile colonial forms (or) Coenobial forms • Colony in juvenile and mature stages remains constant – coenobium • It is called as motile coenobium • Motile Eg. Volvox, Gonium, Pandorina etc. • A Volvox colony has many Chlamydomonas cells interconnected by protoplasmic connections • The surface of the colony is covered with mucilage – lamella and the center remains hollow at several regions. It is called hollow type coenobium
  29. 29. • Gonium colony consists of 4 – 32 closely arranged Chlamydomonas type cells surround by mucilaginous cells • Pandorina colony has 16 – 32 cells covered with a common mucilaginous sheath Volvox Pandorina Gonium
  30. 30. b. Non Motile colonial forms • If the individual cells are non – flagellated, the coenobium remains non – motile. Eg. Hydrodictyon, Pediastrum, Senedesmus etc. • The Coenobium of Hydrodictyon consists of many cylindrical cells which are joined end to end like hexagons. • Hence the colony appears to be a network Hydrodictyon
  31. 31. • The colony of Pediastrum is disc shaped and is made of closely arranged cells • In Scenedesmus, the colony consists of 4 – 8 variously shaped cells which are parellely arranged one above the other as a stack of coins Pediastrum Scenedesmus
  32. 32. c. Palmelloid forms or Amorphous forms • An algal colony in which non – motile cells are embedded in an amorphous gelatinous matrix is called palmelloid colony or palmelloid form. • The gelatinous matrix may be secreted by protoplasts of the individual cells of the colony • Eg. Tetraspora, Chlorosaccus and Phaeocystis Tetraspora Chlorosaccus Phaeocystis
  33. 33. Palmella – stage • The division of the protoplast of a cell ultimately forms amorphous colony with indefinite number of spores and it is called palmella stage.
  34. 34. d. Dendroid forms • A colony, in which the individual cells are jointed end to end by producing mucilage at their base end which looks like a branched tree. • It is also called dendroid family • Eg. Prasinocladus, Dendobryon etc. Dendobryon Prasinocladus
  35. 35. e. Rhizopodial form • A colony in which the individual cells are linked together by means of rhizopodia is called rhizopodial forms or rhizopodial colony. Eg. Chlorarachnion Chlorachnion
  36. 36. f. Filamentous forms • An algal thallus in which cells are arranged in linear row and are joined end to end by middle lamella is called a filament or filamentous form Uniseriate filament – The filament is made of single row of cells. Eg. Ulothrix, Oedogonium. [prokaryotic cells] Multiseriate filament – The cells are arranged in more than one linear row. Eg. Ulva
  37. 37. • The filamentous forms may be branched or unbranched Unbranched types - • simple with linear row of cells Ex. Ulothrix • Leaf – like Ex. Ulva • Tubular Ex. Enteromorpha Ulva Enteromorpha
  38. 38. • Filamentous thalli with lateral branches is called branched filaments Types of branched thalli Pseudo branches • In some algae, the filaments breaks at certain points due to the disintegration of cells • The cells adjacent to the dead cells grow out of the mucilagenous sheath called Pseudo branches • The formation of Pseudo branches is called false branching. Eg. Scytonema Scytonema
  39. 39. True branches • The lateral branches arise due to the transverse division of cells in lateral outgrowths. Ex. Cladophora Parenchymatous cells – Eg. Ulva Pseudoparenchymatous cells – Eg. Polysiphonia and Gracilaria Cladophora Polysiphonia Gracilaria
  40. 40. g. Heterotrichous forms • The filaments which contains both prostrate system and erect system is called heterotrichous form • Hetero – different; trichous – filament • The thallus was differentiated into creeping system and projecting system • Creeping system – consists of branched filaments attached to the substratum • Projecting system – arises from the creeping system and grows erect
  41. 41. Eg: • Fritschiella – both creeping and erect equally developed • Coleochaete– creeping system – disc like and well developed. Prostrate system – poorly developed • Drapernoldiopsis– prostrate system – well developed. Creeping system – poorly developed
  42. 42. h. Siphonous forms • Here the thallus is an elongated cell which contains numerous nuclei, chromatophores, pheripheral cytoplasm and a central narrow vacuole. • This type of thallus is called siphon or siphonous form Eg. Vaucheria and Protosiphon
  43. 43. i. Advanced type of Thalli • The thallus consists of a combination of filaments and parenchymatous cells • Thallus may be uniaxial or multiaxial • Uniaxial thallus – main thread surrounded by numerous lateral branches as cortex. Eg. Batrachospermum • Multiaxial thallus – has the main axis has many threads surrounded by their lateral branches. Eg. Polysiphonia
  44. 44. • In Chara, the thallus bears rhizoids to attach it with substratum and the branched erect system • In Sargassum – differentiated into root – like, stem – like and leaf – like structures consists of parenchymatous cells • In Postelsia palmaeformis – thallus is palm – like and its cells are parenchymatous
  45. 45. Evolution of Thallus in Algae • Acco’ to evolutionary theories, the motile unicells are the simple and primitive type of thalli • The coccoid forms developed from the flagellated forms by shedding their flagella • The colonial forms developed by the aggregation of motile or non – motile forms • The filamentous forms evolved from unicells by the joining of many cells end to end
  46. 46. • The leaf – like filamentous thalli evolved from the uniseriate simple filaments by lateral and transverse divisions of their constituent cells. • Heterotrichous filaments have evolved from simple filamentous forms due to the repeated cell division and aggregation of resulting filaments. • Heterotrichous forms are considered to be the ancestors of advanced type of thalli
  47. 47. THANK YOU

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