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Classification of Algae

Algae Classification and Life Cycle

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Classification of Algae

  1. 1. Classification Of Algae & Life Cycle of Algae Presented by U.Sharmila
  2. 2. Algae “The algae are chlorophyll bearing organisms which possess unicellular sex organs or multicellular ones in which every cell forms a gamete”
  3. 3. Introduction • They are aquatic both marine and freshwater and occur on and within soil and on moist stones and wood as well as in association with fungi and certain animals. • It is thought that 90 percent of the photosynthesis on earth is carried on by aquatic plants. • Certain blue-green algae, like some bacteria can use gaseous nitrogen from the atmosphere in building their protoplasm and in this way they increase the nitrogenous compunds in water and soils of their habitat. • This activity is called nitrogen fixation
  4. 4. Introduction cont. • These are approximately 1800 genera with 21,000 species which are highly diverse with respect to habitat , size, organization , Physiology ,biochemistry and reproduction. • Phycology is the study of algae
  5. 5. History of Algae • The algae as such have a history that is as old as that of other plants .The first references to algae are to be found in early Chinese literature but there are also references in Roman and Greek literature • Upto about 1800AD. Almost all algae were placed in one of four great genera • Ie., Fucus, Ulva, Conferva and Corallina.
  6. 6. History of Algae Cont. In the 17th Century the Utilization of brown seaweeds for fertilizers was known in France. In those days Agar making art was newly discovered in China and Japan.
  7. 7. Classification of Algae • For the first time Aristole (382-322 B.C) and his pupil Theophrastus (372-287 B.C). • The Father Of Botany Classified the plants into three groups ie. Trees, Shrubs and Herbs. • Linnaeus divided his order Cryptogamia into four suborders. Filices(Pteridophytes) Musci (mosses and leafy liverworts) Algae(algae,lichens and thallose liverworts) Fungi • The First natural System of Classification of the Plants into 3 groups ie.Acotyledons Monocotyledones Dicotyledones
  8. 8. Classification of Algae conc. • In 1880,the Cryptogamic plants were divided into three major groups. Thallophyta(algae,fungi and Bacteria) Bryophyta Pteridophyta • Before Twentieth century only four classes were recognized among alage ie. 1) Chlorophyceae 2) Phaeophyceae(included Diatoms) 3) Rhodophyceae 4) Myxophyceae or Cyanophyceae • Rabenhorst in 1863,for the first time placed the Chlamydomonas,Volvox series in the Chlorophyceae of Algae.
  9. 9. Classification of Algae conc. • According to Dr.F.E.Fritsch (1935,1944,1945) the algae have been divided into following eleven classes 1)Chlorophyceae 7)Chloromonadineae 2)Xanthophyceae 8)Euglenophyceae or 3)Chrysophyceae Euiglinieae 4)Bacillariophyceae 9)Phaeophyceae 5)Cryptophyceae 10)Rhodophyceae 6)Dinophyceae 11)Myxophyceae
  10. 10. According to Dr.Fritsh’s Classification is mainly based on the following facts:- • Pigmentation • The assimilatory food products • Type of Flagella We will consider the characters of few important classes  Chlorophyceae  Xanthophyceae  Bacillariophyceae  Phaeophyceae  Rhodophyceae  Myxophyceae
  11. 11. Life Cycle Patterns In Algae Many Life Cycle patterns are found in algae. However, there is no regular and fixed alternation of generation, as found in higher plants. In blue-green alage and certain Chlorophyceae which reproduce asexually,there is no alternation of generation. The representative life –cycle Patterns in algae are as follows. • Haplontic type • Diplontic type • Isomorphic type • Heteromorphic type • Haplobiontic type • Diplobiontic type
  12. 12. Haplontic Type Haplontic Type: This is the Simplest and Most Primitive type of life-cycle. The other patterns of life cycle have originated from this type. This type is found in all Chlorophyceae except a few. Sometimes this is called Ulothrix or Chlamydomonad type.
  13. 13. Diplontic type Diplontic type. This pattern is reverse of haplontic type.In this case somatic phase is diploid while the haploid phase is restricted to gametes which are produced by meiotic division eg Fucus , Sargassum
  14. 14. Isomorphic type Isomorphic type In this type there are two exactly similar somatic phases showing alternation of generation. Here the one phase is diploid while the other haploid Among chlorophyceae this is found in Ulvaceae
  15. 15. Heteromorphic type Heteromorphic type This pattern of life cycle is exactly like that of preceding one only with the difference that the alternating haploid (n) and diploid (2n) somatic phases are morphologically different. The diploid multicellular sporophytic plant produces haploid zoospores by meiosis.These zoospores develop into gametophytes.
  16. 16. Haplobionatic type Haplobionatic type In this pattern there are three phases in the life cycle.out of three,two phases are haploid (n) and one diploid (2n).The examples are found among Rhodophyceae
  17. 17. Diplobiontic type Diplobiontic type This type of life cycle is found in almost all Rhodophyceae except Nemalionales.The most common example is Polysiphonia. There are several patterns of life cycle in alage and there is no regular and fixed alternation of generations as found in higher plants
  18. 18. Reference College Botany Vol I;B.P.Pandey;published by S.Chand & Company Pvt.Ltd.;5th edition. Net Sources.