Biological Classification


  • Many protist live in aquatic as planktons and some live as parasites.
  • Three major groups of Protista are (i) Photosynthetic protist (ii) Consumer - Decomposer and (iii) Protozoan Protista.
  • Dinoflagellates, chrysophytes and Euglenoids are the 3 classifications of photosynthetic Protista.
  • Dinoflagellates like Gymnodinium and Gony acylase causes red tide and bioluminescence. Eg. Noctiluca (The Night Light).
  • Cells are covered with theca with cellulose sculptured and hence called armoured dinoflagellates.
  • Their plastid contains chlorophyll ‘a’ and ‘c’.
  • Reserve food is stored in the form of oil and starch.
  • The toxins of dinoflagellates accumulate in shell fish, which when consumed by man leads to paralytic shell poisonings (PSP) which may be fatal.
  • Chrysophytes include Diatoms and Desmids, which belong to the division chrysophyta / Bacillariophyta.
  • Diatoms form Diatomaceous earth / Diatomite at the bottom of water reservoirs, which has a body called Frustule, made up of 2 values called epitheca and hypotheca.
  • Diatoms contain chlorophyll ‘a’ and ‘c’ with fucoxanthin.
  • Reserve food material is oil, Leucosin and Volutin granules.
  • Euglenoids possess pellicle instead of the cell wall and they are unicellular flagellates.
  • Nutrition is mixotrophic (holozoic + holophytic)
  • Flagellum bears paraflagellar bodies which contain an orange – red-eyed spot (stigma) with a pigment astaxanthin, used to perceive the stimulus of light.
  • Euglenoids have chlorophyll ‘a’ and ‘b’.
  • Reserve food material is Paramylum bodies [different from starch and glucogen]
  • Reproduction is by longitudinal binary fission. [Eg: Euglena, Phacus, Peranema etc.,]
  • Consumer – Decomposer Protista includes slime moulds, commonly called as Fungus – animals, which are of 2 types – (i) Acellular and (ii) Cellular (has plant characteristics).
  • The acellular form is called Plasmodial moulds, which are found in dead and decaying leaves. Eg. Physarum, Physarella, Tubifera, Fuligo and Lycogala.
  • Their somatic phase is diploid multinucleated plasmodium.
  • They lack chlorophyll and are colourless.
  • The life cycle of a cellular form starts by forming sporangia (fruiting bodies) → spores → Germination → Sexual reproduction → Formation of Plasmodium.
  • Cellular slime moulds (Acrasiomycetes) occur in humus, where their somatic phase is haploid and so they are uninucleate cells (Myxamoebal cells).
  • When food supply is completed, amoeboid cells aggregate due to their release of C-AMP (cyclic AMP) and form Pseudoplasmodium. Eg: Dictyostelium, Polysphondilium.
  • Protozoans are into 4 groups
    (i) Flagellated protozoans
    (ii) Amoeboid protozoans
    (iii) Sporozoans
    (iv) Ciliated protozoans
  • Flagellated type is covered by a pellicle Eg: Giardia, Trypanosoma, Leishmania.
  • Trypanosoma Gambiense causes Africol sleeping sickness through tse – tse fly.
  • Amoeboid protozoans develop Pseudopodia as temporary protoplasmic out-growths.
  • Nutrition is holozoic and they are covered with plasma lemma
    Eg: Amoeba proteus, Pelomyxa, Entamoeba histolytica
  • All sporozoans are Endo parasites where no locomotory organs are present.
  • Asexual reproduction happens through multiple fission and syngamy represents sexual reproduction.
  • The life cycle may be mono (or) digenetic. [Eg. Plasmodium, Monocystis, Eimeria]
  • Eimeria causes coccidiosis in adult birds.
  • Female Anopheles mosquito is the definitive/primary host of Plasmodium as sexual reproduction happen and human is considered as Intermediate/secondary host as Asexual reproduction occur and so they are digenetic
  • Infective stage of Plasmodium is sporozoite.
  • P. vivax, P. falciparum, P. ovale and P. Malariae are its 4 types.
  • Ciliates show Nuclear dimorphism, i.e., they possess micronucleus and meganucleus. Micronucleus helps in reproduction and meganucleus controls metabolic activities and hence called the Vegetative nucleus.
  • Ciliates also contain trichocyst for defence.
  • Asexual reproduction occurs through transverse binary fission (or) budding and sexual reproduction is by means of conjugation, Eg. Paramecium, Vorticella, Opalina, Balantidium etc.,
  • Paramecium (or) slipper animalcule is a surface feeder and its cilia at the posterior end are longer and hence called caudal tuft.
  • Paramecium has 2 contractile Vacuoles, surrounded by 6-12 feeding canals.
  • Food vacuoles are also present for intracellular digestion.
  • Mega nucleus shows Hemiris, where macronucleus breaks first into few irregular pieces and later reunite to form macronucleus. Thus it is also called Purification set.
  • Killer and sensitive paramecium are its 2 types which possess and don’t possess kappa particles respectively. Kappa particles are poisonous agents.

View this video for the topic from 0:10 to 9:17

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