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Chapter, , , , Protista, , , , 1.3, , (Unicellular eukaryotes), , , , , , Characteristics of protista, , Protista (Protistos = Primary) includes unicellular eukaryotes, and show the following characters :, , (1) Profits include solitary unicellular or colonial unicellular, ‘eukaryotic organisms which do not form tissues., , (2) The single cell may be naked or covered by cell wall,, pellicle, cuticle or shell,, , {3) Simple multinucleate organisms or stages of life cycles, ‘occur in a number of groups., , {4) The organisms possess double and porous nuclear, membranes, mitochondria, golgibody, plastids (in many), vacuoles,, lysosomes and ribosomes are also present. Centrosome occur in, , many cases., , (8) In many forms, plastids, (9+2 strand) flagella and other, organelles are present., , {6) Some protists possess contractile vacuole for regulation of, their water content,, , (7) Their reproductive cycles typically include both asexual, divisions of haploid forms and true sexual processes with, karyogamy and meiosis., , (8) The organisms move by flagella or by other means or are, non-motile,, , (9) It may be photosynthetic, holotrophic, saprotrophic,, parasitic and symbionts, Some have mixotrophic nutrition, (holotrophic + saprobic). The photosynthetic, floating protists are, collectively called phytoplankton. The free-floating, holozoic, protozoans are collectively termed zooplankton., , (10) Asexual reproduction is the most common method in, protists. It involve binary fission (Paramecium, Euglena, Amoeba),, multiple fission (Amoeba), plasmotomy (Opalina), budding, (Paracineta, Arcella) and spore formation (Slime moulds)., , (11) Sexual reproduction is believed to have originated in, primitive protists. It involve isogamy (Monocystis), anisogamy (e.g.,, Ceratium) and oogamy (e.g., Plasmodium)., , cl, broadly di, , (i) Photosynthetic protists : e.g, Dinoflagellates, Diatoms,, Euglenoids., , (il) Consumer protists : e.g., Slime moulds or Myxomycetes., Protozoan protists : eg. Zooflagellata, Sarcodina,, , , , sification of protista : Unicellular protists have been, led into three major groups :, , , , , , , , , , ‘Sporozoa, Ciliata, Photosynthetic protists, | Dinofiageliates, General characters, , (1) This is well defined group of unicellular, golden-brown, photosynthetic organisms. Majority of them are motile and, flagellated but a few are non-motile and non-flagellated, Flagellated forms exhibit peculiar spinning movement, Hence, they, are called whorling whips., , (2) The cell wall of dinoflagellates, if present, is composed of a, number of plates made up of cellulose. It is called theea or lorica., The theca contains two grooves-longitudinal suleus and, transverse girdle or annulus., , (3) Usually the cells possess two flagella which are of, different types (heterokont)

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(4) Trichocysts are rod like or spindle shaped ejective, structures which occur just below the cell membrane., , (5) Cells possess a relatively large and prominent nucleus, known as mesokaryon. DNA is without association with histone., , , , (6) There are numerous discoid chloroplasts without, Pyrenoids. They are yellow-brown to dark-brown in colour due to, Presence of characteristic pigments - Chlorophyll a, c, acarotene and xanthophylls (including dinoxanthin and peridinin)., , (7) The cells possess an osmoregulatory organelle called, pusule which superficially looks like contractile vacuole., , (8) In dinoflagellates it is mainly holophytic or photosynthetic., However, some forms are saprobic, parasitic, symbiotic or holozoic., For example, a colourless Blastodinium is parasite on animals., , (9) Dinoflagellates reproduce asexually through cell division or, bby the formation of zoospores and cysts. The cell division starts from, posterior end. During cell division, centromeres and spindle are not, seen., , (10) If sexual reproduction occurs, is isogamous or, anisogamous. Two cells conjugate by a conjugation canal where, the two amoeboid gametes fuse to form a diploid zygote. Life cycle, involves zygotic meiosis (eg, Ceratium, Gymnodinium etc.) or, gametic meiosis (e.g., Noctiluca)., , , , Examples : Glenodinium, Peridinium, Gymnodinium,, Gonyaulax, Ceratium, Noctiluca,, Epivalve ‘Transverse, flagellum, Hypovalve, Longitudinal, flagellum, , , , (a), , Fig: 1.3-1 Some dinoflagellates (a) Glenodinium, (b) Peridinium (c) Gynnodium (d) Gonyaulax, , , , General character, , (1) Most of the diatoms occur as phytoplanktons both in, fresh and marine waters. A few forms occur as benthos the bottom, of water reservoirs, Diatoms constitute a major part of, phytoplankton of the oceans,, , (2) The cells of diatoms are called frustules or shell. They are, microscopic, unicellular, photosynthetic organisms of various, , , , , , : a, , colours and diverse forms, They may be circular, rectangular,, triangular, elongated, spindle-shaped, halmoon shaped, boatshaped or filamentous. Incipient filament occur in Mefosira., , (3) They exhibit mainly two types of symmetry-radial, symmetry as in centrales (eg, Cyclotella, Biddulphia,, Triceratium, Mefosira) and isobilateral symmetry as in Pennales, (eg., Pinnularia, Synedra, Actinella, Nevicula)., , (4) The cell wall is chiefly composed of cellulose impregnated, With glass-like silica. It shows sculpturings and ornamentations. It is, composed of two overlapping halves (or theca) that fit together ike, two parts of a soap box. The upper half (lid) is called epitheca, and the lower half (case) is called hypotheca,, , (6) Diatoms do not possess flagella except in the reproductive, stage. They show gliding type of movement with the help of, mucilage secretion. They float freely on the water surface due to, presence of light weight lipids,, , (6) Each cell has a large central vacuole in which a prominent, nucleus is suspended by means of cytoplasmic strands. The cells, are diploid (2N). In case of centrales, the nucleus lies in the, peripheral region., , (7) Some species of diatoms are devoid of chromatophores,, e.g, Nitzschia alba, They are saprotrophic in nutrition,, , (8) The reserve food material is oil and a polysaccharide —, chrysolaminarin (or leucosin)., , (9) Most common method of multiplication is binary fission, {cell division) that occurs at night., , (10) Sexual reproduction takes place by the fusion of gametes., Meiosis is gametic te, takes place during the formation of, gametes., , Examples : Triceratium, Pleurosigma, Navicula, Cymbella,, Amphipleura, Niteschia, Melosira, Pinnularia., , I glenoid, , General characters, , (1) Euglenoids and their non-motile relatives are unicellular, flagellate protists,, , (2) These protists are devoid of cellulose cell wall. The body is, covered by thin and flexible pellicle. The pellicle has oblique but, parallel stripes called myonemes. The pellicle is composed of, fibrous elastic protein and small amount of lipid or carbohydrates,, , (3) The euglenoids have two flagella, usually one long and, , one short. Each flagellum arises from a basal granule, (blepharoplast), The flagella bear hair,, , (4) They can undergo creeping through expansion and, contraction of body called metaboly.

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cytostome (mouth), cytopharynx (gullet or canal) and reservoir., The cytostome is generally eccentric., , (6) The two flagella join with each other at a swelling called, paraflagellar body. An orange red coloured eye-spot or stigma is, located at the base of flagellum attached to the membrane of, reservoir at the level of paraflagellar body. They contain red, pigment astaxanthin. Both paraflagellar body and eve spot act as, , photoreceptors and direct the organism towards the optimum light., (7) An osmoregulatory contractile vacuole occurs in the, , anterior part of the cell below the reservoir., , , , (8) Nutrition is holophytic (photoautotrophic), saprobic (e.g,, Rhabdomonas) or holozoic (e.g, Peranema). Even holophytic, forms can pick up organic compounds from the outside medium., Such a mode of nutrition is called mixotrophic., , (9) Product of photosynthesis is paramylon which is stored in, the form of paramylum granules in the paramylum bodies in, cytoplasm,, , (10) Sexual reproduction has not yet been definitely proved., ‘Under favourable conditions, euglenoids multiply by longitudinal, binary fission., , (11) These protists perennate during unfavourable periods, as cysts., , Example : Euglena, Phacus, Eutreptia, Trachelomonas,, , Peranema. =, , General characters, , (1) Euglena is a connecting link between animals and plants., , (2) Euglena resembles the ancestral form from which the, plants and animals evolved., , (3) Euglena is a free swimming fresh water flagellate which, moves by two different methods :, , (i) Euglenoid movement (wriggling movement), by contraction, and expansion of the body., , (ji) Flagellar movement, with the help of sticonematic type, flagellum,, , (4) Body is covered by pellicle, a small cytostome (cell mouth), and cytopharynx is present at the anterior end of the body., , (5) Euglena contains chlorophyll, yet it resembles animals,, because it feeds like animals in the absence of sunlight., , (6) Nutrition in Euglena is mixotrophic, when light is available, ft is photosynthetic, in darkness it is saprophytic absorbing food, from surrounding water., , (7) Reserve food is stored in the form of paramylum or, paramylon,, , (8) Asexual reproduction occurs by longitudinal binary fission,, no sexual reproduction., , Fig: 1.3-2 Euglena viridis, , Consumer / Decomposer protists, , {Stim moulds, , Slime moulds include very interesting and peculiar organisms, which share the characters of both animals and fungi. Due to this, peculiarity they are commonly called fungus animals. Modem, biologist include slime moulds under the kingdom-protista and, called them protistan fungi., , General characters, , (2) They do not have chlorophyll., , (2) They are surrounded by the plasma membrane only, (somatic parts are without cell walls), (3) At one stage of the life cycle they have amoeboid structure,, (4) The slime moulds live usually amongst decaying, vegetation. They are quite common on lawns and moist fields., , (5) They have phagotrophic or saprotrophic nutrition., Parasitic forms are not known, , (6) The sporangia produce spores. Each spore possesses a, cellulose cell wall., , Acellular (Plasmodial) Slime moulds, General characters, , (1) Acellular slime moulds commonly grow as slimy masses on, damp places rich in dead and decaying organic matter., , (2) The somatic phase is diploid and consists of a free living, organic matter multinucleated protoplasm called plasmodium.

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Protista (Unicellular eukaryotes) 57, , , , , , (3) The plasmodium slowly streams or glides over decaying, organic matter putting out blunt finger like pseudopodia showing, amoeboid movement., , (4) They also absorb dissolved organic substances from the, ‘substratum showing saprotrophic nutrition., , (5) Each plasmodium reproduces asexually by the formation, of several, smal, sessile or stalked, brightly coloured sporangia., , (6) When fully mature, the wall of the sporangium bursts to, release the spores. The spores are dispersed by air., , (7) On germination, a spore generally releases one biflagellate,, spindle-shaped swarm cell or a non-flagellate myxamoeba. The, myxamoebae feed on bacteria and yeasts and multiply in number., The swarm cells swim about actively and finally fuse in pairs at the, Posterior nonflagellate ends to form zygotes., , (8) The diploid nucleus of zygote undergoes repeated mitotic, divisions. As a result, the zygote gradually changes into a, multinucleate amoeboid structure, the plasmodium. The, plasmodium repeats the life cycle,, , Examples : Physarum,, Lucogala, Tubifera., , Sporangium, , Physorella, , Fullgo,, , Dictydium,, , , , , Spore, Germinafing, , , , , =) Zygote, Young plasmodium ss >, Fig: 1.3-3 Diagramatic life cycle of, acellular Slime mould (e.g., Physarum), , Cellular Slime moulds, , General characters, , (1) The cellular slime moulds occurs in the form of haploid, uninucleated, naked (without cell wall) cell covered by plasma, membrane. These cells are called myxamoebae., , (2) The myxamoebae move freely with the help of amoeboid, movement and phagotrophic or holozoic nutrition,, , (3) Under unfavourable condition a myxamoeba secrete a, tigid cellulose wall to form the microcyst. Microcyst formation is a, means of perennation., , The microcysts can be dispersed. On the return of favourable, conditions, the microcyst wall ruptures to release a myxamoeba., The latter resumes its function of feeding, growth and, multiplication forming amoeboid cells., , (4) When the food supply is exhausted the amoeboid cells get, aggregated without any fusion. The stimulus for the aggergation, Process is due to release of cyclic 3',5' adenosine monophosphate, (cyclic AMP) from the amoeboid cells. This aggregated mass of, cells is called pseudoplasmodium, It is a sort of community, association. Because of this reason, cellular slime moulds are called, the communal slime moulds,, , (5) The stalk of sporocarp may remain upright or bend. Finally, the spores are released and disseminated,, , (6) The most important character of cellular slime moulds is, the complete absence of flagellated cells in their life cycle., , (7) The cellular slime moulds resemble plant in having, cellulose cell wall in spores and resemble animals in having, amoeba-like myxamoebae., , Examples : Dictyostelium, Polysphondylium,, , Z Z, == —_, , ae —, , a, a, , j:, /, 4, , es, a ) &, oe Stall L, orinting “|, , Spore, , ‘Substratum, , Paeuo sna, , , , Ambeboid cells, , ‘Myxamoeba, porangiam,, , Fig : 1.3-4 Diagramatic life cycle of cellular slime mould, Protozoan protists (Gr. Protos = first ; zoon = ani, , , , It include all unicellular (or acellular) eukaryotic animals., These are most primitive organisms considered as animals because, of heterotrophic nutrition and motility. About 50,000 species, {30,000 present and 20,000 extinct) are so far known., , Brief history : Protozoans were first studied by, Leeuwenhoek (1677). The name “Protozoa” was coined by, Goldfuss (1817). The branch of their study is called Protozoology., , General characters, , (1) Protozoans are the simple and primitive organisms., , (2) They are free living or parasitic,

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(3) They are asymmetrical or radially symmetrical or bilaterally, symmetrical., , (4) They are unicellular (acellular)., , (5) They have protoplasmic grade of organization., , (6) Locomotion is effected by flagella, cilia or pseudopodia., (7) Nutrition is holophytic, holozoic, saprozoic or parasitic., (8) Digestion is intracellular., , (9) Excretion and respiration occurs by diffusion., , (10) In fresh water protazoans osmoregulation is carried out, by the contractile vacuoles., , (11) Reproduction occurs by asexual and sexual methods., , Classification of Protozoans, , Protozoans are classified on the basis of locomotory organelles, into following classes., , Class 1. Rhizopoda or Sarcodina, , (1) There is no definite cell wall or pellicle., , (2) There is no definite shape., , (3) The locomotory organs are pseudopodia,, , (4) There is no permanent mouth or anus,, , (6) The contractile vacuoles are present in the fresh water forms., , ‘The thizopoda has been divided into five orders. They are as, Lobosa, Filosa, Foraminifera, Heliozoa and Radiolaria., , Examples : Amoeba, Entamoeba histolytica, Entamoeba coll,, Pelomyxa, Globigerina, Actinophryx., , 1 InArcelia has an exoskeleton of tactin., , OQ. Giardia is called ‘Grand old man of intestine’,, , Q_Adtinophryx is called ‘Sun animalcule' as it resemble the sun., , Class 2. Flagellata or Mastigophora, , (1) The body is covered by a thin pellicle or cuticle., , (2) The locomotory organs are flagella, , (3) The contractile vacuoles are present in fresh water forms, with accessory vacuoles., , (4) Chloroplast are found in some forms., , (5) They may be free living or parasitic., , The class flagellata has been divided into eight orders. They, areas Chrysomonadina, Cryptomonadina, Euglenoidea,, Phytomonadina, Dinoflagellata, Cystoflagellata, Protomonadina, and Polymastigina., , Examples Chrysamoeba, Cryptomonas,, Chlamydomonas, Noctiluca, Mastigamoeba, Monal,, Trypanosoma, Leishmania, Proterospongia etc., , Voluox,, Bado,, , Q Trychonymph (symbiotic) live in alimentary canal of, termite that is digest to cellulose., , Q. Noctiluca shows bioluminiscense due to luciferin protein., Itis also called the ‘Fire of sea’., , Class 3. Sporozoa, , (1) They are exclusively endoparasitic., , (2) The body is covered by pellicle., , (3) Reproduction takes place by spore formation,, , “The class is divided into two sub-classes, namely, Telosporidia, and Neosporidia., , Sub-class (i) Telosporidia, , (1) The spores do not contain polar capsules or filaments., , (2) The life history ends with the formation of spores., , (3) The spore cases are simple and contain many spores., , Examples : Monocystis, Gregarina, Isopora, Eimeria,, Plasmodium, Babesia etc., , Babesia causes the ‘Taxas cattle fever’ in animals. This, disease also called ‘Red water fever’ or Haemoglobin uric fever., , QQ Monocystis is found in seminal vesicle of earthworm, and, causes sterlity in earthworm. It is monogenetic in nature., , (Eimeria is found in epithelial cells of liver of Rabbit., ‘Sub class (ii) Neosporidia, , (1) The trophozoite is amoeboid multinucleated., , (2) Spore cases are complex usually having a single germ., Examples : Nosema, Myxidium, Globidium etc., , Class 4. Ciliophora, , (1) Th. body is covered by thin pellicle., , (2) They have a fixed permanent shape., , , , (3) The locomotory organs are cilia., (4) Tentacles are present., , (5) Nuclei are usually of two kinds micronucleus and, meganucleus., , ‘The class ciliophora is divided into two sub-classes, namely, Ciliata and Suctoria., , Sub-class (i) Ciliata, (1) Cilia are present throughout life., (2) Tentacles are absent., , (3) Mouth and eyiopharynx are usually present, Cytopyge is a, temporary anal apperture., , (4) Contractile vacuoles are present,, , (5) Trichocysts, organs of offense and defence are present in, certain forms., , Examples : Paramecium, Stylonchia Vorticelia etc., , O Vorticella is called ‘Bell animalcule’. It is a pedicellate, protozoan,, , 1 Nyctotherus is a parasite in the rectum of frog. It is also, found in the rectum of cockroach,, , Sub-class (ii) Suctoria, , (1) Cilia are present only in the young conditions and adults, are devoid of them., , (2) Tentacles are present in the adult., , (3) One to many contractile vaculoes are present., , Examples : Acineta, Ephelota, Dendrocomeies, Dendrosoma etc.