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Protozoa Over all View By –V.PARTHASARATHY –Lecturer in Zoology –Vivekananda College, –Tiruvedakam West Characteristics of Protozoa • Unicellular Organization – • Since Protozoa are single celled they often rely on other organisms for some necessities Reproduction: – Asexual: 1. binary fission: cytoplasmic division follows mitosis, producing two organisms 2. budding: 3. multiple fission or schizogeny: cell or organism is split into many new cells or organisms – Sexual Reproduction Symbiosis: an intimate association between two organisms Three types of symbiosis: 1. Parasitism: one organism lives in or on a second organism, called the host. – the host is harmed, but usually survives 2. Commensalism: one organism benefits and the other neither benefits nor is harmed 3. Mutualism: both organisms benefit from the relationship Protozoan Taxonomy Phylum Sarcomastigophora Subphylum Mastigophora Subphylum Sarcodina Phylum Apicomplexa Phylum Ciliophora SARCOMASTIGOPHORA Phylum Sarcomastigophora: 18,000 species, largest protozoan phylum Characteristics: 1. Unicellular or Colonial 2. Locomotion by flagella, pseudopodia, or both 3. Autotrophic, saprozoic, or heterotrophic 4. Single type of Nucleus 5. Sexual Reproduction (usually) LOCOMOTION Subphylum Mastigophora: locomotion by one or more flagella Subphylum Sarcodina: locomotion and food gathered by pseudopodia (false foot) - includes the Amoeba Pseudopodia - temporary cell extension used for movement and gathering food Types: 1. Lobopodia: broad extensions used for locomotion and engulfing food 2. Filopodia: provide constant two-way streaming that delivers food in a conveyor belt fashion 3. Reticulopodia: similar to filopodia, except they extend out and form net-like series of extensions 4. Axopodia: thin, filamentous and supported by a central axis of microtubules The AMOEBA APICOMPLEXA Phylum Apicomplexa: Characterisitics: 1. All are parasites 2. Apical Complex for penetrating host cells 3. Single type of Nucleus 4. Usually No Cilia and Flagella 5. Life cycles that typically include asexual and sexual phases Malaria caused by Plasmodium Phylum Ciliophora: Characteristics: 1. Cilia for locomotion and for the generation of feeding currents of water. 2. Relatively rigid pellicle and more or less fixed shape 3. Distinct cytostome (mouth) Structure 4. Dimorphic nuclei, typically larger macronuclei and one more smaller micronuclei Ciliophora Locomotion: cilia • Cilia are generally similar to flagella but are much shorter, more numerous and widely distributed over the surface of the organism – cilia have evolved into more specialized structures Trichocysts: used for protection, rodlike or oval structures that can be discharged and stuck to predators Trichocysts Body types Nutrition: • some ciliates possess an oral groove • cilia sweep food particles down this groove toward the cytopharynx where a food vacuole forms • some ciliates even possess an anal pore which is used to remove waste from the organism Genetic Control and Reproduction: Ciliate have two kinds of Nuclei 1. Macronuclei: large polyploid nucleus that regulates daily metabolic activities 2. Micronuclei: one or more small nucleus which are genetic reserve of the cell • • Ciliates can reproduce asexually by transverse binary fission and occasionally by budding Ciliates can reproduce sexually by conjugation Conjugation: 1. Random contact brings individuals of opposite mating types together (called conjugants) 2. Meiosis results in four haploid pronuclei 3. Three pronuclei and the macronucleus degenerate. Mitosis and mutual exchange of pronuclei is followed by fusion of the pronuclei. 4. Conjugants separate. Nuclear divisions that restore nuclear characteristics of species follow. Cytoplasmic divisions may accompany these events Conjugation