Biology Classification (Class 11)

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1. Introduction to Classification Need for Classification: To organize the vast diversity of life forms, study them systematically, and understand their interrelationships. Early Systems: Aristotle: Classified plants (trees, shrubs, herbs) and animals (red blood / no red blood). Carolus Linnaeus: Developed two-kingdom classification (Plantae, Animalia) and binomial nomenclature. 2. Two Kingdom Classification Proposed by: Carolus Linnaeus Kingdoms: Plantae and Animalia Limitations: Did not distinguish between prokaryotes and eukaryotes. Did not distinguish between unicellular and multicellular organisms. Did not distinguish between photosynthetic (algae) and non-photosynthetic (fungi) organisms. Fungi, Euglena, etc., were difficult to classify. 3. Five Kingdom Classification Proposed by: R.H. Whittaker (1969) Criteria Used: Cell structure (prokaryotic/eukaryotic) Body organization (unicellular/multicellular) Mode of nutrition (autotrophic/heterotrophic) Reproduction Phylogenetic relationships Kingdoms: Monera, Protista, Fungi, Plantae, Animalia 4. Kingdom Monera Organisms: All prokaryotes (bacteria, cyanobacteria, mycoplasma). Cell Type: Prokaryotic. Cell Wall: Non-cellulosic (polysaccharide + amino acid). Body Organization: Unicellular. Mode of Nutrition: Autotrophic (chemosynthetic or photosynthetic) and Heterotrophic (saprophytic or parasitic). Reproduction: Asexual (binary fission), sexual (conjugation, transformation, transduction). Examples: E. coli , Nostoc , Mycoplasma. Bacteria Classification: Shape: Coccus (spherical) Bacillus (rod-shaped) Vibrio (comma-shaped) Spirillum (spiral-shaped) Nutrition: Autotrophic: Photosynthetic (e.g., Cyanobacteria/Blue-green algae), Chemosynthetic. Heterotrophic: Decomposers, pathogens. Archaebacteria: Live in extreme environments (halophiles, thermoacidophiles, methanogens). Eubacteria: "True bacteria," rigid cell wall, flagellum if motile. 5. Kingdom Protista Organisms: All single-celled eukaryotes. Cell Type: Eukaryotic. Cell Wall: Present in some (e.g., diatoms), absent in others. Body Organization: Unicellular. Mode of Nutrition: Autotrophic (photosynthetic), Heterotrophic (saprophytic, parasitic, holozoic). Reproduction: Asexual and sexual (cell fusion, zygote formation). Examples: Amoeba, Euglena, Paramecium, Diatoms. Groups of Protista: Chrysophytes: Diatoms, desmids; photosynthetic; cell walls with silica. Dinoflagellates: Marine, photosynthetic; two flagella; 'red tides'. Euglenoids: Fresh water, lack cell wall, two flagella, photosynthetic (in light) or heterotrophic (in dark). Slime Moulds: Saprophytic protists; form plasmodium under favorable conditions. Protozoans: Heterotrophic; Amoeboid (e.g., Amoeba) Flagellated (e.g., Trypanosoma) Ciliated (e.g., Paramecium) Sporozoans (e.g., Plasmodium) 6. Kingdom Fungi Organisms: Heterotrophic eukaryotes. Cell Type: Eukaryotic. Cell Wall: Present, made of chitin and polysaccharides. Body Organization: Multicellular (except yeast, which is unicellular). Filaments called hyphae, forming mycelium. Mode of Nutrition: Heterotrophic (saprophytic or parasitic), symbiotic (lichens, mycorrhiza). Reproduction: Vegetative: Fragmentation, fission, budding. Asexual: Spores (conidia, sporangiospores, zoospores). Sexual: Spores (oospores, ascospores, basidiospores) through plasmogamy, karyogamy, meiosis. Examples: Yeast, Penicillium, Mushrooms, Rusts, Smuts. Classes of Fungi: Phycomycetes: Aquatic habitats, moist/damp places; asexual zoospores/aplanospores; sexual zygospores. (e.g., Mucor , Rhizopus , Albugo ). Ascomycetes (Sac Fungi): Unicellular (yeast) or multicellular; asexual conidia; sexual ascospores in ascocarps. (e.g., Aspergillus , Claviceps , Neurospora ). Basidiomycetes (Club Fungi): Mushrooms, bracket fungi, puffballs; asexual spores generally absent; sexual basidiospores in basidiocarps. (e.g., Agaricus , Ustilago , Puccinia ). Deuteromycetes (Imperfect Fungi): Only asexual or vegetative phases known; saprophytic or parasitic; great decomposers. (e.g., Alternaria , Colletotrichum , Trichoderma ). 7. Kingdom Plantae Organisms: All eukaryotic chlorophyll-containing organisms. Cell Type: Eukaryotic. Cell Wall: Present, made of cellulose. Body Organization: Multicellular. Mode of Nutrition: Autotrophic (photosynthesis). Some are partially heterotrophic (e.g., insectivorous plants like Venus flytrap, Cuscuta). Reproduction: Asexual and sexual (alternation of generations: sporophytic and gametophytic phases). Examples: Algae, Bryophytes, Pteridophytes, Gymnosperms, Angiosperms. 8. Kingdom Animalia Organisms: All multicellular heterotrophic eukaryotes. Cell Type: Eukaryotic. Cell Wall: Absent. Body Organization: Multicellular, complex tissue and organ systems. Mode of Nutrition: Heterotrophic (holozoic); ingest food and digest internally. Reproduction: Mostly sexual. Examples: Insects, fish, birds, mammals. 9. Viruses, Viroids, Prions, Lichens Viruses: Non-cellular, obligate intracellular parasites. Genetic material (DNA or RNA) + protein coat (capsid). Link between living and non-living. (e.g., Tobacco Mosaic Virus, HIV). Viroids: Discovered by T.O. Diener (1971). Smaller than viruses, contain only free RNA (no protein coat). Cause plant diseases (e.g., potato spindle tuber disease). Prions: Abnormally folded proteins. Cause neurological diseases (e.g., Mad Cow Disease, Creutzfeldt-Jakob disease). Lichens: Symbiotic association between algae (phycobiont, autotrophic) and fungi (mycobiont, heterotrophic). Pioneer species on bare rocks, pollution indicators. 10. Three-Domain System (Six Kingdom Classification) Proposed by: Carl Woese (1977) Domains: Archaea, Bacteria, Eukarya. Kingdoms: Domain Archaea: Kingdom Archaebacteria Domain Bacteria: Kingdom Eubacteria Domain Eukarya: Kingdom Protista, Kingdom Fungi, Kingdom Plantae, Kingdom Animalia Based on ribosomal RNA (rRNA) gene sequencing.