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| Summary |
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 In the modern system of classification, living organisms are grouped under five kingdoms, as proposed by Whittaker (1966). |
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 The Kingdom Monera includes bacteria and blue green algae, both of which possess prokaryotic cells. |
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 Bacteria are unicellular prokaryotes that have a wide distribution, in all kinds of habitats. |
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 Bacteria can be distinguished into different forms such as cocci, spirilli and vibriae. |
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 Bacterial cells may or may not have flagella. When present, the distribution of flagella varies. |
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 Bacterial cell wall is composed of murein - a peptidoglycan. |
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 Bacteria can be distinguished into autotrophs and heterotrophs based on their mode of nutrition. |
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 Bacteria generally reproduce by fission. Other processes like budding and endospore formation also occur. |
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 Sexual reproduction in bacteria involves processes like transformation and transduction. |
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 Blue green algae (cyanobacteria) represent another major group of prokaryotes. |
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 Cyanobacteria are characterised by the presence of phycocyanin (blue) and chlorophyll (green) pigments. |
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 The Kingdom Protista includes primitive unicellular eukaryotic organisms. |
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 Protista are mainly represented by unicellular algae (such as diatoms) and protozoans - rhizopods, flagellates, ciliates and sporozoans. |
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 Diatoms belong to a group called 'golden brown algae'. They have a plant body represented by a single cell called frustule. It is enclosed in two overlapping valves. |
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 Diatoms reproduce by simple cell division. Sexual reproduction also occurs and involves the formation of auxospory. |
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 Protozoans are represented by single-celled animals. They can be classified into four groups-sarcodines or rhizopods with pseudopodia, flagellates with flagella, ciliates with 'cilia' as the locomotor structures and sporozoans without locomotor structures (endoparasites). |
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 Kingdom Mycota exclusively includes the fungi. |
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 Fungi are a group of heterotrophic (saprotrophic or parasitic) primitive eukaryotes. |
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 Fungal plant body is called mycelium. It may be unicellular and multicellular. The multicellular mycelium forms filamentous structures called hyphae. |
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 Fungi reproduce by fission, budding and sexual methods. |
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 Sexual reproduction occurs by various modes such as plasmogamy and gametangial contact. |
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 Kingdom metaphyta includes the advanced group of plants such as higher algae, bryophytes and tracheophytes. |
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 Three groups of algae - green algae, red algae and brown algae are included in metaphyta. |
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 Bryophytes include a group of semi terrestrial plants. They are commonly described as 'amphibians of the plant kingdom' since they require water to complete their life cycle. |
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 The life cycle of bryophytes includes an alternation of two generations - a gametophytic generation which produces gametes and a sporophytic generation which produces spores. |
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 The adult plant body is a gametophyte. It contains reproductive structures called antheridia which produces male gametes and archegonia which produces the egg cell. |
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 The fertilised egg develops into a sporophyte which remains attached to the gametophyte, leading a parasitic life. |
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 The sporophyte produces spores which germinate to form the gametophyte. |
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 Tracheophytes include plants which are truly terrestrial and hence contain vascular tissues - xylem and phloem. |
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 Tracheophytes include three groups of advanced plants -pteridophytes, gymnosperms and angiosperms. |
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 Pteridophytes are commonly called ferns. They show a well developed plant body which is a sporophyte. |
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 The plant body contains well developed leaves called fronds. Some of the leaves are called sporophylls since they contain structures called sori. |
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 Sori enclose spore producing structures called sporangia. |
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 Sporangia release spores which germinate to produce the gametophyte. |
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 The gametophyte, which is called prothallus contains anteridia and archegonia which produce sperms and egg respectively. |
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 The zygote formed from fertilization develops into a sporophyte. |
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 Gymnosperms are a group of advanced plants which produce seeds that are not enclosed in fruits. Hence, commonly called as 'naked-seeded plants'. |
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 The adult plant body is a sporophyte which shows well developed roots, stem and leaves. |
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 The plant body produces microsporophylly containing microsporangia and megasporophylls containing megasporangia. |
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 Microsporangia produce microspores which represent the reduced gametophytic generation. Megasporangia produce megaspores (ovules) representing the reduced gametophytic generation. |
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 Angiosperms occur in diverse habitats and can be herbs, shrubs or trees. They can be annuals, biennials or perennials. |
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 Angiosperms can be broadly distinguished into dicots and monocots, which exhibit certain characteristic differences between them. |
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 The most significant aspect of angiosperm reproduction is the phenomenon of double fertilization and triple fusion. |
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 Kingdom Metazoa includes all the multicellular animals. They can be distinguished broadly into invertebrates and chordates. |
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 Invertebrates account for nearly 95% of animal Species. Chordates include the vertebrate. |
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