Biological Classification PDF

Aristotle’s classification It included the unicellular and the multicellular organisms - Aristotle was the earliest to attempt a more scientific basis in same group. E.g. Chlamydomonas and Spirogyra were for classification of organisms....

Aristotle’s classification It included the unicellular and the multicellular organisms - Aristotle was the earliest to attempt a more scientific basis in same group. E.g. Chlamydomonas and Spirogyra were for classification of organisms. placed under algae. - He classified plants to trees, shrubs & herbs and animals It did not differentiate between the heterotrophic fungi and into 2 groups- those with red blood & without red blood. the autotrophic green plants. Fungi have chitinous cell wall Linnaeus’s Two-kingdom classification while the green plants have cellulosic cell wall. - Linnaeus (1758) classified organisms into Two Five Kingdom Classification Kingdoms- Kingdom Plantae & Kingdom Animalia. - It is proposed by R.H. Whittaker (1969). Drawbacks of 2-kingdom classification: - It includes Monera, Protista, Fungi, Plantae & Animalia. Prokaryotes (Bacteria, cyanobacteria) and eukaryotes - This is based on cell structure, thallus organization, mode (fungi, mosses, ferns, gymnosperms & angiosperms) were of nutrition, reproduction and phylogenetic relationships. included under ‘Plants’ based on the presence of cell wall. Three-domain system: It divides Kingdom Monera into two But they are widely differed in other characteristics. domains. Eukaryotic kingdoms are included in third domain. Thus it is six-kingdom classification. Characteristics of the five kingdoms Characters Monera Protista Fungi Plantae Animalia Cell type Prokaryotic Eukaryotic Eukaryotic Eukaryotic Eukaryotic Non-cellulosic (poly- Present (Chitin & Present Cell wall Present in some Absent saccharide + amino acid) polysaccharides) (Cellulose) Nuclear membrane Absent Present Present Present Present Multicellular, Tissue/organ/ Body organisation Cellular Cellular Tissue/organ loose tissue organ system Autotrophic (photosynthetic Autotrophic Heterotrophic Heterotrophic & chemosynthetic) and Autotrophic Mode of nutrition (photosynthetic) (saprophytic or (holozoic, heterotrophic (photosynthetic) and heterotrophic parasitic) saprophytic etc.) (saprophyte/parasite) 1. KINGDOM MONERA (BACTERIA) - Bacteria are the most abundant microorganisms. II. Eubacteria (‘true bacteria’) - Hundreds of bacteria are present in a handful of soil. - They have a rigid cell wall and a flagellum (if motile). - They also live in extreme habitats such as hot springs, - They include Autotrophs (photosynthetic and deserts, snow & deep oceans. Many are parasites. chemosynthetic) and Heterotrophs. - Based on shape, bacteria are 4 types: Coccus (Spherical), a. Photosynthetic autotrophs (E.g. Cyanobacteria): Bacillus (Rod-shaped), Vibrium (Comma-shaped) & - They have chlorophyll a similar to green plants. Spirillum (Spiral). - Cyanobacteria (blue-green algae) are unicellular, colonial or filamentous, marine or terrestrial algae. - The colonies are generally surrounded by gelatinous - Some bacteria are autotrophic (synthesize food from sheath. inorganic substrates). Majority are heterotrophs (they do - They often form blooms in not synthesize food but depend on other organisms or on polluted water bodies. dead organic matter for food). - Some of them fix I. Archaebacteria atmospheric nitrogen in - They live in harshest habitats such as extreme salty areas specialized cells (heterocysts). E.g., Nostoc & Anabaena. (halophiles), hot springs (thermoacidophiles) and marshy b. Chemosynthetic autotrophs: areas (methanogens). - They oxidize inorganic substances such as nitrates, nitrites - Archaebacteria have a different cell wall structure for their & ammonia and use the released energy for ATP production. survival in extreme conditions. - They help in recycling nutrients like nitrogen, - Methanogens are present in the guts of ruminant animals phosphorous, iron and sulphur. (cows, buffaloes etc). They produce methane (biogas) c. Heterotrophic bacteria: from the dung of these animals. - They are the most abundant in nature. 1 - The majority are important decomposers. They also reproduce by a sort of sexual reproduction (DNA Impacts of Heterotrophic bacteria on human affairs: transfer from one bacterium to other). They are used to make curd from milk. Production of antibiotics. Fixing nitrogen in legume roots etc. Some are pathogens causing diseases. E.g. Cholera, typhoid, tetanus and citrus canker. Reproduction in Bacteria: Mycoplasmas are organisms without a cell wall. They are the Bacteria reproduce mainly by fission. smallest living cells. They can survive without oxygen. Under unfavourable conditions, they produce spores. Many are pathogenic in animals and plants. 2. KINGDOM PROTISTA - It includes single-celled eukaryotes. - They have two flagella, a short and a long one. - The cell contains a well-defined nucleus and other - They are photosynthetic in the presence of sunlight. In the membrane-bound organelles. Some have flagella or cilia. absence of sunlight, they behave like heterotrophs by - Protists are primarily aquatic. predating on smaller organisms. - It is a link with plants, animals and fungi. - The pigments are identical to those in higher plants. - They reproduce asexually and sexually (cell fusion and - E.g. Euglena. zygote formation). IV. Slime Moulds - Protista includes Chrysophytes, Dianoflagellates, - They are saprophytic protists. Euglenoids, Slime moulds and Protozoans. - The body moves along decaying twigs and leaves engulfing I. Chrysophytes organic material. - Found in fresh water and marine environments. - Under suitable conditions, they form an aggregation called - Microscopic and float passively in water currents (plankton). plasmodium. It may spread over several feet. - Most of them are photosynthetic. - Under unfavourable conditions, plasmodium differentiates - It includes diatoms & golden algae (desmids). and forms fruiting bodies bearing spores at their tips. - Diatoms: They have siliceous cell walls forming two thin Spores have true walls. They are highly resistant and overlapping shells, which fit together as in a soap box. The survive for many years. Spores are dispersed by air. cell wall deposit of diatoms over billions of years in their V. Protozoans habitat is known as ‘diatomaceous earth’. This is used in They are heterotrophs (predators or parasites). polishing, filtration of oils and syrups. They are the primitive relatives of animals. - Diatoms are the chief ‘producers’ in the oceans. There are 4 major groups of protozoans: II. Dinoflagellates o Amoeboid protozoans: They live in fresh water, sea - Mostly marine and photosynthetic. water or moist soil. They move and capture prey by - They appear yellow, green, brown, blue or red based on the putting out pseudopodia (false feet). E.g. Amoeba. main pigments present in their cells. Marine forms have silica shells on their surface. Some of - The cell wall has stiff cellulose plates on the outer surface. them are parasites. E.g. Entamoeba. - Most of them have 2 flagella; one lies longitudinally and o Flagellated protozoans: They are free-living or parasitic. the other transversely in a furrow between the wall plates. They have flagella. The parasitic forms cause diseases - Red dinoflagellates (E.g. Gonyaulax) undergo rapid like sleeping sickness. E.g. Trypanosoma. multiplication so that the sea appears red (red tides). They o Ciliated protozoans: They are aquatic, actively moving release toxins that kill marine animals like fishes. organisms using thousands of cilia. They have a cavity (gullet) that opens to outside. By the movement of cilia, III. Euglenoids the water with food enters gullet. E.g. Paramoecium. - Mainly fresh water organisms found in stagnant water. o Sporozoans: They have an infectious spore-like stage in - Instead of a cell wall, they have a protein rich layer called their life cycle. E.g. Plasmodium (malarial parasite). pellicle. It makes their body flexible. 3. KINGDOM FUNGI - It is a unique kingdom of heterotrophic organisms. - Some unicellular fungi (e.g. yeast) are used to make bread - Fungi are cosmopolitan. and beer. - They grow in warm and humid places. - Other fungi cause diseases in plants and animals. E.g. - E.g. mould on bread & rotten fruits, mushroom, toadstools. wheat rust-causing Puccinia. - White spots on mustard leaves are due to a parasitic fungus. - Except yeasts, fungi are filamentous. Their bodies consist - Some fungi are the source of antibiotics, e.g., Penicillium. of thread-like structures called hyphae. 2 - The network of hyphae is known as mycelium. - E.g. Mucor, Rhizopus (bread mould) and Albugo (parasitic - Hyphae are 2 types: fungi on mustard). o Coenocytic hyphae: They are continuous tubes filled II. Ascomycetes (sac-fungi) with multinucleated cytoplasm. - They are unicellular (e.g., yeast, Sacharomyces) or o Septate hyphae: They have septae or cross walls. multicellular (e.g., Penicillium). - Fungal cell wall is made of chitin & polysaccharides. - Mycelium is branched and septate. - Most fungi are saprophytes (absorb soluble organic matter - They are saprophytic, decomposers, parasitic or from dead substrates). Some are parasites. coprophilous (growing on dung). - Some live as symbionts. E.g. Lichens (fungi+ algae), - Asexual reproduction: By conidia produced exogenously mycorrhiza (fungi + roots of higher plants). on the special mycelium called conidiophores. Conidia Reproduction: germinate to produce mycelium. Vegetative propagation: By fragmentation, fission & - Sexual reproduction: By ascospores produced budding. endogenously in sac like asci (sing. ascus). The asci are Asexual reproduction: By spores such as conidia, arranged to form fruiting bodies called ascocarps. sporangiospores and zoospores. - E.g. Aspergillus, Claviceps and Neurospora. Sexual reproduction: By oospores, ascospores and - Neurospora is used in biochemical and genetic work. basidiospores. They are produced in distinct structures - Morels & truffles are edible. called fruiting bodies. III. Basidiomycetes - The sexual cycle involves 3 steps: - Includes mushrooms, bracket fungi or puffballs. a. Plasmogamy: Fusion of protoplasm between two - They grow in soil, on logs and tree stumps and in living motile or non-motile gametes. b. Karyogamy: Fusion of two nuclei. plant bodies as parasites (e.g. rusts and smuts). - The mycelium is branched and septate. c. Meiosis in zygote to give haploid spores. - The asexual spores are generally not found, but vegetative - When a fungus reproduces sexually, two haploid hyphae reproduction by fragmentation is common. of compatible mating types come together and fuse. - The sex organs are absent, but plasmogamy occurs by - In some fungi, the fusion of two haploid cells immediately fusion of two vegetative or somatic cells of different strains results in diploid cells (2n). or genotypes. The resultant structure is dikaryotic which - In ascomycetes and basidiomycetes, a dikaryotic stage or gives rise to basidium. Karyogamy and meiosis take place dikaryophase (n + n i.e. two nuclei per cell) occurs. Such in basidium producing four basidiospores exogenously. a condition is called a dikaryon. Later, parental nuclei fuse Basidia are arranged in fruiting bodies (basidiocarps). and the cells become diploid. - E.g. Agaricus (mushroom), Ustilago (smut) and Puccinia - The fungi form fruiting bodies in which reduction division (rust fungus). occurs, leading to formation of haploid spores. Based on morphology of mycelium, mode of spore formation IV. Deuteromycetes & fruiting bodies, Fungi are classified into different classes: - Commonly known as imperfect fungi because only their 1. Phycomycetes 2. Ascomycetes asexual or vegetative phases are known. 3. Basidiomycetes 4. Deuteromycetes - When perfect (sexual) stages were discovered, they were often moved to ascomycetes or basidiomycetes. I. Phycomycetes (Lower Fungi) - It is also possible that asexual and vegetative stage have - They occur in aquatic habitats and on decaying wood in been given one name placing under deuteromycetes and moist and damp places or as obligate parasites on plants. the sexual stage another name placing under another - The mycelium is aseptate and coenocytic. class. When the linkages were established, the fungi were - Asexual reproduction: By motile zoospores or by non- correctly identified and moved out of deuteromycetes. motile aplanospores. These are produced in sporangium. - They reproduce only by asexual spores (conidia). - Sexual reproduction: Zygospores are formed by fusion of - The mycelium is septate and branched. two gametes. These gametes are isogamous (similar in - Some are saprophytes or parasites. Majority are morphology) or anisogamous or oogamous (dissimilar). decomposers of litter and help in mineral cycling. - E.g. Alternaria, Colletotrichum and Trichoderma. 4. KINGDOM PLANTAE (PLANT KINGDOM) - Plants are eukaryotic chlorophyll-containing organisms - Life cycle of plants has 2 phases: Diploid sporophytic & with cellulosic cell wall. haploid gametophytic. These phases alternate with each - Some are partial heterotrophs (e.g. insectivorous plants like other. This is called alternation of generation. bladderwort & Venus flytrap) or parasites (e.g. Cuscuta). - Among different plant groups, length of the haploid & - Plantae includes algae, bryophytes, pteridophytes, diploid phases is varied. Also, these phases are free living gymnosperms and angiosperms. or dependent on others. 3  5. KINGDOM ANIMALIA (ANIMAL KINGDOM) - Animals are multicellular, heterotrophic, eukaryotic - They have a definite growth pattern and grow into adults organisms without cell wall. that have a definite shape and size. - They directly or indirectly depend on plants for food. - Higher forms show sensory and neuromotor mechanism. - They digest their food in an internal cavity and store food - Most of them are capable of locomotion. reserves as glycogen or fat. Their mode of nutrition is - The sexual reproduction is by copulation of male and holozoic (by ingestion of food). female followed by embryological development. VIRUSES, VIROIDS, PRIONS AND LICHENS - In the five-kingdom classification, acellular organisms (viruses, viroids & prions) and lichens are not mentioned. - Viruses are non-cellular and not truly ‘living’. So they are not included in five-kingdom classification. - Viruses have an inert crystalline structure outside the living cell. - Viruses are obligate parasites. - When they infect a cell, they take over the machinery of the host cell to replicate themselves, killing the host. - Louis Pasteur gave the name virus (means venom or - Viruses cause diseases like mumps, small pox, herpes, poisonous fluid). influenza & AIDS. In plants, the symptoms can be mosaic - D.J. Ivanowsky (1892) discovered virus. He recognized formation, leaf rolling and curling, yellowing and vein certain microbes that cause mosaic disease of tobacco. clearing, dwarfing and stunted growth. They were smaller than bacteria because they passed - Viroid: It is an infectious agent with a free low molecular through bacteria-proof filters. weight RNA and no protein coat. These are smaller than - M.W. Beijerinek (1898) demonstrated that the extract of viruses. It is discovered by T.O. Diener (1971). He found the infected tobacco plants cause infection in healthy plants that it caused potato spindle tuber disease. and called the fluid as Contagium vivum fluidum (infectious - Prions: These are abnormally folded protein that cause living fluid). some infectious neurological diseases. These are similar in - W.M. Stanley (1935) showed that viruses could be size to viruses. They cause bovine spongiform crystallized and crystals consist largely of proteins. encephalopathy (BSE) or mad cow disease in cattle and - A virus is a nucleoprotein, i.e., it has a protein coat its analogous variant Cr-Jacob disease (CJD) in humans. (capsid) & genetic material (RNA or DNA). LICHENS - The genetic material is infectious. - Lichens are symbiotic associations (mutually useful - No virus contains both RNA & DNA. associations) between algae & fungi. - Generally, plant viruses have single stranded RNA. Animal - The algal component is called phycobiont (autotrophic) viruses have either single or double stranded RNA or and fungal component is mycobiont (heterotrophic). double stranded DNA. Bacteriophages (viruses that infect - Algae prepare food for fungi and fungi provide shelter and bacteria) usually have double stranded DNA. absorb mineral nutrients and water for its partner. - The capsid made of small subunits (capsomeres) protects - Lichens are very good pollution indicators. They do not nucleic acid. Capsomeres are arranged in helical or grow in polluted areas. polyhedral geometric forms. MODEL QUESTIONS 1. Based on the relationship, fill in the blanks. a) Sac fungi: Ascomycetes Imperfect fungi:................................ b) Ciliated Protozoans: Paramecium Flagellated Protozoans:................................ c) Spherical shaped bacteria: …………… Rod shaped bacteria: Bacillus 2. Louis Pasteur named virus which means venom or poisonous fluid. a. Who crystallized virus for the first time? b. Name one plant disease caused by virus. 3. Arrange the organisms given in brackets under two categories, prokaryotes and Eukaryotes. (Rhizopus, Amoeba, Chlamydomonas, Nostoc, Bacteria, Yeast, Paramecium, Mycoplasma, Anabaena) 4. Select the odd man. Justify your answer. a) Chrysophytes, Dinoflagellates, Mycoplasma, Euglenoids b) Oscillatoria, Spirulina, Ascomycete, Nostoc c) Oospores, ascospores, zoospores, basidiospores 5. Differentiate between ascomycetes and basidiomycetes. 6. Viruses are not included in five-kingdom classification. Why? 4