Classification HistoryThe earliest classification was done byAristotle. He used simple morphologicalcharacters to classify plant into trees,shrubs & herbs. He also divided animalsinto two groups, those who poses redblood and those who did not.
Classification HistoryLinnaeus classified living worldinto Two kingdom. Plantae andAnimalia.This system was used tillvery recently. This system does notdistinguish between Eukaryotic andprokaryotic ,unicellular andmulticellular organisms andphotosynthetic (green algae) andnon-photosynthetic (fungi)organisms.
5 Kingdom ClassificationR.H. Whittaker (1969) proposed a FiveKingdom Classification. The kingdomsdefined by him were named Monera,protista, Fungi, Plantae and Animalia. Themain criteria for classification used by himinclude cell structure, thallus organisation,mode of nutrition, reproduction andphylogenetic relationships. .
All prokaryotic organisms were grouped togetherunder Kingdom Monera and the unicellulareukaryotic organisms were placed in Kingdomprotista. Kingdom Protista has brought togetherChlamydomonas, Chlorella (earlier placed in Algaewithin Plants and both having cell walls) withParamoecium and Amoeba (which were earlierplaced in the animal kingdom which lack cell wall).It has put together organisms which, in earlierclassifications, were placed in different kingdoms.
Living worldMoneraProtista FungiPlantaeAnimalia
Kingdom MoneraBacteria mainly comprises of the Kingdom Monera. They are the mostabundant micro-organisms. They live in extreme habitats such as hotsprings, deserts, snow and deep oceans .Many of them live in or on otherorganisms as parasites.Bacteria are grouped under four categories based on their shape thespherical Coccus , the rod-shaped Bacillus , the comma shaped Vibrium andthe spiral Spirillum Some of the bacteria are autotrophic, i.e., they synthesisetheir own food from inorganic substrates. They may be photosyntheticautotrophic or chemosynthetic autotrophic. The vast majority of bacteriaare heterotrophs,i.e., they do not synthesise their own food but depend onother organisms or on dead organic matter for food.Back NextSlide 9
These bacteria are live in the most harsh habitats such asextreme salty areas (halophiles), hot springs(thermoacidophiles) and marshy areas(methanogens). Archaebacteria differ from otherbacteria in having a different cell wall structure and thisfeature is responsible for their survival in extremeconditions. Methanogens are present in the gut of severalruminant animals such as cows and buffaloes and theyare responsible for the production of methane (biogas)from the dung of these animals.ArchaebacteriaNext
EubacteriaThere are thousands of different eubacteria or ‘true bacteria’. They arecharacterised by the presence of a rigid cell wall, and if motile, aflagellum. Some of these organisms can fix atmospheric nitrogen inspecialised cells called heterocysts, e.g., Nostoc and Anabaena. Theyplay a great role in recycling nutrients like nitrogen, phosphorous, ironand sulphur.Heterotrophic bacteria are the most abundant in nature. The majorityare important decomposers. Many of them have a significant impacton human affairs. They are helpful in making curd from milk,production of antibiotics, fixing nitrogen in legume roots, etc. Someare pathogens causing damage to human beings, crops, farm animalsand pets. Cholera, typhoid, tetanus, citrus canker are well knowndiseases caused by different bacteria.Bacteria Growth mainly by fission (Figure 2.3). Sometimes, underunfavourable conditions, they produce spores. They also reproduce by a sortof sexual reproduction by adopting a primitive type of DNA transfer from onebacterium to the other.Next
The Mycoplasma are organisms that completely lack a cellwall. They are the smallest living cells known and can survivewithout oxygen. Many mycoplasma are pathogenic in animals andplants.Dividing BacteriumBack
Kingdom ProtistaAll single-celled eukaryotes are placed underProtistaMembers of Protista are primarily aquatic.This kingdom forms a link with the others dealingwith plants, animals and fungi. Being eukaryotes,the protistan cell body contains a well definednucleus and other membrane-bound organelles.Protists reproduce asexually and sexually by aprocess involving cell fusion and zygote formation.Next
ChrysophytesThis group includes diatoms and golden algae (desmids). They arefound in fresh water as well as in marine environments. They aremicroscopic and float passively in water currents (plankton). Most of them are photosynthetic.Triceratium PinnulariaNext
DinoflagellatesThese organisms are mostly marine and photosynthetic.Theyappear yellow, green, brown, blue or red depending on themain pigments present in their cells. The cell wall has stiffcellulose plates on the outer surface. Most of them have twoflagella. Very often, red dinoflagellates(Example: Gonyaulax)undergo such rapid multiplicationthat they make the seaappear red (red tides). Toxins released by such large numbersmay even kill other marine animals such as fishes.Red TidesNext
EugelenoidsEugelenoids are fresh water organisms found in stagnant water. Instead of acell wall, they have a protein rich layer called pellicle which makes theirbody flexible. Though they are photosynthetic in the presence of sunlight,when deprived of sunlight they behave like heterotrophs by predating onother smaller organisms. Interestingly, the pigments of euglenoids areidentical to those present in higher plants. Example: EuglenaNext
Slime MouldsSlime moulds are saprophytic protists. The bodymoves along decaying twigs and leaves engulfingorganic material.Eg.plasmodium.PlasmodiumNext
ProtozoansAll protozoans are heterotrophs and live aspredators or parasites. They are believed to beprimitive relatives of animals. There are fourmajor groups of protozoans.Next
Types of Protozoans:-Amoeboid Protozoans: Theseorganisms live in fresh water, seawater or moist soil. They moveand capture their prey by puttingout pseudopodia (false feet) as inAmoeba. Some of them such asEntamoeba are parasites.Flagellated Protozoans: Themembers of this group are eitherfree-living or parasitic. They haveflagella. The parasitic forms causediseases such as sleeping sickness.Example: Trypanosome.AmoebaTrypanosomeNext
Types of Protozoans:-Ciliated protozoans: These areaquatic, actively moving organismsbecause of the presence of thousandsof cilia. They have a cavity (gullet) thatopens to the outside of the cellsurface. Example: ParamoeciumSporozoans: This includes diverseorganisms that have an infectiousspore-like stage in their life cycle. Themost notorious is Plasmodium(malarial parasite) which causesmalaria which has a staggering effecton human population ParamoeciumExit
Kingdom FungiThe fungi constitute a unique kingdom of heterotrophicorganisms. They show a great diversity in morphologyand habitat. Most fungi are heterotrophic and absorb solubleorganic matter from dead substrates and hence are calledsaprophytes. Those that depend on living plants and animalsare called parasites. They can also live as symbionts – inassociation with algae as lichens and with roots of higherplants as mycorrhiza.Reproduction in fungi can take place byvegetative means – fragmentation, fission and budding.Asexual reproduction is by spores called conidia orsporangiospores or zoospores, and sexual reproduction is byoospores, ascospores and basidiospores.Next
PhycomycetesMembers of phycomycetes arefound in aquatic habitats and ondecaying wood in moist and dampplaces or as obligate parasites onplants. The mycelium is aseptate andcoenocytic. Asexual reproduction takesplace by zoospores (motile) or byaplanospores (non-motile). Somecommon examples are Mucor Rhizopus(the bread mould mentioned earlier)and Albugo (the parasitic fungi onmustard).MucorNext
AscomycetesCommonly known as sac-fungi, the ascomycetes aremostly multicellular, e.g.,Penicillium rarely, orunicellular, e.g., yeast(Saccharomyces) . They aresaprophytic, decomposers,parasitic or coprophilous(growing on dung). Myceliumis branched and septatePenicilliumNext
BasidiomycetesCommonly known forms ofbasidiomycetes aremushrooms, bracket fungi orpuffballs. They grow in soil,on logs and tree stumps andIn living plant bodies asparasites, e.g., rusts andsmuts. The mycelium is branchedand septate. Some commonmembers are Agaricus(mushroom) , Ustilago (smut)and Puccinia (rust fungus).AgaricusPucciniaNext
DeuromycetesCommonly known as imperfect fungi because onlythe asexual or vegetative phases of these fungi areknown. When the sexual forms of these fungi werediscovered they were moved into classes theyrightly belong to. Some members are saprophytesor parasites while a large number of them aredecomposers of litter and help in mineral cycling.Some examples are Alternaria, Colletotrichum andTrichoderma.Exit
LichensLichens are symbiotic associations i.e. mutually usefulassociations, between algae and fungi. The algalcomponent is known as phycobiont and fungalcomponent as mycobiont, which are autotrophic andheterotrophic, respectively. Algae prepare food forfungi and fungi provide shelter and absorb mineralnutrients and water for its partner. So close is theirassociation that if one saw a lichen in nature onewould never imagine that they had two differentorganisms withinthem. Lichens are very good pollutionindicators – they do not grow in polluted areas.Lichens
Kingdom PlantaeKingdom Plantae includes all eukaryoticchlorophyll-containing organismscommonly called plants. A few membersare partially heterotrophic such as theInsectivorous plants or parasites. Theplant cells have an eukaryotic structure withprominent chloroplasts and cell wall mainlymade of cellulose. Plantae includes algae,bryophytes, pteridophytes, gymnospermsand angiospermsExit
Kingdom AnimaliaThis kingdom is characterised by heterotrophiceukaryotic organisms that are multicellular andtheir cells lack cell walls. They directly orindirectly depend on plants for food. Theydigest their food in an internal cavity and storefood reserves as glycogen or fat. Most of themare capable of locomotion.Exit
Virus & ViroidsIn the five kingdom classification of Whittakerthere is no mention of some cellular organisms like virusesand viroids.The viruses are non-cellular organisms that arecharacterised by having an inert crystalline structureoutside the living cell. Once they infect a cell they take overthe machinery of the host cell to replicate themselves,killing the host. The name virus that means venom orpoisonous fluid was given by Pasteur. D.J. Ivanowsky(1892) . viruses also contain genetic material, that could beeither RNA or DNA. No virus contains both RNA and DNA. Avirus is a nucleoprotein and the genetic material isinfectious. Viruses cause diseases like mumps, small pox,herpes and influenza. AIDS in humans is also caused by avirus. In plants, the symptoms can be mosaic formation,leaf rolling and curling, yellowing and vein clearing,dwarfing and stunted growth.Tobacco mosaic virus
• Viroids: In 1971 T.O. Diener discovered a newinfectious agent that was smaller than virusesand caused potato spindle tuber disease. It wasfound to be a free RNA; it lacked the protein coatthat is found in viruses, hence the name viroid.The RNA of the viroid was of low molecularweight.BacteriophageT.O. Diener