Chapter-2
Biological Classification
Systems of Classification :
- Earliest classification was given by Aristotle. Divided plants into herbs, shrubs and trees.
Animals into those with red blood and those who do not have it. - Two Kingdom Classification : Given by Carolus Linnaeus-Kingdom-Plantae and Kingdom-Animalia.
- Five Kingdom Classification : By R.H. Whittaker, Monera, Protisa, Fungi, Plantae and Animalia are the five kingdoms.
- The main criteria for classification of organisms into five kingdoms include cell structure, thallus organisation, mode of nutrition, reproductionn and phylogenetic relationships.
Kingdom Monera :
- Has bacteria as sole members.
- Cell wall made up of peptidoglycan.
- Bacteria can have shapes like: Coccus (spherical), Bacillus (rod-shaped), Vibrium (comma shaped) and spirillum (spiral shaped).
- Bacteria found almost everywhere and can be Photosynthetic autorophs, Chemosynthetic autotrophs or Heterotrophs.
- Archaebacteria
- Halophiles (salt-loving)
- Thermoacidophiles (in hot springs)
- Methanogens (in marsh and in gut of ruminant animals. Produce methane gas.)
- Eubacteria
- Photosynthetic autotrophs like Cyanobacteria (Blue-green algae BGA).
Some like Anabaena and Nostoc have specialized cells heterocysts for nitrogen fixation. - Algae bloom is rich growth of blue green algae over the surface of polluted water bodies.
- Algae bloom releases neurotoxins, deplete oxygen and makes water unfit for use.
- Chemosynthetic autotrophs : Oxidise various inorganic substances like nitrates/nitrites, ammonia and use released energy for their ATP production. They helps in nutrients recycling of N,P, Fe and S.
- Heterotrophs Bacteria : Decomposers help in making curd, production of antibotic, N2 fixation, casuse diseases like cholera, typhoid, tetanus and citrus canker.
Mycoplasmas : Completely lack cell well. Smallest living cells. Can survive without oxygen. Pathogenic in animals and plants.
- 1. It utilise one or two morophological trial.
- 2. Homology is never standard.
- 3. The system does not employ characters from anatomy cytology, biochemistry, genetics etc. for grouping of organisms.
- 1. The system employs several morophological characters for grouping organism.
- 2. It studies homology in all characters including morphology, anatomy etc.
- 3. This system gives information about both Natural relationships and phylogeny.
- 1. It was proposed by Engler and Prantl. They arranged flowering plants according to increasing complexity of their floral morphology.
- 2. It was based on possible evolution of different traits.
- 1. Lichen with dual mode.
- 2. Fungi remain fixed but nutrients saprophytic.
- 3. No distribution of unicellular and multicellular organism.
- 4. No distribution of prokaryotic and eukaryotic organisation.
- 5. Euglena can move as well as can do Photosynthesis.
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(Comprises of all single celled eukaryotes)
- Forms a link between plants, animals and fungi.
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(i) Chrysophytes (Has diatoms and golden algae/desmids)
- Chief producers in Ocean.
- Cell walls have silica which makes it indestructible and cell walls overlap to fit together like a soap box.
- Their accumlation forms 'Diatomaceous Earth' (gritty soil)
- Used in polishing, filtration of oils and syrups.
Fresh water/marine, photosynthetic, microscopic plankton.
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(ii) Dinoflagellates :
- Marine, photosynthetic, cell wall has stiff cellulose plates.
- Two flagella-one logitudinal and other transverse in a furrow between wall plates.
- Example : Gonyaulaz multiples rapidly, make sea appear red (red tides) and produce toxins to kill marine animals.
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(iii) Euglenoids :
- Found in stagnant fresh water.
- Photosynthetic in presence of sunlight but becomes heterotrophs if they do not get sunglight. (Mixotrophic nutrition)
- Example : Euglena
- (iv) Protozoans : Are heterotrophs and live as parasites. Have four major groups.
- (v) Amoeboid : Catch prey using pseudopodia, e.g. Amoeba, Entamoeba are parasite.
- (vi) Flagellated : Have one or more flagella. Cause diseases like Sleeping Sickness e.g., trypanosoma.
- (vii) Ciliated : Have clilia to move food into gullet and help in locomotion. e.g., Paramoecium
- (viii) Sporozoans : Have infective spore like stage in life cycle, e.g., Plasmodium which causes malaria.
- 1. Heterotrophic organisms
- 2. Non chlorpohyllous hyphae
- 3. Network of hyphae called mycelium
- 4. Hyphae which have multinucleated cytoplasm are called coenocytic hyphae
- 5. Cell wall of chitin and polysaccharides
- 6. Cosmopolitan, Grow in warm and humid places.
- 7. Saprophytic, parasitic, symbiotic (Lichen and Mycorrhiza) e.g., Puccinia, (wheat rust disease), Penicillium, Yeast (unicellular fungus).
- 8. Reproduction can take place by vegetative means fragmentation, fission and budding. Asexual reproductionn by spores-conidia, sporangiospores or zoospores. Sexual reproductionn by oospores, ascospores and basidiospores-produced in fruiting bodies.
- 9. Sexual cycle involves 3 steps :
- (i) Plasmogamy (fusion of Protoplasms.)
- (ii) Karyogamy (fusion of two nuclei.)
- (iii) Meiosis in zygote resulting in haploid spores.
- 10. Dikaryophase is a condition of having dikaryon in an intervening dikaryotic stage (n + n i.e., two nuclei per cell) between plasmogamy and karyogamy in fungi like ascomycetes and basidiomycetes.
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(i) Phycomycetes :
- Grow on decaying wood or as obligate parasites on plants.
- Mycelium aseptate and coenocytic.
- Spores produced endogenously in sporangium.
- Asexual reproductionn by Zoospores or Aplanospores
- Zygospores are formed by the fusion of gametes.
e.g., Rhizopus, Albugo, Mucor
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(ii) Ascomycetes :
- Also known as 'sac fungi'
- Are saprophytic, decomposers, parasitic or coprophilous (growing on dung).
- Mycelium branched and septate
- Asexual spores are called conidia produced exogenously on the conidiophores.
- Sexual spores are called ascospores produced endogenously in ascus, produced inside fruiting body called Ascocarp.
e.g., Aspergillus, Neurospora, Saccharomyces (Unicelluar fungi), Claviceps, morels, truffles
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(iii) Basidiomycetes :
- Mycelium septate and branched.
- Generally asexula spores are not found.
- Vegetative reproductionn by fragmentation.
- Sexual reproductionn by fusion of vegetative or somatic cells to form basidium produced in basidiocarp.
- Basidium produces four basidiospores exogenously after meiosis.
e.g., Agaricus, Ustilago, Pucccinia
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(iv) Deuteromycetes :
- Called as 'Fungi Imperfecti' as sexual form (perfect stage) is not known for them.
- Once sexual form is discovered the member is moved to Ascomycetes or Basidiomycetes.
- Mycelium is septate and branched.
- Are saprophytic parasitic or decomposers.
e.g., Alternaria, Colletotrichum, Trichoderma.
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Viruses :
- They did not find a place in biological classification.
- Not truly living.
- Non-cellular organisms which take over the machinery of host cell on entering it and becomer living bust as such they they have inert crystalline structure appear non-living. So, diificult to call them living or non-living.
- Virus means venom or poisonous fluid. Pasteur gave the term 'Virus'.
- D.J, Ivanowsky found out that certain microbes caused Tobacco Mosaicn Disease in tobacco plant.
- M.W. Beijerinek called as 'Contagium vivum fluidum' as extracts of infected plants of tobacco could causes infection in healthy plants.
- W.M. Stanely showed viruses could be crystallized to form crystals of protein which are inert outside their specific host.
- Viruses are obligate parasites.
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Structure of Virus :
- It is a nuclesprotein made up of protein coat called Capsid. Capsid is made up of capsmeres arranged in helical of polyhedral-geometric forms. Have either DNA OR RNA as genetics material which may be single or double stranded.
- Usually plant viruses have single stranded RNA; bacteriophages have double stranded DNA and animal viruses have single or double stranded RNA or double stranded DNA.
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Diseases Caused in Humans :
- Mumps, Small pox, herpes, influenza and AIDS etc. In plants, symptoms can be mosaic formation, leaf rolling and curling, yellowing and vein clearing, dwarfing and stunted growth.
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Viroids :
- Infectious agent, free RNA (lack protein coat)
- RNA has low molecular weight.
- Causes potato spindle tuber disease.
- Discovered by T.O. Diener.
- They are highly resistant glycoproteins molecular which function as infectious agent.
- Symbiotic association between algal component (Phycobiont) and fungal component (mycobiont). Algae provides food. Fungi provides shelter and absorb nutrients and water for alga.
- Good pollution indicators as they do not grow in polluted areas.
Prions :
Lichens :
