biological classification

• Earliest Attempt at classification was by Aristotle
• Aristotle's classification

  • Plants
  • Animals
• Aristotle's classification of Animals

  • Trees, shrubs & herbs
  • Red blood (have RBCs)
  • Non-red blood (No RBC)
• 2 kingdom classification

  Plants & Animals
• Drawbacks of Aristotle's classification: Did not distinguish between prokaryotes & eukaryotes, photosynthetic & non-photosynthetic, unicellular & multicellular
• 5 Kingdom Classification

  Proposed by RH Whittaker (1969) based on mode of reproduction, phylogeny, cell type, and body organisation
• Fungi were earlier part of the Plant kingdom, but were later moved to their own separate kingdom
• Fungi

  Heterotrophic, cell wall made of chitin
• Blue Green Algae (BGA) or Cyanobacteria

  Autotrophic, plant cell wall made of cellulose, earlier part of Monera kingdom, now moved to Plantae kingdom
• BGA are prokaryotes while plants are eukaryotes
• 3 Domain System

  Archaea, Bacteria, Eukaryota (Protista, Plantae, Animalia, Fungi)
• Characteristics of Monera (Bacteria & Mycoplasma)

  • Prokaryotic
  • Unicellular
  • No cell wall
  • Smallest cell size
  • Can survive without O2
• Bacteria

  • Most diverse in terms of nutrition (photoautotrophic, chemoautotrophic, heterotrophic)
  • Varied shapes (cocci, bacilli, spirilla, vibrio)
• Types of Bacteria

  • Archaebacteria (autotrophic, live in extreme conditions)
  • Eubacteria (heterotrophic)
• Cyanobacteria (BGA)

  Unicellular, photosynthetic, can form colonies or filaments, similar to plants
• Cyanobacteria

  • Contain chlorophyll and chromatophores
  • Have specialized structures like heterocysts and gas vacuoles
  • Rapid growth can lead to algal blooms and body is covered by mucilagenous sheath
• Chemoautotrophic Bacteria

  Oxidise chemicals to obtain energy and synthesize ATP, help in mineral recycling
• Heterotrophic Bacteria

  Act as decomposers, involved in nitrogen fixation, production of antibiotics, curd making, and causing diseases
• Modes of Bacterial Reproduction

  • Binary fission
  • Endospore formation (in unfavourable conditions)
• Bacteria can also reproduce through conjugation, a form of sexual reproduction involving transfer of genetic material
• Protista


  Kingdom with boundaries not well defined, show similarities with plants, animals, fungi, and bacteria
• Fungi

  Heterotrophic, cell wall made of chitin, grow in warm and moist places, include saprophytes and parasites
• Types of Fungi

  • Saprophytes (bread mould, mushrooms)
  • Parasites (Albugo, Puccinia, Ustilago)
  • Symbiotic (Lichens, Mycorrhiza)
• Fungi

  • Network of hyphae called mycelium, reproduce asexually by spores and sexually by fusion of hyphae
• Classification of Fungi

  • Based on type of mycelium, type of fruiting body, and mode of spore formation
• Lichens are a symbiotic association between algae (phycobiont) and fungi (mycobiont)
• Viruses are non-cellular, have genetic material (DNA or RNA) and a protein coat, and are obligate parasites
• Viroids

  Smaller than viruses, have only RNA and no protein coat
• Prions


  Misfolded proteins that can transmit their misfolded shape, cause diseases like Bovine Spongiform Encephalopathy (mad cow disease)
• chrysophytes :

  • diatoms and desmuds (golden alage)
  • fresh water or marine water
  • plankton ( passive floating- move with water current)
  • microscopic and photosynthetic
• diatoms :

  • chief producers of oceans
  • 2 thin overlapping shells : soap box
  • wall made up of silica which is indestructible
  • dead diatoms - cell wall deposit in the bottom of the sea called diatomaceous earth
  • diatomaceous earth is used for polishing, filtration of oil and syrup and sound proof room or walls
• dinoflagellates :

  • 2 flagella - transverse and longitudinal
  • red sea - trichodesmium (algae)
  • mostly marine
  • photosynthesis - different pigments - different colours
  • cell wall is a stiff cellulose plate
  • gonyaulax causes red tides (rapid multiplication)
  • release toxins - saxi toxin (kills marine animals and fishes)
• euglenoids :

  • body covered by pellicle - protein (makes body flexible)
  • eye spot has photoreceptor
  • 2 flagella long and short
  • contractile vacuole is for excretion
  • mixotropic nutrition: phototrophic in presence of sunlight, pigments identical to higher plants
  • heterotropic : in absence of sunlight, feeds on other organisms
• slime moulds :

  • saprophytic
  • grow on dead and decaying trees , twigs and leaves
  • under favourable conditions - plasmodium -> no cell wall
  • under unfavourable conditions: fruiting bodies bearing spores having true cell wall, extremely resistant and dispersal of spores by air currents
  • e.g : physarum
• amoeboid :

  • ameoba (free living) entamoeba (parasite)
  • pseudopodia ( false feet)
  • marine form have silica shell
• ciliated :

  • paramoecium
  • have thousands of cilia
  • gullet : a cavity that opens to outside of cell surface and helps in uptake of food
• flagellated :

  • have flagella
  • parasitic: trypanosoma
  • trypanosoma causes sleeping sickness and vector causing it is tse-tse fly
• sporozoans : infectious spore like stage form in their life cycle

  • e.g : plasmodium - malaria parasite and vector is mosquito
• fungi is multicellular except for yeast
• parasites of fungi :

  1. albugo candida : causes white spots on mustard leaves
  2. puccinia graninis : rust of wheat
  3. ustilago trifici : smut of wheat