Classification of Living Organisms Notes | SSC CGL, CHSL | IB | Railways

Classification of Living Organisms Notes | SSC CGL, CHSL | IB | Railways




Table of Contents

Hierarchy of Biological Classification

Kingdom > Phylum (for Animals) / Division (for Plants) > Class > Order > Family > Genus > Species

Classification of Kingdoms
Type of ClassificationProposed ByKingdoms
Two Kingdom ClassificationCarolus LinnaeusPlantae and Animalia
Three Kingdom ClassificationErnst HaeckelPlantae, Protista and Animalia
Four Kingdom ClassificationCopelandMonera, Protista, Plantae and Animalia
Five Kingdom ClassificationRH WhittakerMonera, Protista, Fungi, Plantae and Animalia
Six Kingdom ClassificationCarl WoeseArchaebacteria, Eubacteria, Protista, Fungi, Plantae and Animalia

Five Kingdom Classification

Robert H. Whittaker (1969) proposed the 5 kingdom classification of organisms on the basis of their cell structure, mode and source of nutrition and body organisation.

Five Kingdoms
MoneraProtistaFungiPlantaeAnimalia
Cell TypeProkaryoticEukaryoticEukaryoticEukaryoticEukaryotic
Cell WallMay be present (Polysaccharide + amino acid)Present in somePresent (chitin)Present (cellulose)Absent
Nuclear MembraneAbsentPresentPresentPresentPresent
Body OrganisationCellularCellularMulticellular / loose tissueTissue / OrganTissue / Organ / Organ System
Mode of NutritionAutotrophic (chemosynthetic or photosynthetic) or Heterotrophic (Saprophyte / Parasite)Autotrophic or HeterotrophicHeterotrophic (Saprophytes / Symbiotes)AutotrophicHeterotrophic (Holozoic / Saprophytic)
Examplesbacteria, cyanobacteria (blue-green algae), mycoplasmaunicellular algae, diatoms, protozoansyeast, mushroomsPlantsBirds, Fish, Mammals

1. Monera

  • Microscopic Organisms

2. Protista

  • Some of these use appendages such as hair-like cilia or whip-like flagella for moving around.

3. Fungi

  • Many of them have the capacity to become multicellular organisms at certain stages in their lives.
  • Some fungal species live in permanent mutually dependent relationships with cyanobacteria. Such relationship are called symbiotic.
  • Lichens can be seen as the slow growing large coloured patches on the bark of the trees.

4. Plantae

  • The first level of classification among plants depends on whether the plant body has well-differentiated distinct components, then based on whether the differentiated plant body has special tissues for the transport of water and other substances within it, further classification looks at the ability to bear seeds and whether the seeds are enclosed within fruits.
  • Plants are further divided into 5 divisions i.e., Thallophyta, Bryophyta, Pteridophyta, Gymnosperms and Angiosperms.

4.1 Thallophyta (algae)

  • Predominantly aquatic.

4.2 Bryophyta (amphibians of the plant kingdom)

  • Plant body is differentiated into stem and leaf-like structures.

4.3 Pteridophyta

  • Plant body is differentiated into roots, stem and leaf-like structures.

Thallophytes, Bryophytes and Pteridophytes have naked embryos (called as spores)

Reproductive organs of Thallophytes, Bryophytes and Pteridophytes are inconspicuous i.e., hidden reproductive organs called as cryptogamae whereas Gymnosperms and Angiosperms have well-differentiated reproductive tissues that ultimately make seeds are called as phanerogams.

4.4 Gymnosperms (gymno – naked & sperma – seed)

  • Usually perennial, evergreen and woody.

4.5 Angiosperms (angio – covered) [flowering plants]

  • The seeds develop inside an organ which is modified to become fruit.
  • Plant embryos in seeds have structures called cotyledons (aka seed leaves).
  • Angiosperms are further divided into
    • Monocots: Plants with seeds having a single cotyledon.
    • Dicots: Plants with seeds having two cotyledons.

Seeds are the result of the reproductive process. They consist of the embryo along with stored food, which serves for the initial growth of the embryo during germination.

Five Division of Plantae
ThallophytaBryophytaPteridophytaGymnospermsAngiosperms
Differentiated plant bodyNoYesYesYesYes
Specialised Vascular TissueAbsentAbsentPresentPresentPresent
Produce SeedsNoNoNoYesYes
Seeds covered by fruitsNoNoNoNoYes
ExamplesSpirogyra, Ulothrix, Cladophora and CharaMoss(Funaria), MarchantiaMarsilea, ferns, horse-tailsPines such as deodarAll flowering plants, Tomato plant

5. Animalia

  • Animalia is further divided into 10 Phylum i.e., Porifera, Coelenterata, Platyhelminthes, Nematoda, Annelida, Arthropoda, Mollusca, Echinodermata, Protochordata and Vertebrata.
Five Phylum of Animalia
SymmetryTriploblasticCoelomateNotochordExamples
PoriferaAsymmetrical / Radial SymmetryNoAcoelomateNosycon, spongilla, euplectella
CoelenterataRadial SymmetryDiploblasticAcoelomateNojellyfish, sea anemones
PlatyhelminthesBilateral SymmetryYesAcoelomateNoplanarians, liverflukes, tape worms
NematodaBilateral SymmetryYesPseudocoelomNoascaris, wuchereria
AnnelidaBilateral SymmetryYesYesNoearthworms, leeches
ArthropodaBilateral SymmetryYesYesNoprawns, butterflies, houseflies, spiders, scorpions, crabs.
MolluscaBilateral SymmetryYesYesNosnails, mussels
EchinodermataBilateral at larval stageYesYesNostarfish, sea urchins
ProtochordataBilateral SymmetryYesYesYesbalanoglossus, herdemania, amphioxus
VertebrataBilateral SymmetryYesYesYesfish, birds, humans

5.1 Porifera (organisms with holes) [sponges]

  • Non-motile animals attached to some solid support and mostly found in marine habitats.

5.2 Coelenterata

  • These are aquatic species, some of these lives in colonies (corals), while others have a solitary like-span (Hydra)

5.3 Platyhelminthes (flatworms)

  • The body is flattened dorsiventrally i.e., top to bottom, which is why these animals are called flatworms.
  • Either free living (e.g. planarians) or parasitic (e.g. liverflukes).

5.4 Nematoda

  • These are very familiar as parasitic worms causing diseases such as elephantiasis (filarial worms) or the worms in the intestines (roundworm or pinworms)

5.5 Annelida

  • These animals are found in a variety of habitats fresh water, marine water and land as well.

5.6 Arthropoda (jointed legs) (largest group of animals)

  • Open circulatory system i.e., blood doesn’t flow through blood vessels.
  • Cockroaches have a 13 chambered heart.

5.7 Mollusca

  • Open circulatory system and kidney-like organs for excretion.

5.8 Echinodermata (echinos – hedgehog, derma – skin)

  • They are exclusively free-living marine animals.
  • They also have a peculiar water-driven tube system that they use for moving around.
  • They have hard calcium carbonate structures that they use as a skeleton.

5.9 Protochordata

  • Protochordates might not have a proper notochord at all stages in their lives or for the entire length of the animal.
  • Marine animals

Notochord is a long rod-like support structure that runs along the back of the animal separating the nervous tissue from the gut. It provides a place for muscles to attach for ease of movement.

5.10 Vertebrata (Pisces, Amphibia, Reptilia, Aves, Mammalia)

  • These animals have a true vertebral column and internal skeleton
Five Classes of Vertebrata
PiscesAmphibiaReptiliaAvesMammalia
Exoskeletonscales/platesslimy skinscalesfeathershair
Respiratory Organgillsgills in larva / lungs in most adultslungslungslungs
Habitataquaticboth land & waterlandlandland
Blood Typecold bloodedcold bloodedcold bloodedwarm bloodedwarm blooded
Offspringlay eggslay eggslay eggslay eggsproduce young ones (exception: platypus, echidna)
Heart2 chambered3 chambered3 chambered (exception: crocodiles-4)4 chambered4 chambered
Examplesfishfrogs, toads, salamanderssnakes, turtles, lizards, crocodilesbirdsHuman, Cat, Bats, Rat, Whale
5.10.1 Pisces (Fish)
  • There are many kinds of fish, some with skeletons made entirely of cartilage, such as sharks and some with a skeleton made of both bone and cartilage such as tuna or rohu.
  • They obtain oxygen dissolved in water by using gills and use a muscular tail for movement.
5.10.2 Amphibia
  • These animals differ from the fish in the lack of scales, in having mucus glands in the skin, and a 3 chambered heart.
5.10.3 Reptilia
  • They lay eggs with tough coverings and do not need to lay their eggs in water, unlike amphibians.
5.10.4 Aves (Birds)
  • There is an outside covering of feathers, and two forelimbs are modified for flight.
5.10.5 Mammalia
  • They have mammary glands for the production of milk to nourish their young ones.


One thought on “Classification of Living Organisms Notes | SSC CGL, CHSL | IB | Railways

Leave a Reply

Your email address will not be published. Required fields are marked *