    Classifying organisms is called Taxonomy             Habitat - Most of the animals inhabit seas,
     (Taxis means arrangement and nomos                    fewer are seen in fresh water and even
     means method)                                         fewer on land.
    The modern taxonomic system was                      There are around 9 to 10 million animal
     developed by the Swedish botanist                     species that inhabit the earth. Only
     Carolus (Carl) Linneaeus (1707-1788). He              800,000 species are identified.
     used simple physical characteristics of
     organisms to identify and differentiate          Some important groups are listed below.
     between different species, and is based          Phylum Porifera - They are primitive
     around genetics.
                                                      organisms, most of them are salt-water
    He developed a hierarchy of groups for           sponges. They do not have organs or nerve
     taxonomy.                                        cells or muscle cells. Approximately, 8,000
    These groups are known as taxa (singular:        species exist today. e.g. Sycon, Euspongia,
     taxon).                                          Spongilla.
It is in hierarchical order:                          Phylum Coelentrata (Cnidaria) - This group
                                                      is composed of jelly-fish and other lower
     1.   Kingdom
                                                      aquatic animals. Approximately, 15,000
     2.   Phylum
                                                      species exist today. e.g. Aurelia, Adamsia.
     3.   Class
     4.   Order                                       Phylum Platyhelminthes - This group
     5.   Family                                      consists of flat worms. They inhabit both
     6.   Genus                                       marine and fresh water habitats and they are
     7.   Species                                     mostly endoparasites found in animals. e.g.
                                                      Taenia, Fascicola.
                                                      Phylum Aschelmeinthes - It is a group of
All organisms are divided into five Kingdoms:
                                                      round worms, most of them are parasites. This
1.   Animal Kingdom (Animalia)                        phylum consists of about 80,000 parasitic
2.   Plant Kingdom (Plantae)                          worms.
3.   Fungi Kingdom (Fungi)
                                                      Phylum Annelida - They are present in
4.   Protist Kingdom (Protista)
                                                      aquatic, terrestrial and are free-living or
5.   Moneran Kingdom (Monera)
                                                      parasitic in nature. This phylum comprises of
Animal Kingdom (Animalia or Metazoa)                  segmented worms. e.g. Earthworm, Leech etc.
    The word "animal" is derived from the            Phylum Arthropoda - This is the largest
     Latin word animalis which means "having          phylum which consists of insects. There are
     breath".                                         over 1 million species of insects existing
    Animals are eukaryotic, multicellular and        today. e.g. Locusts, Butterfly, Scorpion,
     heterotrophic organisms.                         Prawn.
    They      have     multiple   cells   with
                                                      Phylum Mollusca - It is the second largest
     mitochondria and they depend on other
                                                      phylum. They are terrestrial and aquatic. e.g.
     organisms for food.
                                                      Pila, Octopus.