Classification of Animal Kingdom

The species in the kingdom Animalia are eukaryotic and multicellular organisms that are not having any cell wall. These organisms are heterotrophic in nature, that means they cannot prepare their food on their own. If we look at the classification of animal kingdom chart, these organisms progress from the most simplest form to the most complicated form. At one end, we observe microscopic organisms and at the other end, we observe animals that we encounter in our day today life. Aristotle is called the Father of Biology as well as Zoology.

Non-Chordates and Chordates

• The Notochord, a rod shaped cartilage kind of substance present inside the animal body, is used as one of the primary means for the classification of animal kingdom.
  
  
• The animals that do not have the Notochord inside their body are called Non-Chordates or Invertebrates.
  
  
• Non-Chordata animals include the members of the phyla Porifera, Coelenterata, Platyhelminthes, Aschelminthes, Annelida, Arthropoda, Mollusca and Echinodermata.
  
  
• The presence of Notochord inside the animal bodies during any stage of their lifespan are called Chordates.
  
  
• Phylum Chordata can further be classified into 3 different sub-phyla namely, Urochordata, Cephalochordata and Vertebrata. Urochordata and Cephalochordata are collectively called Protochordata.
  
  
• In Vertebrata, the notochord is modified into a bony and hollow vertebral column called backbone.
  
  
• Vertebrates can further be classified into two divisions namely, Agnatha and Gnathostomata. Agnatha division comprises of three Classes of animals namely, (i) Conodonta and (ii) Ostracodermi (both are extinct now) and (iii) Cyclostomata, which includes the present living jawless fishes like Hagfish and Lamprey.
  
  
• Gnathostomata division is further classified into two Superclasses namely, Pisces and Tertapoda. Superclass Pisces have 3 Classes of fishes namely, (i) Placodermi, which is extinct now, (ii) Chondrichthyes, comprising of cartilaginous fish and (iii) Osteichthyes, comprising of bony fish.
  
  
• Superclass Tetrapoda is further classified into 4 Classes of animals namely, Amphibia, Reptilia, Aves and Mammalia.