Methods of grouping animals

There are several ways of grouping animals. In all these methods the

basic Taxon remains without any change. However the taxa are rearranged in different groups. All these groupings are mostly provided for the convenience in identifying similar taxa.

I. One of the earliest method of grouping the animals could be dividing the Animal kingdom into two assemblages called Invertebrata and  Vertebrata This scheme was provided initially by Aristotle. This scheme does not have a place for the Prochordates.

II.  Animals  can  also  be  grouped  as   single  celled  and  multicellular.  Thesingle celled organisms are called the Protozoans . The multicellular could be called the  Metazoans. In this arrangement among the metazoans the unique nature of the sponges in not having a tissue grade of body constuction is notmentioned.

III.  In  yet  another  method  the  animals  are  grouped  under  following  three assemblages.

1.  Protozoa - single celled animals

2. Parazoa - Multicellular without tissue grade (sponges).

3. Eumetazoa - Multicellular with tissue grade.Eumetazoa

  is  a  large  group  including  most  of  the  multicellular animals. Hence it is subdivided further into two groups.

1. Diploblastic animals - having ectoderm and   entoderm as two layers in the body wall. Ex : Coelenterata.

2. Triploblastic animals - having ectoderm, mesoderm and endoderm as three layers in the body wall. The Triploblastic animals are further divided into three groups based on the presence or absence of an embryonic body cavity called coelom.

1. Acoelomata - no coelom Ex : Platyhelminthes

2. Pseudocoelomata - with a false coelom Ex : Nematoda

3. Coelomata - with a true coelom

IV. In a recent system, the entire living world is subdivided into 5 kingdoms.This  system  is  much  more  broader  including  algae,  fungi,  and  plants.  It  is known  as  the  Five  kingdom  concept.

1. Kingdom :  Monera  -  It  includes  all  bacteria  and  the  cyanobacteria.  Acircular  DNA  occurs  in  the  cytoplasm.  The  cell  wall  is  a  rigid  structure.

a) Phylum :Cyanobacteria b) Phylum : Bacteria.

2. Kingdom : Protoctista or Protista - It includes single celled eukaryotes. Ithas two subkingdoms, namely Protozoa and Algae.

3. Kingdom : Fungi

4. Kingdom : Plantae (green plants)

5. Kingdom : Animalia : multicellular, eukaryotic animals.

Major phyla Phylum : Protozoa This phylum includes a great diversity of small, microscopic organ- isms.  These  are   single  celled  eukaryotes.  Their  locomotion  happens  using pseudopodia, cilia or flagella.

1. Kingdom  :  Monera  -  It  includes  all  bacteria  and  the  cyanobacteria.  A circular  DNA  occurs  in  the  cytoplasm.  The  cell wall  is  a  rigid  structure.

a) Phylum :Cyanobacteria

 b) Phylum : Bacteria.

2. Kingdom : Protoctista or Protista - It includes single celled eukaryotes. Ithas two subkingdoms, namely Protozoa and Algae.

3. Kingdom : Fungi

4. Kingdom : Plantae (green plants)

5. Kingdom : Animalia: multicellular, eukaryotic animals. Major phyla