Part two

Animals

                        The main feature on which animals are classified is the presence or absence of a vertebral column.Considering this characteristic, animals are divided into two main groups :
  

• Invertebrates
• Vertebrates

Invertebrates 

       The main phyla among invertebrates are as follows :

• Phylum 1 : Coelenterata
• Phylum 2 : Annelida
• Phylum 3 : Mollusca
• Phylum 4 : Arthropoda

Phylum 1 : Coelenterata
  
            Based on body structure, these organisms are of 2 types - Polyp form
                                                                                                    Medusa form

      Main features :
            Possesses a soft body.                                                                                                        

Jelly fish

            Has radial symmetry.
            Diploblastic body ( http://en.wikipedia.org/wiki/Diploblasty)
            Incomplete alimentary canal with only one opening.
            Lives in water.
            Has a sedentary life style.

     Examples : Hydra, Jelly fish, Sea anemone, Polyp corals

Sea anemone

Hydra

       
  

Polyp corals

Phylum 2 : Annelida

Main features :
            Metameric segmentation (http://en.wikipedia.org/wiki/Metameric)  

Leeches

            Absence of limbs
            Are of several sizes
            Some are parasitic & lives in host bodies
            Triploblastic body (http://en.wikipedia.org/wiki/Triploblastic)
            Has bilateral symmetry
            Possesses a coelom (Body cavity containing fluid)
            Possesses hard bristles called chaeta (Except in leeches)

       


Examples : Leech, Earthworm, Rag worm, Flat worms, Round worms

           

Earthworm

Flatworm

   

Rag worm

Octopus

 Phylum 3: Mollusca


Main features :                                                     
          Triploblastic body.                                  
           Unsegmented.
           Soft, wet & slimy body.
           Has bilateral symmetry.
           Possesses a coelom.

           Have well-defined circulatory, respiratory, excretory & digestive systems.

           Body comprises 3 parts :
                                                 The Head
                                                 Ventral Mascular Foot
                                                 Dorsal Visceral Hump (Mantle)
           Some have sensory tentacles.
           In some mollusca, the body has an outer shell for protection, made of Calcium Carbonate.
 

Clams

    Examples : Octopus, Cuttle Fish, Snail, Clam, Slug.

Cuttlefish

          

Snail

                                                                     



Phylum 4 : Arthropoda

                      This phylum contains more species than any other phyla.More than 3/4 of all known species of animals are arthropods.The most abundant arthropods are insects.

Main features :
         
        Possesses joint appendages- These are more elaborate & specialized than in annelids.
        Shows clear metameric segmentation.                                

Dragonfly

        Possesses hard, chitonous exoskeleton.
        Triploblastic body.
        Coelomate.
        Has bilateral symmetry.
        Lives in water as well as land.





Examples : Scorpion, Butterfly, Dragonfly, Cockroach, Prawns, Millipedes, Ticks

Arthropods