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. The nutrition is either autotrophic or heterotrophic. They reproduce either  asexually  or  by  sexual  methods.  Ex  :  Amoeba,  Paramoecium, Plasmodium.Phylum : Porifera .These are multicellular, aquatic organisms. They have cellular grade of construction without the occurrence of tissues. The sponges belonging to this  phylum  are  characterised  by  the  presence  of  a  canal  system  in  their body. The body wall contains spicules. They can reproduce both by asexual and sexual methods. Ex : Sponges. Phylum : Coelenterata or Cnidaria All coelenterates are aquatic animals. They are mostly marine. The body is radially symmetrical. The body wall is of two layers of cells. The outer layer  is  called  the   ectoderm.  The  inner  layer,  entoderm  is  seperated  fromthe ectoderm by a non-cellular mesogloea. The mesogloea is a jelly-like sub-stance. Due to the presence of two layers in the body wall, these are said to be diploblastic  animals. Many coelenterates exhibit  polymorphism . In this phylum, organisms exist  in  two  different  body  forms  namely,  a  polyp,  and  a  medusa. The ectoderm  contains  stinging  cells  called  nematocysts ( Cnidoblasts ).  These cells when triggered can explosively penetrate prey and inject poison. The layers in the body wall contain several cells and tissues such as muscle cells epithelial tissues, gland-cells and sensory cells. The layers in the body wall contain several cells and tissues such as muscle cells epithelial tissues, gland-cells and sensory cells. They  reproduce  both  asexually  and  sexually.  They  are  divided  into three classes, namely Hydrozoa, Scyphozoa and Anthozoa. In  Hydrozoa,the animal has a dominant polyp body form and a reduced medusa stage. (e.g) Hydra,  Obelia. The layers in the body wall contain several cells and tissues such as muscle cells epithelial tissues, gland-cells and sensory cells. They  reproduce  both  asexually  and  sexually.  They  are  divided  into three classes, namely Hydrozoa, Scyphozoa and Anthozoa. In Hydrozoa, the animal has a dominant polyp body form and a reduced medusa stage. (e.g) Hydra,  Obelia. In Scyphozoa the medusa form is permanent. This group includes jelly fishes  such  as  Aurelia.  They  swim  in  the  surface  waters.  They  have  a  bell shaped  medusa  stage. The  Anthozoans  mostly  remain  as  polyps.  Their  body  cavity  is divided     by     large     radial     partitions     called     mesenteries.(eg)     sea-anemone  and  corals.All  animals  of  subsequent  phyla  show  the  following  general characters.

Planaria Tape worm Liver fluke

1.  All  of  them  have  three  layers  in  the  body  wall.  They  are  named as  outer  ectoderm,  middle  mesoderm,  and  inner endoderm.  Thus  they  are called  as  Triploblastic animals.

2.  The  body  is  bilaterally  symmetrical.