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CBSE Class 11th Biology Notes for Chapter 4 Animal Kingdom

   Chapter 4 Animal Kingdom
1. Levels of organization: Classified according to the pattern of the organization of cells.
2. Symmetry: Classified on the basis of the symmetry of their bodies.
3. Diploblastic and Triploblastic organization: Animals in which the cells are arranged in two embryonic layers, are called diploblastic. Those animals in which the developing embryo has an additional third germinal layer, are called triploblastic animals.
4. Coelom: Classification is done on the basis of the presence or absence of a cavity between the body wall and the gut wall called coelom.
5. Segmentation: In some animals, the body is externally or internally divided into segments with a serial repetition of at least some organs.
6. Notochord: Classification is done on the basis of the presence or absence of the notochord which is a mesodermally derived rod-like structure formed on the dorsal side during embryonic development in some animals.

  1. Phylum- Porifera
  2. Members commonly known as sponges
  3. Generally marine and mostly asymmetrical animals
  4. Primitive multicellular animals having a cellular level of organization.


  1. Phylum- Coelenterata
  2. Aquatic, mostly marine, free swimming animals
  3. Have radial symmetry
  4. Have tissue level of organization and are diploblastic.


  1. Phylum- Ctenophora
  2. Commonly known as sea walnuts.
  3. Marine, radially symmetrical
  4. Diploblastic organisms with tissue level of organization


  1. Phylum- Platyhelminthes
  2. Have dorso-ventrally flattened body and are called flatworms.
  3. Bilaterally symmetrical, tiploblastic with organ level of organization.
  4. These are mostly endoparasites found in animals including human beings.


  1. Phylum- Aschelminthes
  2. Circular cross-section
  3. Organ level of organization, bilateral symmetry, triploblastic


  1. Phylum- Annelida
  2. Organ system level of organization, bilateral symmetry


  1. Phylum- Anthropoda
  2. Phylum- Mollusca
  3. Phylum- Echinodermata
  4. Phylum- Hemichordata
  5. Phylum- Chordata

The subphylum Vertebrata is further divided as follows:

  1. Class- Cyclostomata
  2. Class- Chondrichthyes
  3. Class- Osteichthyes
  4. Class- Amphibia
  5. Class- Reptilia
  6. Class- Aves
  7. Class- Mammalia

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