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Phylum - Mollusca

These are soft-bodied animals that are bilaterally symmetrical and triploblastic.

They are mostly aquatic and few terrestrial forms. Their soft body is covered by a exoskeleton which is made up of calcareous shell.

Between the exoskeleton and the visceral mass there is a membrane called mantle which posses a cavity called mantle cavity.

Sexes are usually separate except a few which are hermaphrodite. Eg. Pila, Chaetoderma, Aplysia etc.





Phylum - Arthropoda

These are metamerically segmented animals that possess jointed appendages.

Their body is covered by thick chitinous exoskeleton, which moults periodically.

The body cavity is haemocoel with open type of circulatory system.

Sexes are generally separate and sexual dimorphism is often exhibited. Fertilization is internal with larval stages.

Eg. Limulus (king crab) Periplanata americana (cockroach) etc.

Periplanata americana (Cockroach)



Phylum - Echinodermata

These are animals, which exhibit radial symmetry and possess peculiar water vascular system.

They are usually triploblastic, coelomate animals with oral and aboral surface.

They possess special structures called tube feet used for locomotion and water vascular system.

Sexes are usually separate. Sexual reproduction is common except a few which reproduce by regeneration.

Eg: Asterias, Ophiothrix, Echinus etc.


This phylum is further divided into sub phylum
  1. Hemichordata eg. Balanoglossus.
  2. Urochordata eg. Ascidia.
  3. Cephalochordata eg. Amphioxus.
  4. Vertebrata eg. All vertebrates are animals with back-bones.
Sub-phylum vertebrate is further divided into classes.
  1. Pisces eg. Scoliodon (shark)
  2. Amphibia eg. Bufo (toad).
  3. Reptilia eg. Naja (cobra).
  4. Aves eg. Columba (Pigeon).
  5. Mammalia eg. Homosapiens (Man).

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