1. Classification of Animals
The structural organization -1]Protozoa 2] Metazoa
Body symmetry -1]Asymmetrical 2]symmetrical
The symmetrical animals may have any one of the following symmetry 1 Bilateral symmetry as in frog ,rat etc. 2 Radial symmetry as in hydra,starfish etc 3. Spherical symmetry as in some sea-urchins.
3.Presence or absence of Notochord
4.Presence or absence of coelom or body cavity
5. Organs of locomotion
Considering the above characteristics the sub-kingdom “metazoa” is classified into ten phyla.

2. Coelenterata
All are aquatic,mostly marine.
The simple body of these animals consist of two layers of cells outer inner.with radial symmetry.
They have a body cavity .
Body has a single opening at Hypostome surrounded by sensory “tentacles”
These animals reproduce asexually by “budding”
e.g.hydra,jelly fish

3. Mollusca
These animals mostly aquatic with unsegmented soft body covered in a shell, bilater Characteristicsally symmetrical or a symmetrical as in pila
The body is distinguished into three parts.
Anterior head with sense organs.
Dorsal visceral mass with organ system.
Ventral foot for locomotion
Eg snails,octopus,etc

4. Arthropoda
These are triploblastic, cylindrical,segmented,burrowing worms having a bilateral symmetry.
They have a true coelom with simple organ systems.
Few of them are parasites [Leech-ecoparasite]
Locomotion occurs by setae
They are found in marine water,fresh wateror on land
Eg 1Leech 2 nereis 3 Earthworm

5. Echinodermata
These are mostly marine, unisexual, triploblastic animals having a tough spiny exoskeleton made up of calcium.
Their body is unsegmented and hard with aradial symmetry.
They have a developed coelom and derive their food from water vascular system.
Have tube feet for locomotion They have “Regeneration “ capacity.
Eg. star fish,sea-cucumber etc.