Theory:

Phylum: Annelida
Symmetry: Bilateral
Germ layer: Triploblastic
 
Earthworm.jpg
 
Characteristics:
  • Have defined organ system.
  • Segmented body called metameres.
  • Joints are ring-like annuli. Moist thin cuticle covers the body.
  • Moves with the help of setae and parapodia.
  • Hermaphrodites, having different sexes in the same body.
Example:
Nereis, Earthworm, Leech
Phylum: Arthropoda
Symmetry: Bilateral
Germ layer: Triploblastic
 
Scorpion.jpg
 
Characteristics:
  • Coelomate animals have defined organ structure like head, thorax and abdomen.
  • Arthropods have segmented body, and each segment has a pair of jointed legs.
  • The exoskeleton (outer skeleton) has chitin which is shed periodically when the animal grows. This process of shedding and growing of exoskeleton is termed as moulting.
  • The body cavity of these animals is filled with haemolymph. Haemolymph is like blood in a human being; however, the blood does not flow in these animals.
  • These animals possess gills or tracheae for respiration.
  • Green glands or Malpighian tubules help the animals to excrete.
  • Animals have separate sexes.
Example:
Prawn, Crab, Cockroach, Millipede, Centipedes, Spider, Scorpion
Phylum: Mollusca
Symmetry: Bilateral
Germ layer: Triploblastic
 
Octopus_macropus.jpg
 
Characteristics:
  • Have well-defined organ structure like head, muscular foot and visceral mass.
  • They do not have a segmented body.
  • Muscular foot help in movement.
  • Body is covered by a thick shell made up of calcium (Calcareous shell).
  • In some animals of this phylum, the blood is blue in colour. Giant pacific octopus has three hearts.
  • Octopus has a good sense of touch and taste!
  • The blue colour of the octopus blood is because of copper-rich protein in their blood called hemocyanin.
  • Respire with gills and lungs.
  • Exhibit larval stage of development.
  • Have separate sexes.
Example:
Garden snail, Octopus, Cuttlefish, Squid
Phylum: Echinodermata
Symmetry: Radial (Adult); Bilateral (Larvae)
Germ layer: Triploblastic
 
Starfish_02_(paulshaffner).jpg
  
Characteristics:
  • True coelomates with defined organ system.
  • They have a water vascular system - a fluid-filled body.
  • They have tube feet for movement.
  • They have spiny skin. The body is covered by calcareous spiny hard surface called calcareous ossicles.
Example:
Starfish, Sea urchin, Sea cucumber, Cystoidea
Phylum: Hemichordata
Symmetry: Bilateral
Germ layer: Triploblastic
 
hemichordata.png
 
Characteristics:
  • Coelomate animals found to have both non-chordate and chordate features.
  • They do not have a notochord.
  • They have gill slits.
  • These animals have cilia. Using cilia, they draw a current of water towards them. The cilia then filter out the microbes in the water as food.
Example:
Acorn worms (Balanoglossus)
Reference:
Free image credit:
Earthworm: https://upload.wikimedia.org/wikipedia/commons/6/6a/Earthworm.JPG
Leech: https://www.pikist.com/free-photo-vywpu
Scorpion: https://commons.wikimedia.org/wiki/File:Female_Emperor_Scorpion.jpg
Octopus: https://en.wikipedia.org/wiki/Aristotle%27s_biology#/media/File:Octopus_macropus.jpg
Starfish: https://commons.wikimedia.org/wiki/File:Starfish_02_(paulshaffner).jpg
Hemichordata: https://commons.wikimedia.org/wiki/File:Enteropneusta.png