Phylum Porifera
(Pore bearers)

These are multicellular, non-motile aquatic organisms, commonly called as sponges. Body is perforated with many pores called ostia. Water enters into the body through ostia and leads to a canal system. It circulates water throughout the body and carries food, oxygen. The body wall contains spicules, which form the skeletal framework. Reproduction is by both asexual and sexual methods. e.g- Euplectella, Sycon.

Phylum Coelenterata

Coelenterates are aquatic organisms, mostly marine and few fresh water forms. They are multicellular, radially symmetrical animals with two layers. The tentacles bear stinging cells called cnidoblast or nematocyst. They reproduce both asexually and sexually. e.g. Hydra, Jellyfish.

Phylum Platyhelminthes
(Flat worms)

They are bilaterally symmetrical, triploblastic, acoelomate (without body cavity) animals. Most of them are parasitic in nature. Suckers and hooks help the animal to attach itself to the body of the host. Excretion occurs by specialized cells called flame cells. e.g- Liverfluke, Tapeworm.

Phylum Aschelminthes
(Round worms)

Aschelminthes are bilaterally symmetrical, triploblastic animals. The body cavity is a pseudocoelom. They exist as free-living soil forms or as parasites. The body is round and pointed at both the ends. It is unsegmented and covered by thin cuticle. e.g. Ascaris, Wuchereria.

Phylum Annelida
(Segmented worms)

These are bilaterally symmetrical, triploblastic, first true coelomate animals with organ-system grade of organization. Body is extremely divided into segments called metameres joined by ring like structures called annuli. e.g. Earthworm, Leech.

Phylum Arthropoda
(Animals with jointed legs)

They are bilaterally symmetrical, triploblastic and coelomate animals. They can be found in all types of habitats–land, water and soil. They have jointed limbs. The body is segmented into three regions–Head, Thorax and Abdomen. e.g. Prawn, Crab.

Phylum Hemichordata

Hemichordata is bilaterally symmetrical, triploblastic and coelomate animals. They are exclusively marine animals. They can be solitary or in colonies. Hemichordata have a true body cavity or coelom. e.g. Balanoglossus (Acorn worms).

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