Invertebrate Phyla

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Cnidaria (Coelenterata)

Mostly aquatic, marine

Solitary or colonial

sessile or free-swimming

radially symmetrical

possess 'stinging cells' called cnidoblasts or cnidocytes

Cnidocytes/blasts used for anchorage, defence, and capture of prey

1st to exhibit 'Tissue level of organisation'

Diploblastic

Posses Gastro-vascular cavity or Coelenteron

Cavity serves for both digestive and circulatory functions

Digestion is both Extracellular ( in the coelenteron) and Intracellular ( in nutritive muscular cells)

Nervous system forms diffuse nerve net

Sensory structures such as statocyts occur in medusiod forms

Coral formingn cnidarians have calcium carbonate exoskeleton

Shows 2 basic body forms : 1. Polyp -Cylindrical

2.Medusa -umbrella

Some exist in both forms exhibit Metagenesis

medusae forms polypoid sexually and polypoid gives medusae asexually

Asexual reproduction includes budding

Sexual reproduction by syngamy

Indirect development

Free swimming ciliated larva - Planula

Eg:- Physalia

Adamsia

Pennatula

Rhizostoma

Meandaria

Include 3 classes

* Hydrozoa

* Scyphozoa

*Anthozoa or Actinozoa

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CTENOPHORA

Commonly called ' Sea Walnuts' or 'Comb Jellies' or 'Sea Goseberries'

Exclusively marine

Radially symmetrical

Diploblastic

Tissue level of organisation

Body bears 8 external rows of ciliated comb plates

Comb plates help in locomotion

Cnidocytes are absent

Have glue cells called 'Lasso cells' or 'colloblasts'

glue cells help in food capture

digestion both extra and intra cellular

Has Bioluminescence

Reproduction only by sexual method

Sexes are not separate

Fertilization is external

indirect development

Larval stage called Cydippid larva

Eg:- Pleurobrachia

Hormiphora