Give general characteristic of phylum Porifera. 

Explanation

Phylum Porifera (Porous - Pore ferre - to bear) includes the first and most primitive group of multicellular animals referred to as porifcrans, in porc bcaring animals.
They are primitive, multicellular animals and are commonly called sponges,
They are generally marine and mostly asymmetrical animals.
These are primitive multicellular animals and have cellular level of organisation.
Sponges have a water transport or canal system.
Water enters through minute pores (ostia) in the body wall into a central cavity, spongocoel from where it goes out through the osculum.

This pathway of water transport is helpful in food gathering, respiratory exchange and removal of waste.
Choanocytes or collar cells line the spongocoel and the canals.
Digestion is intracellular.
The body is supported by a skeleton made up of spicules or spongin fibres.
Sexes are not separate (hermaphrodite), i.e., eggs and sperms are produced by the same individual.
Sponges reproduce asexually by fragmentation and sexually by formation of gametes.
Fertilisation is internal and development is indirect having a larval stage which is morphologically distinct from the adult.
Development is mostly indirect with larval stages called parenchymula (leucosolenia) or amphiblastula (Sycon).
Examples : Sycon (Scypha), Spongilla (Fresh water sponge), Euspongia (Bath sponge).