Phylum Porifera
Fig: Phylum Porifera = Pore Bearing
Important Characteristics:
- Phylum Porifera = Pore-bearing animals.
- Sponges are primitive multicellular animals with a cellular grade of organization.
- They have no fixed body shape & no plane of symmetry.
- Whole sponges can be regenerated from a few separated cells.
- Sponges are free-living aquatic (mostly marine) & having neither nerves nor muscles.
- Body wall with two layers of loosely arranged cells and mesenchyme in between (diploblastic).
- Reproduction occurs by asexual (external & internal buds) or sexual methods.
- The body-wall encloses a large cavity, the spongocoel & in most cases also contain numerous small canals.
- The ceaseless beating of flagella maintains s steady current of water through the canals to bring in food & oxygen & remove waters.
- Almost all sponges possess an internal skeleton. It may consist of tiny siliceous spicules or of fine spongin fibers or of both.
- Example: Sycon (Scypha), Spongilla (Freshwater sponge), Euspongia (Bath sponge)
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