Phylum Porifera
Characteristics
The simplest of all animals with no formal digestive, circulatory, or nervous systems. They display radial symmetry and assymmetry. They have two layers: an endoderm and an ectoderm. Most are salt water sponges.
Classification
The four classes are grouped according to skeletal structure.
Protection
Some members are poisonous or they taste bad.
Movement
Adults are sessile (they don't move) while larvae are free swimming.
Feeding & Digestion
Porifera are filter feeders (they filter food out of the water). They have intracellular digestion.
Circulation
Circulation in porifera is mainly carried out through diffusion.
Reproduction
Reproduction can be asexual or sexual. Asexual forms include fragmentation, budding, and gemmules (amoebocytic sporulation). Since most sponges are hermaphroditic, sexual reproduction is carried out by releasing sperm into the current. Fertilization is internal and occurs when sponges filter the sperm from the current.
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