Parazoa

A lack of true tissues

Porifera

Unicellular Choanoflagellates - Tiny, single-celled protists with a characteristic collar and flagellum that usually live in colonies. Some sponge cells are almost identical to choanoflagellates.

About 15000

In the Precambrian era - around 700 mya

A hole in the body wall of the sponge made from a porocyte. It allows water flow into the spongoceal from the outside environment and filters food out.

The outer layer of cells that is contacting the environment and consists of a single layer of pinacocytes that may be modified to form porocytes.

Gelatineous matrix between inner and outer layers that contains Amoebacytes.

Nutrient transport, gamete formation, secrete the skeleton.

Spongin (collagen-like protein) Spicules (made from calcium carbonate or silica) or spicules embedded in spongin.

Inner layer that lines the spongocoel and consists of a single layer of choanocytes

In some species they form gametes, but their main function is feeding.

They have a flagellum which beats to create the flow of water and a mucous-coated collar which traps food particles.

The Choanocyte's collar traps food which is taken up into vaculoes and digested using enzymes. It is then passed onto amoebacytes which distribute nutrients to other cells in the mesohyl and pinacoderm.

Calcarea (400 spp. calcium carbonate spicules, tend to be small and tubular or vase-shaped) Demospongiae (95% of spp, very diverse, spongin and silicaceous spicules, include "bath sponges") and Hexactinellida (nearly all deep-sea spp, mostly vase- and funnel-shaped ranging from 7.5cm-1.3m)