Phyla Characteristics

Porifera (sponges)

no tissue layer, just colony of cells; asymmetrical; have spicules or spongin for support

Arthropoda (arthropods)

jointed appendages and segmentation

Platyhelminthyes (flatworms)

first to have bilateral symmetry and have three tissue layers; have gastrovascular cavity (incomplete) or lack digestive system

Nematoda (roundworms)

first to have complete digestive system; major decomposer and some parasitic

Annelida (segmented worms)

first to have segmentation; have closed circulatory system

Rotifera (rotifers)

have circular wheels of cilia that whirl funneling food into their mouths

Cnidaria (cnidarians)

have stinging cells on tentacles and two tissue layers; two body plans called medusa and polyp; radial symmetry

Mollusca (mollusks)

muscular foot, mantle and often a radula

Chordata (chordates)

only a few are invertebrates; almost all are vertebrates; have notochord, hollow dorsal nerve cord, pharyngeal gill slits, and postanal tail sometime during life

Echinodermata (echinoderms)

spiny skin and water vascular system