BIOL 1202 Chapter : Ch 33
Document Summary
Concept 33. 1: sponges are basal animals that lack true tissues. Porifera: phyla calcarea and silicea: live in both fresh and marine waters, lack true tissues and organs, asymmetrical body. Sponges are suspension feeders: filter water passing through their bodies, figure 33. 4. Concept 33. 2: cnidarians are an ancient phylum of eumetazoans. A wide range of sessile and floating forms including jellyfish, corals, and hydras. Simple diploblastic, radial body plan: body plan is a sac with a central gastrovascular cavity, single opening serves as both mouth and anus, mesoglea layer between epidermis and endodermis (gastrodermis). Medusa form moves freely in water by passive drifting and contractions of the bell. Cnidocytes: unique cells that function in defense and the capture of prey. Stimulus causes the cell to evert releasing thread. Concept 33. 3: lophotrochozoans, a clade identified by molecular data, have the widest range of animal body forms: figure 33. 2, bilateria show cephalization and 3 tissue layers.
