BIOL 1010 Lecture Notes - Lecture 44: Gastrovascular Cavity, Hydrostatic Skeleton, Sea Anemone
Document Summary
Contractile tissues & nerves occur in simplest forms in. Hydras (found in freshwater/lake) & sea anemones have cylindrical body with tentacles projecting from one end: mostly sedentary. Mouth on top of the body at the hub of radiating tentacles. Marine jelly (jelly fish) ----------------------------------------------------: move freely in h20. Shape: umbrella with fringe tentacles around lower edge. Some pass through both polyp & medusa life cycles. Cnidarians are carnivores that use tentacles to capture small animals/protists & push prey into mouths. Gastrovascular cavity. (gaster belly, vas vessel) where food is digested. Mouth is the only opening in the body; it is also the exit for undigested food/wastes: fluid in the gastrovascular cavity circulates/transports nutrients, oxygen, & h20 to internal cells & removes metabolic wastes. Fluid also acts as hydrostatic skeleton, supporting & helping body to give cnidarian shape. (h20 giving shape to balloon: when animal closes mouth, the volume of the cavity is fixed.