BIOL 1604 Lecture Notes - Lecture 7: Osmoregulation, Manowar, Obelia
Document Summary
Radial or bilateral symmetry around a longitudinal axis. Diploblastic: epidermis and gastrodermis derived from embryonic ectoderm and endoderm respectively. Mesoglea (extracellular matrix) between the two body layers. 8cytes present, some housing nematocysts (stinging organelles) Asexual reproduction by budding in polyps forms clones and colonies. Fission and laceration are also present: when buds stay attached to the polyp that made them, a colony forms (common gastrovascular cavity) polyps (zooids) can specialize. Sexual reproduction by gametes in all medusa and some polyps. Asexual and sedentary - sessile: medusa. Alternate generations: life cycle involves both polyp and medusa stages. Most carnivores, effective predators: use tentacles and nematocysts in cnidocytes to capture prey, gastrovascular cavity acts as stomach. Tentacles: capture prey, usually encircle mouth or oral region. Nerve cells: base of epidermis, base of gastrodermis. Cell organs include statocysts (for balance) and ocelli (photosensitive organs).
