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Lower Invertebrates Dr. Christine Palmier Biology 120 Lab Lower Invertebrates Lower Invertebrates Animals • • • • • • Invertebrates Vertebrates (More abundant) (Less Abundant) Evolution and Development of Bilateral symmetry Appearance of a head (cephalization) Digestive system True coelum (body cavity) Segmentation Lower Invertebrates Sponges (Porifera) P. Porifera = sponges most primitive did not give rise to other animals asymmetrical, some radial symmetry sessile (immobile) adults, free-swimming larvae 2 cell layers • 1) outer = epidermal • 2) inner = flagellated collar cells ˜ (bring water and food inside thru osculum filter-feeding) skeleton composed of spicules (Calcium carbonate and spongin) and secreted by amoeba-like cells Lower Invertebrates Sponges (Porifera) Lower Invertebrates P. Cnidaria P. Cnidaria = corals, hydra, sea anemones, jelly fish radial symmetry (advancement vs. some sponges) 2 body forms • a) sedentary polyp (hydra) • b) motile medusa (jelly fish) Sac-like gut, one opening (no anus) 2 cell layers • a) epidermis • b) gastrodermis, jelly to separate layers and allow buoyancy for floating of medusa Stinging nematocysts to capture prey/food and defense Lower Invertebrates Hydra ,Jelly Fish, Sea anemones Coral, (Cnidaria) Lower Invertebrates Hydra ,Jelly Fish, Sea anemones Coral, (Cnidaria) Lower Invertebrates 1) Hydrozoans—marine and colonial Polyp is predominant (sessile, immobile) Use polyps for feeding, sting prey and for reproduction 2) Jellyfish “true” polyp form is reduced or absent horse-shoe shaped gonads 3) Corals and sea anemones Only polyp form is present Stinging tentacles to capture drifting food secrete calcium carbonate coral reefs Sea anemones do not have calcium carbonate contain symbiotic algae Lower Invertebrates Jelly fish medus and polyp Lower Invertebrates Coral and Sea Anemone Lower Invertebrates P. Platyhelminthes P. Platyhelminthes –“flat worms” Still only one opening for digestive system (no anus) Advances include • 1) more specialized tisses • 2) several, well-developed organ systems • 3) bilateral symmetry (first time) head development/cephalization localization of sense organs Lower Invertebrates P. Platyhelminthes –“flat worms” Lower Invertebrates Free Living Parasitic Planaria—feed on small animals or scavenge (dead, organic matter) • cilia for movement flukes—parasitic; in liver, lungs, bladder, or blood vessels of vertebrates • • • • suckers for attachment to host monoecious/hermaphroditic or dioecious primary host for adult fluke = vertebrate intermediate host for larvae = usually a snail tapeworms—specialized parasites for life in intestine (pre-digested food) • attach to host by scolex (suckers & hooks) • proglottids follow scolex ˜ ˜ formed by budding, reproductive unit (1000s/1 proglottid) leave host thru feces new hosts (muscle of cattle & pigs) poorly cooked human intestine Lower Invertebrates Planaria Lower Invertebrates Flukes Lower Invertebrates tapeworm Lower Invertebrates P. Nematoda P. Nematoda • Most widespread of organisms • complete digestive system (mouth and anus) • False body cavity present (filled w/ reproductive organs)—no protective lining around organs, but some separation of organs • Some parasites of plants and animals Lower Invertebrates Nematodes (round worms) Ascaris Lower Invertebrates Vinegar eel Lower Invertebrates Trichnia Lower Invertebrates Today’s Lab Look at: • Models and diagrams of sponges • prepared slide of spicules • bath sponge vs. basket sponge • specimens of Cnidaria and identify radial symmetry, tentacles, mouth, sac-like cut, polyp, medusa • Portuguese man-of-war (Cnidaria, hydrozoan)—specimens and pictures • Obelia (Cnidaria, hydrozoan)—life cycle, demo slides of colony and medusa • For hydrozoa, draw reproductive polyp, feeding polyp, and medusa • Moon jelly—life cycle, tentacles, medusa, 4 oral arms, gonads • Coral—development of coral reefs, specimens, pictures • Sea anemones—pictures and preserved specimen • hydra—feed them, cause discharge of nematocysts, slide or picture of nematocyst, model Lower Invertebrates
