Chapter 34-35 Guided Notes 34.1 Phylum Platyhelminthes Flatworms Invertebrates w/ soft, symmetry 3 tissue layers organized into organs & systems Exhibit Planaria Freshwater -shaped anterior and a posterior Planarian Digestion & Excretion feed on decaying or and smaller org s Food is ingested thru the Planarian Neural Control more complex than nerve net of cnidarians cerebral ganglia: serves as simple sense w/ eyespots Planarian Reproduction Hermaphrodites Sexual: eggs are laid in Asexual: body undergoes 2 halves missing parts Parasitic Fluke -shaped flatworms clings to host by anterior and ventral Simpler nervous system External surface is covered by protective layer = Fluke Reproduction & Life Cycle life cycles may involve more than one host Ex- blood flukes use as primary hosts and as intermediate hosts 1
Ex- Liver fluke requires a and a Enters human because unsanitary conditions Tapeworms can live in the of almost all vertebrates surrounded by tegument Attaches to the host w/ scolex ( and ) Tapeworm Structure NO light-sensing organs, mouth, gastrovascular cavity, or digestive organs Produces new behind head (may exceed 10 m long) Each segment has both & organs o eggs are fertilized in segment o segment breaks off & leaves host s body Ex- beef tapeworm primary host is human and intermediate host is cow larvae form (dormant larvae) in muscle tissue of the cow 34.2 Phylum Nematoda roundworms phylum of worms slender, at both ends 2 body openings ( & ) covered by a protective cuticle Most species are ; some separate sexes Types of Roundworms A) Ascaris infects,, and eggs enter hosts thru contaminated food or water o masses of worms can block intestines & cause Prevention = B) Hookworms intestinal parasites that feed on blood o Produce larvae in o larvae enter hosts thru 2
o infect ~1 billion people Prevention = C) Trichinella infects humans, other mammals infected from pork may be infested w/ (young worm w/ protective covering) causes the disease trichinosis Prevention = Other Parasitic Roundworms Pinworms- common human parasites do not cause serious diseases Filarial worms- infects people in countries infect and may cause elephantiasis Ex- Heartworms may live in and block valves Prevention: 35.1 Phylum Mollusca clams, snails, slugs, squids, octopuses symmetric invertebrates Some have a Most aquatic mollusks and annelids have a larval stage = Mollusk Body Plan visceral mass: contains body organs head-foot: Head-, structures Foot- large, muscular organ for Mantle: layer of epidermis that covers secretes the or protects the body if lacking a shell Mantle cavity: houses the nervous system consists of paired clusters of nerve cells = ganglia Use radula ( -like organ w/ rows of teeth) to scrape food off of rocks Class Gastropoda Largest and most diverse class of gastropods 3
1 shell ( ) = snails, abalones, whelks, conchs No shell = slugs, nudibranchs Snails Have circulatory system in which heart pumps hemolymph ( ) from gills or lungs into the hemocoel (body cavity) moist and aquatic environments at end of Survive dry periods by retreating into shells and sealing opening w/ plug Other Gastropods Slugs- terrestrial Nudibranchs- marine Pteropods ( )- have foot that is modified into a winglike flap, used for swimming gastropods use muscular contractions of to move on mucus trail (Snails, slugs) Protected by mucus layer & are eaten by humans Class Bivalvia Bivalves: shell divided into valves connected by clams, oysters, mussels, scallops sessile lack distinct head 3 pairs of Mantle secretes shell in layers layer = mother of pearl middle layer provides Outer layer is drawn across by for respiration Clams Burrow into mud and sand w/ their move thru a pair of hollow, fleshy tubes = siphons Water enters thru siphon Water leaves thru siphon 4
Other Bivalves & - attach to hard surface Scallops- move by quickly and their shells Class Cephalopoda Cephalopods = - octopuses, squids, cuttlefishes, chambered nautiluses Foot divided into w/ to catch prey beaklike jaws on head moving and extremely predators Many use to hide and disguise themselves Well developed nervous system w/ large circulatory system Squids tentacles move by (force H2O out siphon and move in direction) & steer w/ fins on mantle Octopuses tentacles, similar to squids along ocean bottom or and wait for prey Chambered Nautiluses Only existing cephalopod that has shell Shell is and into chambers body is chamber Uses of Mollusks Hermit crabs use empty shells for their Pearls are produced by covering a grain of w/ mother-of-pearl Scientists study their to see how learning and memory work Problems w/ Mollusks Damage (snails, slugs) Often contain that can infect humans 5
35.2 Phylum Annelida Annelids = symmetrical, worms earthworms, feather-duster worms, leeches have external (setae) and some have protrusions (parapodia) Class Oligochaeta body possesses more than segments Each segment has setae and parapodia and muscles Earthworm Feeding & Digestion ingest Soil is moved thru: a) e) gizzard: soil b) f) intestine c) esophagus g) d) crop: temporary Undigested soil & waste the soil Circulation Possess a & blood vessel Connect to pairs of (heart) circulatory system Respiration & Excretion and diffuse thru Wastes and excess water are excreted thru Neural Control chain of connected by ventral cord structures are found in all segments but are concentrated to end Reproduction During mating, earthworms together 6
held together by and secreted by clitellum Sperm moves to secretes a tube of mucus and chitin Fertilization occurs tube, forms a case for the young worms Class Polychaeta = setae in bundles Largest class of worms Some are Parapodia = and and specialized mouthparts only annelids to have stage retreat into tubes of CaCO3 and mucus when threatened Class Hirudinea smallest annelid class ~ species of leeches Many are but some are Leeches suckers suckers Saliva has an (host won t feel it) & an (blood won t clot) Can consume x its weight in blood Historical Use Doctors used to think sickness was caused by that could be sucked out by Medical Benefits Used in to keep blood flowing as doctors body parts 7