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Phylum Mollusca (Mollusk)- soft A. Introductory facts 1. third largest in the animal kingdom, estimates of 100,000 species 2. Extreme diversity in form (from slugs and snails to oysters and clams to squid and octopi) and habitats (terrestrial, marine, and fresh water) 3. Large range in size (includes the largest invertebrate (giant squid), weighing up to 4,000 lbs. and 60 feet long all the way down to 0.5 inch long slugs B. Characteristics of entire phylum 1. ________blastic 2. __________ digestive system 3. ____________ (body cavity w/ membranes) 4. ____________symmetry B. Characteristics of entire phylum 5. Two part body connected head/foot (head contains senses and mouth /foot for locomotion) visceral mass (section with digestive, respiratory, circulatory, reproductive organs) B. Characteristics of entire phylum 6. Mantle tissue a. often connected to the visceral mass and encircling much of the body b. often secretes a shell of calcium carbonate 7. Radula – inside the mouth are rows of rasping “teeth” on a “tongue” that scrape the food back to the esophagus 8. An idealized mollusk would crawl on a single flat, muscular foot, and the body would have a head at one end and an anus at the other. Above the body would be an external shell mounted on a visceral hump containing internal organs. Class Polyplacophora Chiton – ancestor dorsal shell which is composed of eight separate shell plates hinged with one another which permit the chiton to bend and also the animal can slowly curl up into a ball C. Class Gastropoda 1. 2. (gut – foot) 35,000 species (largest class & most varied) Ex. snail conch Cone shells Sea slug Welk 3. Torsion – 180` counterclockwise twisting of the internal visceral organs Advantage of torsion Head is withdrawn into mantle cavity first, then foot (operculum serves as a lid) Clean water is drawn into mantle from front, rather than stirred up water from back Better sensitivity (chemosensory) Disadvantage Anus is positioned directly above head Some species will detorsion 90 so anus is on side 5. Locomotion – use cilia on mucus trail if small, muscular waves if larger 6. Feeding – a. herbivores scrape algae or eat land plants with their radula - Food is trapped in ‘strings’ of mucus called protostyle b. a few are predators on other mollusks, starfish, jellyfish, sponges, and coral 7. Respiration siphon – inhalant tube to lungs on land, to gills for marine 8. Circulatory - open system w/ heart - blood used to give pressure support 9. Hydrostatic skeleton 10. Reproduction dioecious – marine monoecious - land "Giant African land snail" introduced (non-indigenous species) considered a serious agricultural pest in the United States. reach up to 8 inches in length and 4 inches in diameter. about the size of an average-size adult fist. have a voracious appetite known to eat at least 500 different types of plants, including peanuts, beans, peas, cucumbers, melons, a wide variety of ornamental plants, tree bark, and even paint and stucco on houses. Snails contain both male and female reproductive organs, and can lay up to 1,200 eggs per year. C. Class Bivalvia (two leaves) also know as Pelicypoda (hatchet – foot) 1. 2. 30,000 species Ex. oyster clam scallop mussel 3. Special traits a. Muscular foot is elongated and narrow (hatchet); used to dig into the sand to move and to partially bury the animal b. Shell has two halves (valves) • Secreted by mantle • Calcium carbonate • Hinged • Opened and closed with a pair of adductor muscles • Growth increases from the umbro (oldest portion) 4. feeding • filter feeders •oysters and clams eat plankton. •by pumping water through their bodies the mollusks strain the microscopic organisms through their gills which act as sieves. Bivalve dissection Part 2 Part 3 5. oddities a. Some scallops have multiple eyes b. biggest bivalve mollusk is the clam Tridacna • native to the IndoPacific • reaches a weight of 500 pounds. c. How do you make a cultured pearl ? The inside of an oyster's shell is covered with a smooth shiny coating called nacre, or mother-of-pearl. an irritant gets caught inside the oyster's shell and it secretes layers of nacre to protect its body by coating it: this is the pearl. Man can force the oyster to produce a pearl by inserting an irritant purposefully into the shell. It takes the oyster two to three years to produce a good size pearl. Cultured pearls are usually not perfect, but the Japanese have discovered that if you surgically insert an irritant directly into the body of the oyster this will produce a perfect pearl. The largest pearl ever found is reported to be four inches around and two inches long. 6. reproduction Dioecious Marine - external fertilization Freshwater – internal Sperm brought in w/ water Larvae mature in the gill area and then parasitize fish for two to three months by clamping on to their gills or fins with their valves, then release. Enables individuals to travel far from their parents. 7. Zebra mussel Non-indigenous (not native) to U.S. 1985 was accidentally brought to Great Lakes in the tanks of cargo ships from Europe Clog water intake pipes to power plants and drinking water supplies D. Class Cephalopoda (head foot) 10,000 species 2. ex: 1. Chambered nautilus squid Cuttle fish 3. characteristics Anterior portion of foot modified into circle of tentacles or arms Posterior foot has become a funnelshaped siphon Mantle/siphon used for propulsion Mantle relaxes, the mantle cavity fills with water, contraction of mantle forces water out siphon When threatened can secrete a dark ink so that it swim away concealed Webbed octopus Reduced shell or no shell (octopus) Nautilus are only remaining cephalopod w/ external shell Squid –internal structure (pen) Cuttlefish – cuttlebone (used for pet birds) Webbed octopus octopus Cephalopods are predators that use tentacles with suction discs to capture their prey. A radula moves the prey to the beaklike jaws of the mouth that bite and crush it. Some cephalopods also secrete venom into the prey. attack color changes mimic octopus How intelligent are they? Cuttlefish: Kings of Camouflage Dissection walk-through 4. giant squid Gigantic carnivorous squid a beak-like mouth powerful enough to cut through steel cable. Eyes are the largest in the animal kingdom, getting to be as big as a basketball (18 inches across). nearly 60 feet long, largest invertebrate on Earth. suckers help the squid capture its prey and defend itself against attackers such as the sperm whale. Witnessed? 4. giant squid Giant squids are hunted by the sperm whale. Many have been seen in battle, and beaks and tentacles have been found inside sperm whale's stomachs. There is at least one eye-witness report of a smaller whale being drowned by the giant squid. Kraken are legendary sea monsters of gargantuan size, said to have dwelt off the coasts of Norway and Iceland. 5. Chambered nautilus •Have a unique shell that closes off the smaller portions as it grows (chambered) •Closed off chambers are filed with air to help the nautilus stay bouyant Nautilus eating a crab