Kingdom: Animalia Phylum:Mollusca Classes: Bivalva, Gastropoda, Cephalopoda http://www.youtube.com/watch?v=0a7j5prl8hc&feature=related http://www2.beavercreek.k12.oh.us/videos/45/pgr45_700k.asf What is a Mollusk? Can live in ocean, freshwater, or moist land Bilateral symmetry, coelom, two body openings, a muscular foot, and a MANTLE MANTLE thin membrane that surrounds the internal organs. May secrete a shell RADULA located within the mouth, some mollusks use this structure as a scraping organ with rows of teeth Class: Gastropoda Snails, conches, limpets, slugs, sea slugs or nudibranchs May have one shell or no shell If no shell, it is protected by a thick mucus that is sometimes toxic Name means Stomach foot Uses foot to move All have a radula, open circulatory system, gills, and nephridia NEPHRIDIA primitive kidneys Cool fact: Nudibranchs eat jellyfish and can use the jellyfish nematocysts as their own weapons. It will sting any fish trying to eat it. Have you ever watched a snail eat? May 7 11:14 AM 1
Class: Bivalva Clams, muscles, oysters, & scallops. Live in fresh or salt water. Two shelled mollusks belong to the class Bivalvia. These are Pelcypods meaning axe or hatchet foot. It uses its foot to pull itself through the sand or mud and bury itself. Bivalves are filter feeders. They have cilia which beat to create a water current flow through the incurrent siphon. As water flows over the gills, food and sediment become trapped in the mucus. Cilia push food to the stomach and sort out the sediment toward the mantle and out the excurrent siphon. May 17 10:20 AM 2
Cephalopods: Head footed mollusks belong to the class Cephalopoda. Examples: Octopus, Squid, cuttlefish and chambered nautilus. These animals are the most complex of the mollusks. The foot has developed into tentacles, suckers, hooks, or adhesive structures. Tentacles capture prey and bring it to their beaklike jaws. They move water forcefully through their siphons and move by jet propulsion. They also can release a dark fluid ink like a cloud to help confuse predators. May 7 11:18 AM 3
A. Reproduction in Mollusks Most mollusks have separate sexes and reproduce sexually. Sperm and eggs are released into the water at the same time and fertilization is external. Snails and Slugs are hermaphrodites because they move slowly and it increases the likelihood of fertilization Larval stages of mollusks are similar See Fig. 27.4. Some aquatic species have free swimming larvae. Marine snails and bivalves have a developmental stage called a veliger that have the beginnings of a foot, shell, and mantle. Nudibranch egg mass Squid mating Conch egg case May 7 11:19 AM 4
Compare and Contrast the three classes of Mollusks Gastropods Cephalopods Bivalves May 8 10:46 AM 5
SEGMENTED WORMS Kingdom: Animalia Phylum: Annelida Classes: Oligochaeta, Polychaeta, Hirudinea A. Examples: Earthworms, Bristle worms, & Leeches 12,000 species. B. Bilaterally symmetrical, have a coelom and two body openings(mouth & anus). C. The Body plan has a tube within a tube arrangement. D. Setae = Bristles found in most segmented worms that anchor their bodies in order for the worm to move itself along. E. Segmentation supports diversified functions. F. Nerve cords connect the brain to nerve centers called ganglia. G. Circulation and respiration = have a closed circulatory system and their skin must be in water or moist soil as CO2 is exchanged for O2 through the skin. H. Reproduction in segmented worms 1. All are hermaphrodites. Earthworms are not self fertilizers even though they are hermaphrodites. 2. They exchange sperm form a capsule around themselves. Deposit eggs & sperm in the capsule. Earthworms leave the capsule in the soil and the young worms eat the capsule until they are large enough to extract food from the soil. May 7 11:20 AM 6
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Polychaeta Pompeii Worm Hirudinea Leech May 12 12:48 PM 9
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1. Clitellum 2.Genital setae 3.Sperm Grooves 4.Sperm Ducts 5. May 12 12:43 PM 12
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