Presentation on theme: "Mollusca Paul Ko Andy Zhao Michael Chiu Period 5"— Presentation transcript:
Mollusca Paul Ko Andy Zhao Michael Chiu Period 5
4 Major Classes: Polyplacophora Bivalvia Gastropoda Cephalopoda
Class Polyplacophora Chiton Marine Shell with Eight Plates Foot used for locomotion Radula No head
Bivalvia Clams and oysters Sedentary or sessile filter-feeding Marine and Freshwater or Terrestrial Head reduced Paired Gills No radula
Gastropoda Aquatic and terrestrial snails and slugs Marine, Freewater/terrestrial Usually has a shell Foot for locomotion Radula
Cephalopoda Predatory cuttlefish, squids and octopi. Marine Head surrounded by tentacles Tentacles usually have suckers External, internal or absent Shell Mouth with or without radula
Body Cavities o The body cavities in Mollusca are called mantle cavities (coelom), which are: /4_GB_23_AnimaliaInvert_Fig_f/BodyCavity_Coelom_29A.GIF o Water-filled cavities that house the gills, anus, and excretory pores. o There are also blood cavities known as hemocoel which store blood in open-circulatory mollusca.
Body Symmetry All mollusca have bilateral symmetry meaning… The organism can be cut in half with the two sides looking more or less exactly the same. Ex:
Nervous System nerv.jpg/medium.jpg Relatively complex nervous system, varies from species to species. All Mollusca have tentacles that have sensors to detect chemicals, vibrations and touch. Mollusca have ganglia, a sort of brain-like organ.
Circulatory System Other than cephalopods, all Mollusca have an open circulatory system These cavities are known as hemocoel, and in mollusks, it has replaced the coelem. Cephalopods need a closed- circulatory system because their activities require more energy. ges/bivalve_circulatory.jpg
Digestive System Radula to scrape up food Digestive tract is complete and ciliated Includes mouth, anus and complex stomach Food is taken up by the digestive glands arising from the stomach, where it is passed into the blood
Excretory System Waste is in solid form so it prevents the fouling of water over gills Excretory functions are regulated by a pair of nephridia and tubular structures Collect fluids from coleom and exchanges salts and substances with body tissues during excretion
Locomotion/Musculature Foot comprised of 3 main body parts – Viceral mass: contains interal organs – Mantle: fold of tissue over visceral mass, includes shell (if present – Mantle Cavity: houses gills and anus and excretory skills Herbivores are commonly gliders, move on muscular contraction Carnivores, more advanced locomotion – Cephalopods – Jet Propulsion – Cuttlefish/Sea Hares – Undulating later fins – Bivalves – Foot for burrowing
Skeletal System N/A BUT…………………………. They have shells made of calcium carbonate
Sensory Structures/Features Some mollusks have large complex eyes (notably the cephalopods) Squids can locate and capture transparent prey with specialized polarization vision.
Reproduction Sexual Reproduction External Fertilization: Sperm cell is united with egg cell away from the parents. Trochophore = Larvae Internal Fertilization Example: Land snails are hermaphrodites. They have a pouch for holding the sperm of the mate. ges/reproduction/mesomphix_inornaus_DD300.jpg l/ostrliv.gif 2_13Trochophore.jpg
Gas Exchange Generally takes place in the true gills (ctenidia) Absorbs the Oxygen from water and diffuses Carbon Dioxide into the water.
Unique Features Mantle: Encloses mantle cavity, which circulates oxygen and water. Radula: The mouth, with teeth bent inwards. Ctenidia Calcium Carbonate Shells _Squid_vs._Jet_Fighter-f1e6n4-d.jpg
QUIZ QUESTIONS!! 1. Which of the following phyla do not have symmetry? a. Mollusca b. Porifera c. Echinodermata 2. Which of the following classes of Mollusca need a closed circulatory system? a. Cephalopoda b. Bivalvia c. Gastropoda d. Polyplacophora
Quiz Questions (Cont.) 3. Excretory functions are regulated by… a. Nephridia b. Tubular structures c. Both d. Neither 4. Land Snails reproduce… a. Through internal fertilization b. Through external fertilization c. Sexually d. Asexually 5. Why don't they serve escargots at a McDonald's restaurants?
Answers 1. b 2. a 3. d 4. a 5. They only serve fast food