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Mollusca
Mollusca
Mollusca
Mollusca
Mollusca
Mollusca
Mollusca
Mollusca
Mollusca
Mollusca
Mollusca
Mollusca
Mollusca
Mollusca
Mollusca
Mollusca
Mollusca
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Transcript

  • 1. Mollusca
  • 2. Core Concepts
    • Mollusks, Phylum Mollusca, are-soft bodied animals that have an internal or external shell
    • Grouped together due to similar developmental pattern
    • Most of them have a special kind of ciliated larva called a trocophore that swim in open water and feed on tiny floating plants (phytoplanktons)
  • 3.
    • Trocophore larvae are seen in both mollusks and annelids which indicate that they evolved from a common ancestor (although segmentation was lost early in the evolution of mollusks)
  • 4.
    • Most adult members have:
      • bilateral symmetry
      • Open circulatory system (except cephalopods)
  • 5.
    • Body plan consists of four parts:
      • Muscular foot
      • Mantle
      • Shell
      • Visceral mass
  • 6.
    • Divided into 7-9 classes
      • 3 major classes
        • Class Gastropoda (snails, nudibranchs, slugs)
        • Class Pelecypoda (clams, oysters, mussels, scallops)
        • Class Cephalopoda (Squids, octopuses, cuttlefish)
  • 7. Keywords
    • Mollusca Malacology Pelecypoda
    • Gastropoda Cephalopoda mantle cavity
    • Trocophore larva mantle gills
    • Muscular foot internal/external shell
    • Visceral mass radula filter-feeder
    • Sinuses nephridia ganglia
    • Statocyst ocelli (eyespots)
  • 8. General Characteristics
    • Diversity: more than 150, 000 known species
    • Molluscus= soft
    • Soft-bodied animals with a muscular foot that usually contains the mouth and other structure associated with feeding
    • Mantle
      • Thin delicate cloak-like tissue layer that covers most of the mollusk’s body
  • 9.
    • Shell- calcareous (CaCO 3 ) secreted by mantle
    • Visceral mass- beneath the mantle
    • Mantle cavity- extension of the mantle; contains the gills, anus and excretory pore
    • Organ-system level of organization
  • 10.
    • Most adults have bilateral symmetry
    • Complete digestive system
    • Coelomate
    • Triploblastic
    • Open circulation (except cephalopod)
    • Classification: type of foot and kind of shell
  • 11. Digestive system
    • Mostly herbivores, carnovores, filter-feeders, few are detritus feeders and parasites
    • Radula- used for rasping or scraping or drilling to eat
    • Sharp jaws- use by octopuses to break shells
    • Use of poison
    • Filter-feeders- use of feathery gills (sometimes with mucus)
  • 12. Respiration
    • Use of gills or cutaneous respiration (skin)
    • Land snails and slugs- use mantle (High SA, rich in blood vessels)
  • 13. Circulatory System
    • Simple heart
    • Hemolymph (blood + interstitial fluid)
    • Open circulation (sessile)
      • Blood flows into spaces called sinuses
    • Close circulation (fast-moving)
  • 14. Excretory System
    • Nephridia- organ used to remove ammonia in their system
  • 15. Nervous System
    • Nerve ring- surrounds the esophagus
      • Where nerve cords extend
    • Simple nervous system (inactive bivalves)
      • Statocysts- balance
      • Ocelli- eyespots
    • Complex nervous system (intelligent predators)
  • 16. Reproduction
    • Separate sexes in most mollusks
    • Many hermaphrodites
    • External fertilization
    • Internal fertilization (tentacled mollusks, snails)
    • Sequential hermaphroditism
      • Change of sex depending on environmental factors
  • 17.  

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