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Phylum Mollusca

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... use a radula to scrape algae from rocks Carnivores use jaws to eat prey like the octopus Filter feeders use a siphon to catch plankton Gas exchange via ... – PowerPoint PPT presentation

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Title: Phylum Mollusca


1
Phylum Molluscasoft-bodied
2
  • 4 Primary Classes
  • Class Gastropoda Snails, conchs, slugs, sea
    slugs, sea hares, limpets, etc. (very diverse)

3
Gastropoda stomach-footedSnails and slugs
4
Class Bivalvia Clams, oysters and scallops
5
Bivalvia two halvesClams, oysters, scallops,
mussels
6
Class Cephalopoda Octopi, squid, nautilis,
cuttlefish
7
Cephalopoda head-footedOctopi, cuttlefish,
squid, nautali
http//www.youtube.com/watch?featureplayer_detail
pagevYVvn8dpSAt0
8
Blue-Ring Octopus
9
(No Transcript)
10
(No Transcript)
11
Cuttlefish
12
(No Transcript)
13
Squid
14
Giant SquidAvg. length35 feet Max.
Length80 feet
15
Colossal SquidMaximum length43 feet
16
http//www.ted.com/talks/david_gallo_ shows_underw
ater_astonishments.html
17
Class Polyplacophora Chitons
18
Body plan
  • Bilateral Symmetry
  • Muscular foot used for locomotion, burrowing and
    capturing prey
  • Mantle, an outgrowth of tissue that covers
  • most of its body. This secretes the shell.
  • Coelom -Body cavity primarily around heart
  • Shell - Made of calcium carbonate, internal or
    external
  • Viceral mass the internal organs

19
Feeding
  • Complete digestive system
  • Herbivores use a radula to scrape algae
  • from rocks
  • Carnivores use jaws to eat prey
  • like the octopus
  • Filter feeders use a siphon to catch plankton

20
Respiration
  • Gas exchange via gills, lungs
  • Land snails respire through a mantle or its body
    surface

21
Circulation
  • Open circulatory system- except cephalopods,
    where the blood is transported through the body
    via a cavity called the hemocoel
  • Leaving the vessels, blood travels through
    sinuses or large sack-like spaces
  • Possess blood vessels by a heart
  • Fast moving mollusks have a closed circulatory
    system using blood vessels

22
Excretion
  • Tube shaped nephridia remove ammonia from the
    blood and release it outside the body

23
Response
  • Nervous system varies greatly. Other than
    cephalopods, it is very basic. Several ganglia in
    clams and bivalves
  • Cephalopods have a highly developed brain and
    nervous system, near equal to vertebrates.

24
Movement
  • Some secrete mucus
  • Others like the octopus move by jet propulsion

25
Reproduction
  • Reproduction is sexual by external fertilization
    as in snails and bivalves
  • Some are hermaphroditic like the snail

26
Ancestry of Molluscs
27
Phylum Significance
  • Eaten for food by humans and other animals.
    Clams, oysters, scallops, mussels, (shellfish)
    snails (escargot), octopus and squid are popular
    foods
  • Research - i.e. snails appear to be cancer free
  • Indicators of environmental pollution
  • Land snails and slugs damage gardens and crops
  • Shipworms destroy wooden boats, docks, and piers.
  • Filter feeders can concentrate toxins through
    biological magnification (Humans eating them can
    become ill or even die).
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