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Mollusca
Paul Ko
Andy Zhao
Michael Chiu
Period 5
http://www.fossilmuseum.net/Tree_of_Life/PhylumMollusca/images/Nautilus-wpd.jpg
4 Major Classes:
•Polyplacophora
•Bivalvia
•Gastropoda
•Cephalopoda
http://upload.wikimedia.org/wikipedia/commons/a/a4/Ab_mollusca_01.jpg
Class Polyplacophora
• Chiton
• Marine
• Shell with Eight Plates
• Foot used for locomotion
• Radula
• No head
http://www.wallawalla.edu/academics/departments/biology/rosario/inverts/Mollusca/Polyplacophora/TonicellaLineataDLC1991.jpg
Bivalvia
• Clams and oysters
• Sedentary or sessile filter-feeding
• Marine and Freshwater or Terrestrial
•Head reduced
•Paired Gills
•No radula
http://www.korseby.net/outer/fauna/mollusca/bivalvia.jpeg
Gastropoda
• Aquatic and terrestrial snails
and slugs
•Marine, Freewater/terrestrial
•Usually has a shell
•Foot for locomotion
•Radula
http://upload.wikimedia.org/wikipedia/en/4/47/Banana_slug_closeup.jpg
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
http://static.open.salon.com/files/octopus1244124973.jpg
Body Cavities
o The body cavities in
Mollusca are called
mantle cavities
(coelom), which are:
http://www.southtexascollege.edu/nilsson/4_GB_Lecture_figs_f
/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:
http://chemistry.csudh.edu/faculty/jim/cozaugo4-600/octopus.jpg
Nervous System
•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.
http://animaldiversity.ummz.umich.edu/site/resources/biodidac/biva
nerv.jpg/medium.jpg
http://media.photobucket.com/image/cuttlefish/Nephlabobo/ComCuttlefish9.jpg
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 closedcirculatory system because
their activities require more
energy.
http://www.esu.edu/~milewski/intro_biol_two/lab__11_mollusca/ima
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
http://kentsimmons.uwinnipeg.ca/16cm05/1116/33-16-MolluskBodyPlan-L.gif
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
http://awakeningwomen.files.wordpress.com/2009/09/dumbo-octopus.jpg
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
http://www.ck12.org/ck12/images?id=113229
Skeletal System
N/A
BUT………………………….
They have shells made
of calcium carbonate
http://www.naturfoto-cz.de/photos/others/roman-snail-21973.jpg
Sensory Structures/Features
• Some mollusks have large complex eyes
(notably the cephalopods)
• Squids can locate and capture transparent prey
with specialized polarization vision.
http://www.news.wisc.edu/newsphotos/images/Hawaiian_bobtail_squid04.jpg
http://www.dlia.org/atbi/species/Animalia/Mollusca/Gastropoda/ima
ges/reproduction/mesomphix_inornaus_DD300.jpg
http://www.vattenkikaren.gu.se/fakta/arter/mollusca/bivalvia/ostredu
l/ostrliv.gif
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.
http://www.bobtherieau.com/images/blog/claM.jpg
http://www.nicertutor.com/doc/class/bio1903/Locked/media/ch32/3
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.
www.biol.wwu.edu/donovan/biol460/12mollusca.ppt
http://kentsimmons.uwinnipeg.ca/16cm05/1116/33-16-MolluskBodyPlan-L.gif
Unique Features
• Mantle: Encloses mantle cavity, which
circulates oxygen and water.
• Radula: The mouth, with teeth bent inwards.
Ctenidia
Calcium Carbonate
Shells
http://www.bio.miami.edu/dana/pix/ham.jpg
http://s3.amazonaws.com/wootdesigncontestentries/Shigwarm/Giant
_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
http://en.wikipedia.org/wiki/File:Tonicella-lineata.jpg
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?
http://biology.unm.edu/ccouncil/Biology_203/Images/Protostomes/squid.jpg
Answers
1. b
2. a
3. d
4. a
5. They only serve fast food 
Thank You
http://lair2000.net/Mermaids_Retreat/Research/kraken.jpg