Class Notes (806,882)
Canada (492,497)
Biology (Sci) (2,417)
BIOL 111 (283)
Lecture 13

Mollusks- How the Nervous System Works (Lecture 13)

9 Pages
Unlock Document

McGill University
Biology (Sci)
BIOL 111
Irene Gregory- Eaves

Biology Lecture 13: Mollusks- How the Nervous System Works 10/19/2011 5:21:00 PM Phylum Mollusca “mollusks”, “shellfish”  >100,000 species  2 largest animal phylum  terrestrial or aquatic  highly diverse: - morphology - modes of nutrition - reproduction - response to the environment  bilaterally symmetrical, triploblastic  coelomate protostomes  trochophore larvae (marine mollusks)  major groups: - Class Polyplacophora - Class Gastropoda - Class Bivalvia - Class Cephalopoda  variations on an ancestral molluscan body plan Mollusk Body Plan 1. Foot 2. Mantle 3. Visceral Mass  contains gills (aquatic)  acts Mollusk Body Planrial) 1. foot 2. mantle 3. visceral mass shell Mollusk Body Plan radula heart anus 1. foot mouth. mantle 3. viscegillsass mantle cavity 11 mantle cavity visceral mass foot • contains gills (aquatic); acts as lung (terrestrial) 10 Class Polyplacophora “many plates”  segmented shell (8 overlapping plates)  multiple gills  omnivorous - radula scrapes algae & bryozoans  large muscular foot  ability to roll into a ball  gills located in mantle grooves  ex: chiton –common to intertidal zones Class Bivavlvia “two valves”  reductioClass Bivalvia “two valves”  hinged shell • renlargement of foot• mantle cavity modified • hinged shell by siphons  mantle cavity modif• enlargement of gill • enlargement of foot  enlargement of gill foot 14 Bivalves  relatively sessile  filter feeders  broadcast spawners  siphons - extensions of posterior mantle - water flows in mantle cavity and then across gills that act as filters for food  foot used as anchor and for digging  ex: scallop - large adductor muscles to close shell - mantle lined eyes—can detect motion and light Class Gastropoda  most diverse class (70,000 species)  terrestrial or aquatic  shelled (snails) or shell-less (slugs, nudibranchs)  herbivores, predators, scavengers  more complex head and eyes  internal or external fertilization  either dioecious or hermaphroditic but can produce only sperm or eggs at one time Gastropods Gastropods “stoma“stomach foot”  torsion (twisting) of body • torsion (twisting) of body - 180 degrees rotation of visceral mass – 180- romantle cavity, anus moved over head – mantGastropods undergo torsion head  coiling of visceral mass  they undergo torsion • coiling of visceral mass 18 19  then elongation and coiling  ex: cone snail—radula modified into toxic harpoon, nudibranch “naked gill”—warning coloration (aposematic) and some prey on tentacles of cnidarian polyps, land snails—eyes on tips of tentacles Class Cephalopoda “head foot” Class Cephalopoda “head foot”  •subdivided foot—arms, tentaclesles  •enlarged head, reduced shelll tentacle 25 Chepalopods – as predators  predators have excellent vision (lens)  complex behavior - visual communication with color and texture (chromatophores)  ink sac—defense  closed circulatory system  mantle and siphon used for jet propulsion  arms with suckers and/or hook—some have 2 elongated tentacles Chephalopods—reproduction  separate sexes with elaborate courtship  internal fertilization, where males transfer sperm via specialized arm= hectocotylus  females die after laying eggs or after eggs hatch  no trochophore larva  ex: nautilus: - 80-90 arms - regulate buoyancy with gases in chambered shell - only extant shelled cephalopod  ex: ammonite - dominant invert predator (300 mya) - extinct at end of Cretaceous (65 mya) Mollusks  economically and culturally important - food (shellfish) - jewelry (pearls, abalone) - vectors for parasites (snail: blood fluke) - exotic invasions (zebra mussel)  neurological research squid neurons - giant squid nerve cells can be up to 1 mm in diameter—specialized for fast movement Nervous Systems Nervousfunction: receive, process, & relay information  function: receive, process, and relay information Nerve net Ganglia Central nervous system nerves Peripheral nervous system (CNS) &(PNS) Nervous System • Composed of two different types of cells: – 1) Neurons = generate and transmit electrical signals (aka nerve impulses) – 2) Glial cells = support neurons by providing 32 nutrients, maintain extracellular environment & insulate neurons Axon = part of
More Less

Related notes for BIOL 111

Log In


Don't have an account?

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.