Transcript Phylum Mollusca: Mollusks

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Quite a diverse group
Includes snails, slugs, clams, squids, and octopi
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Soft bodied
animals
Most have
bilateral
symmetry
Usually have
an internal or
external shell
secreted by a
layer called
the mantle
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Mantle – thin layer of
tissue that covers most
of the mollusks body
Foot – contains feeding
structures (may be flat
for crawling, spade
shaped for burrowing,
or as tentacles for
capturing prey)
Shell – used for
protection; composed
of calcium carbonate
Visceral Mass –
internal organs
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Contain simple kidney-like organs to carry
out excretion
Gets rid of nitrogenous wastes (wastes from
broken down proteins and cell parts)
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Aquatic
mollusks breathe
using gills
Terrestrial
mollusks breathe
by diffusion
through skin of
the mantle
cavity that is
lined with blood
vessels
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Have a digestive system with two openings:
mouth and anus
Feed in a variety of ways
May have an open or closed circulation:
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Open Circulation – blood is pumped through
Blood stays in
vessels fromBlood
heart
dumpsto
intoa saclike sinus. It then
vessels and
an open area and
never comes
passes through
gills
for
gas
exchange
and
surrounds the body
in direct
contact with
finally backcells
to heart.
the body
cells.
Closed Circulation – blood is pumped around
Open
Closed
the body by a heart but the
blood remains
Circulation
Circulation
inside
blood
vessels,
similar
to a human.
Plan
Plan
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Source
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Clams and other two
shelled mollusks have a
simple nervous system
with a few nerve cords
and sense organs
Octopi and their relatives
have the most highly
developed nervous
system of all
invertebrates; they can
actually learn and
remember certain
behaviors!
Source
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Many snails and two-shelled mollusks
reproduce utilizing external fertilization; large
amounts of sperm and eggs are released into
the water
Certain snails and tentacled mollusks use
internal fertilization
Still others are hermaphrodites and fertilize
eggs of another individual
Based on characteristics of foot and shell
 Gastropods – pond snails, slugs, sea hares, etc.
(shell-less or single shelled and move using
muscular foot)
 Bivalves – clams, oysters, mussels, and scallops
(have two shells held together by muscles)
 Cephalopods – octopi, squids, nautiluses, and
cuttlefishes (soft-bodied, head is attached to
foot which is divided into tentacles or arms)
Source
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http://photos21.flickr.com/32523124_981521b
b8a.jpg
http://video.nationalgeographic.com/video/p
layer/animals/invertebrates-animals/octopusandsquid/octopus_giant_kills_shark.html?source=
G2101&kwid=shark|929542585