Transcript Most Mollusks have shells & Echinoderms have spiny skeleton

Most Mollusks have shells &
Echinoderms have spiny
skeleton
• MOLLUSKS ARE SOFT-BODIED
ANIMALS
• MOLLUSKS SHOW A RANGE OF
ADAPTATIONS
• ECHINODERMS HAVE UNUSUAL
ADAPTATIONS
Mollusks: soft-bodied animals
• All mollusks have soft shell; many
have outer protective shell.
• All mollusks have a muscular foot
(head is actually attached to its foot);
and all mollusks have a mantle (layer
of folded skin that protects its internal
organs).
• Oyster, clams, snails, mussels are
mollusks; so are squid, octopus, &
slugs
• Live on land & water environments
• Most have well-developed organ
systems.
• Reproduce sexually
Mollusks: Bivalves
• Have hard shell of 2
matching halves (clam,
mussel, oyster)
• Are filter feeders, filter
food from surrounding
water; bivalve moves by
pushing foot in & out.
• Takes in oxygen by pair of
gills (organ that filters
dissolved oxygen from
water); in most bivalves,
gills also filter food.
Gastropod Mollusks
• Gastropods protect
selves by withdrawing
into shells.
• Head is at end of its foot;
has eyes & tentacles for
sensing; some have a
radula(cutting mouth part
to shred food)
• Some eat animals, most
feed on plants & algae
• Some have gills (& live
in water); some have
lungs (& live on land)
Cephalopod Mollusks
• Live in saltwater (octopus, squid, &
chambered nautiluses). Well
developed body systems.
• Brain & nerves, eyes near mouth,
tentacles for capturing prey..
• Mantle can push water forcefully
thru a siphon to move animal.
• Gills take in oxygen, which goes
into blood & pumped (3 hearts)
• Most have no protective shells, but
protective behavior (may change
color, squirt ink, move quickly)
• Nautilus has shell, but made of
separate chambers (inner filled with
gas to help float-live in outer
chamber)
Mollusks: range of adaptations
• Even though clam and octopus seem very different,
still classified as mollusks.
• Foot of bivalve is simple muscle moving in & out of
shell to help move; gastropods have head at end of
foot & muscles in foot let it glide over surfaces;
cephalopods have tentacles on foot to pull food into
its mouth and to move along the ocean floor.
Echinoderms:strange adaptations
• Invertebrates that live in ocean,
have radial symmetry as adult
(sea star, s.urchin, s.cucumber,
sand dollars);
• Feed off ocean floor (mouth at
center of body underneath);
some filter food, others prey on
clams,snails,& other
echinoderms.
• Means “spiny-skinned” (some
have larger spines than others)
• Have skeletons of stiff plates
just under their skin. Some are
loosely connected for more
movement (sea star), while
others grow close together for
less flexibility (sand dollar)
Echinoderms:strange adaptations
• Echinoderms have a water vascular system of water-filled
tubes, radiating out from center; water comes in from
openings on upper surface, to feed into tubes
• Muscles attach to top of tube to shut off water, causing
suction at base of tube where “feet” are; tube feet stick to
ocean floor to move it around.
• Tube feet can also hunt prey, grab it and pull open shells. (sea
star then pushes stomach out thru mouth into bivalve’s shell
to digest it’s body)
• Not all echinoderms hunt, sea urchin eats algae on ocean
floor.