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.