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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.