Post on 18-Dec-2015
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.