most mollusks have shells & echinoderms have spiny skeleton mollusks are soft-bodied animals...

8
Most Mollusks have shells & Echinoderms have spiny skeleton • MOLLUSKS ARE SOFT-BODIED ANIMALS • MOLLUSKS SHOW A RANGE OF ADAPTATIONS • ECHINODERMS HAVE UNUSUAL ADAPTATIONS

Upload: thomas-obrien

Post on 18-Dec-2015

219 views

Category:

Documents


0 download

TRANSCRIPT

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.