(2) Mollusca

Question 1

General Characteristics

Answer 1

1. Eucelomate
2. Foot - locomotion
3. Mantle - pair of thin body folds
   4.Radula - rasping moutpart
4. Open circulatory system (closed in cephalopods)
5. Respiration - cutaneous, gills, vascular mantle, blood capillaries (lungs)
6. Organ system level of organization
7. Extracellular digestion

Question 2

Head-foot

Answer 2

a). Head
-mouth with radula- toothed, rasping tongue
- sensory organs concentrated on the head
b). foot-locomotion
c). MOST bivalves lack a head and radula; filter feed

Question 3

Visceral Mass

Answer 3

soft body houses organ systems

Question 4

Mantle

Answer 4

thin fleshy sheath hanging down either side of body
-it protects

Question 5

Three Layers of Shell

Answer 5

Outer: periostracum
Middle: prismatic
Inner: nacreous

Question 6

Periostracum (outer)

Answer 6

resists acids, attack, camouflage

Question 7

Prismatic (middle)

Answer 7

CaCO3 for strength

Question 8

Nacreous (inner)

Answer 8

smooth mother-of-pearl to protect soft body

Question 9

Mantle Cavity

Answer 9

-encloses gills or serves as lungs
-digestive, excretory, and reproductive products brought here

Question 10

Open circulation

Answer 10

-blood oxygenated in gills and mantle
-goes to paired auricles of heart -> muscular ventricle: 3 chambers
- tissues bathed within coelom
-blood collected and pressure boosted by accessory hearts in front of each gill

Question 11

Polyplacophora

Answer 11

Chitons
-dorsoventrally flattened; 8 overlapping protective plates on top
-clings to rocks, scrapes, algae
-90,000 species

Question 12

Gastropoda

Answer 12

-land and sea slugs
-most diverse mollusk class
- only mollusk class with terrestrial forms
- coiled univalve shell (or absent)

Question 13

Torsion (Gastropoda)

Answer 13

during embryonic development body is twisted 180 degrees, orientating anus anteriorly; advantage not clear

Question 14

Feeding (Gastropoda)

Answer 14

a). Herbivorous - grazers of algae, plants
Ex. Snails
b). Suspension/filter- trap food particles in mantle mucous
Ex. Limpets
c). Scavengers - grazers of algae, plants
Ex. some snails
d). Carnivorous
Ex. Oyster drill

Question 15

Respiration (Gastropoda)

Answer 15

• Gills- conchs, whelks
• Vascular Mantle (lung) - terrestrial snails, slugs

Question 16

Bivalvia “two shells”

Answer 16

mussels, scallops, oysters, shipworms
a). two laterally compressed shells
b). no hear or radula

Question 17

Respiration (Bivalvia)

Answer 17

cilia create water current -> incurrent siphon -> gills -> outcurrent siphon

Question 18

Filter Feeding (Bivalvia)

Answer 18

1. food trapped by mucous covered gills
2. Cilia carry to labial -> mouth
3. Shipworms rasp wood with shell, bacteria in gut provide cellulase

Question 19

Locomotion (Bivalvia)

Answer 19

foot extended, burrows in sand, swells with blood and anchors, body pulled forward

Question 20

Glochidium (Bivalvia)

Answer 20

specialized veliger larva, parasite disperses on fish gills, scales

Question 21

Cephalopods

Answer 21

squids, octopus, cuttlefish, nautilus
a). Most have NO shell; a narrow internal chitin strip protects ganglia
b). foot as arms/tentacles in head region
c). jet propelled- water forced out
d). highly predatory; advanced eyes
e). advanced social communication
- chromatophores change color rapidly
f). closed circulation

Question 22

Reproduction (Cephalopods)

Answer 22

males place spermatophore in female using arm; fertilised eggs attach to stones