Spiralians 2: Mollusca (Chapter 13)

Question 1

Mollusca

Answer 1

• phylum assigned for usually unsegmented, soft-bodied animals
• body plan based on 4 features:
  
  • radula
  • feet
  • visceral mass
  • mantle
• slugs, snails, cuttlefish, octopuses, clams, mussels, & oysters

Question 2

Radula

Answer 2

• rasping feeding organ
• act as scrap & drill
• composed of chitin

Question 3

foot of mollusks

Answer 3

• sole-like structure
• initially used for crawling → modified in some classes

Question 4

visceral mass of mollusks

Answer 4

celonic cavity containing digestive, excretory, reproductive, & circulatory organs

Question 5

mantle of mollusks

Answer 5

• sheet of tissues overlying visceral mass
• responsible for secreting shells

Question 6

Monoplacophora

Answer 6

• class of phylum Mollusca
• limplet-like
• segmented body parts
• poor fossil record after Paleozoic
• thought to be extinct until found in deep sea environment in 1950s
• Cambrian to Recent

Question 7

Polyplacophora

Answer 7

• class of Phylum Mollusca
• segmented shell (usually 8)
• large muscular foot
• series of gill pairs
• marine but can be found in intertidal zones (able to survive when exposed to air)
• sporadic fossil record - rare articulate specimens
• Cambrian to Recent

Question 8

Scaphopoda

Answer 8

• class of phylum Mollusca
• long, cylindrical shell with openings at both ends
• marine, usually infauna
• sporadic fossil record (minor part of fossil assemblage)
• Devonian to Recent

Question 9

“H.A.M.”

Answer 9

• Hypothetical Ancestral Mollusk
• an organism ancestral to all diverse classes of Mollusca
• all four noted features
• resemble a flatworm with 2 shells & smaller sclerite plates