Molluscs Flashcards
(26 cards)
What are the three main body parts of molluscs?
Visceral mass (internal organs), foot (locomotion), mantle (body covering that secretes the shell)
What is the radula and its function?
A belt-like structure with rows of teeth used for scraping, cutting, boring, and conveying food.
What type of circulatory system do molluscs have?
Most have an open circulatory system with a heart; cephalopods have a closed system.
How do pulmonate molluscs respire?
Through a lung-like mantle cavity adapted for gas exchange in air.
What is characteristic of Aplacophora?
Lack shell, mantle, and foot; worm-like, marine, with calcareous spicules.
What defines Polyplacophora (chitons)?
Have 8 overlapping shell plates, slow-moving microphagous grazers with radula, clamp tightly to rocks
Where do Monoplacophora live and what is unique about them?
Deep-sea environments (>2000 m); possess a single symmetrical shell
What is unique about Gastropoda?
Largest class; many have spiral shells, includes slugs, snails, limpets
What is the function of the pneumostome in Pulmonata?
A pore for gas exchange; reduces water loss in terrestrial gastropods.
What characterizes Bivalvia?
Two-valved shell, no head or radula, filter/deposit feeders, use adductor muscles to close shell.
What are captacula in Scaphopoda used for?
Sticky tentacles used to capture microscopic prey
How do cephalopods move?
By jet propulsion using a siphon
What adaptations make cephalopods advanced?
Complex eyes, chromatophores, bioluminescence, ink sac, powerful beak.
How does Nautilus differ from other cephalopods?
Has an external coiled shell with internal chambers, many tentacles, no suckers
What defines Coleoidea subclass?
Includes squids, octopuses, and cuttlefish; shell reduced or internal
What is distinctive about Sepiida (cuttlefish)?
Have a broad body with lateral fins, internal shell (cuttlebone), and complex colour patterns.
How are squids (Teuthoidea) adapted for speed?
Streamlined body, efficient jet propulsion, internal blade-like pen.
What characterizes Octopoda?
Eight arms, benthic lifestyle, highly intelligent, reduced shell.
What is the purpose of the Argonaut (paper nautilus) eggcase?
Buoyancy control and brooding; secreted only by females, paper thin-eggcase - not a true shell
What is torsion in gastropods?
A developmental process causing the visceral mass to rotate, positioning the anus over the head
What are nudibranchs?
Benthic gastropods (sea slugs) with external gills and often no shell; many are brightly colored
What is the feeding mechanism of bivalves?
Use gills or siphons to filter microscopic food; cilia transport food to the mouth.
What defines class Scaphopoda (tusk shells)?
Tubular shell open at both ends, no gills, gas exchange via mantle, captacula tentacles
What are chromatophores used for in cephalopods?
Pigment cells used to change color for camouflage, communication, or display.
