Download Mollusks

Mollusks
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Classes: Bivalves, Snails, Cephalopods
Evolved from:
Segmentation:
Body zones:
1. How many mollusk species do exist today?
2. How is the shell produced?
3. What is the function of radula?
4. What is the speciality of scallops?
5. How large is the giant clam?
6. How do snails with no shells protect themselves?
7. How are cephalopods different from the other
mollusks?
• Body structure
– Head: sensory organs, mouth (radula)
– Foot: motor organ, skin grown together with
muscles
– Visceral hump: internal organs (digestive,
excretory, reproductive organs)
– Mantle: extension of the body wall, producing
exoskeleton (CaCO3 shell)
– Mantle cavity:
gills/lungs
• Circulatory system
– Open: blood moves through vessels into
open spaces around body organs
– Heart
– Arteries
– Veins
• Respiratory organs
– First animals having respiratory structures
• Nervous system:
– Ganglionic nervous system
• Reproduction:
– Usually separate sexes
– Usually external fertilization
Snails
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Terrestrial, freshwater, marine
Symmetry:
Shell: in one piece, (if no shell: slug)
Body zones:
Locomotion: belly footed
Respiration:
Feeding:
– Herbivorous, predators
– Radula
• Sense organs: tentacles, eyes
Bivalves
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Aquatic
Symmetry:
Shell:
Body zones:
Locomotion:
Respiration:
Feeding:
– filter-feeders
• Sense organs:
Cephalopods
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Most complex, most recently evolved
Marine
Symmetry:
Shell: no, or pen
Body zones:
Locomotion:
Respiration:
Feeding:
Circulatory system: closed
Sense organs: