c hapter 9 mollusks
DESCRIPTION
TRANSCRIPT
Phylum Mollusca
Class: Gastropoda
Class: Bivalvia
Class: Cephalopoda
Class Gastropoda
Snails, Limpets and Slugs
General Body Plan: Gastropod
• Characteristics– 1. Head foot
• Head: sensory nerves, mouth • Foot: attachment and locomotion
General Body Plan: Gastropod
2. Visceral Mass– Organs of
digestion – Circulation – Reproduction – Excretion – Dorsal to the
head foot
General Body Plan: Gastropod
3. Mantle (shell) – Attached to visceral
mass• Encloses most of the
body – Protection
4. Mantle Cavity: – Gas exchange– Elimination of digestive
wastes – Release of reproductive
products
That slimy foot… • Snail Slime:
– Escape– Movement– Water Retention
• Ecological Roles: – Skin regenerating – used in skin beauty products
• http://www.youtube.com/watch?v=JhRwcPRy6l4&safety_mode=true&persist_safety_mode=1&safe=active
Respiration
• One Gill in mantle cavity – Oxygen is taken in – Diffused through the cells
• Open Circulatory System – Pushes blood in to
expand– Pulls it out to contract
• Digestion – Scrape algae– Enzymes break down
food in stomach
• Radula: Scraping mouth – Chitinous belt & curved
teeth • Covers fleshy tongue • Muscles move it back
and forth • Conveyor belt
Torsion
• Benefits – Head enters first:
protection – Operculum seals
opening to prevent drying out
– Allows clean water to enter mantle cavity
– Makes snail more sensitive to stimuli coming from the front
Reproduction
• Monoecious: can be whatever sex they want! – Internal cross
fertilization – One snail acts as
female one acts as male
– Deposit eggs in gelationous strings
Class Bivalvia
Clams, Oysters, Mussles, Scallops
Structure
• Two halves of a shell: Valves – Adductor muscles hold
valves shut • Visceral Mass• Mantel Cavity• Gills • Cilia• Siphon:
– filters water in and out of shell
Foot
– Attach mollusk to surface
– Act as a lure to attract prey
– Surround organs for safety
Ecological Roles
• Edible• Commercial value:
Form Pearls • Valuable in removing
bacteria from polluted water! – Rely on water currents to
get food – Filter in nutrients, filter
out clean water • Valuable food source:
humans, raccoons, otters, birds
Digestive System
• Food comes in through gills – Sorted – Digested – Waste forcibly
pushed out of mantle cavity by valves shutting quickly
Respiratory System
• Respiration: Cilia in gills move water into mantel cavity – Water tubes
exchange water to blood through diffusion
– Water exits bivalve
Human Interaction
• Many, many mollusks are threatened or endangered– Over harvesting– Pollution– Loss of habitat – Loss of water
currents
Mollusks: Cephalopods Octopus, Squid, Cuttlefish
Physical Characteristics
• Anterior– Tentacles and jet
propulsion • Mantle (Shell)
– Nautilus: only cephalopod w external shell
• Fills it with gasses to help w buoyancy
– Squid: internal shell, helps with structure
– Octopus: NO SHELL
Locomotion
• Jet like propulsion out of mantle – Squid: uses it for
catching prey • Up to 25 mph!
– Octopus: escape method
ECOLOGICAL ROLE
• Fierce Predators – Large brains – Complex sensory structures – Rapid locomotion – Grasping tentacles
• http://www.youtube.com/watch?v=p9A-oxUMAy8&safety_mode=true&persist_safety_mode=1&safe=active
Digestion
• Enzymes digest food in stomach– Moves to anus– Expelled during
jet propulsion
Giant Squid Dissection
• http://www.youtube.com/watch?v=d83nSFEoz2A&safety_mode=true&persist_safety_mode=1&safe=active
Predator Adaptations
• Locate prey by sight• capture prey w
tentacles/ suction cups – Tentacles reinforced w
protein
• Eat using a radula – Cuttlefish: small
invertebrates – Octopus:
• Nocturnal: snails, fish, crustations
Predator Adaptations
• Chromatophores – Cells that can change colors
• Tiny muscles contract or expand and chromatophores quickly change color– Alarm response– Defensive – Blend in w environment– Courtship – Bioluminescence
• http://www.youtube.com/watch?v=t-LTWFnGmeg&feature=related&safety_mode=true&persist_safety_mode=1&safe=active