Mollusks bivalves:gastro
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Transcript of Mollusks bivalves:gastro
Phylum Mollusca
Class: Gastropoda
Class: Bivalvia
Characteristics of Mollusca
• Protosome characteristics
• Coelom surrounds heart
• Open circulatory system (except cephalopods)
Class Gastropoda
Snails, Limpets and Slugs
Gastropoda• Planning on being rich and
famous?• Wining and dining at the
most expensive restaurants?
• Romantic trips to Paris? • Ever wonder what Ceaser
munched on after long hard days ruling the roman empire?
• Than you should be familiar with ESCARGOT!!!!
General Body Plan: Gastropod
• 1. Head foot• Head: sensory nerves,
mouth – Anterior: near the
head/mouth
• Foot: attachment and locomotion – Posterior: near the anus– Flattened w Cilia:
locomotion
That slimy foot… • Snail Slime:
– Suction power: travel up and down trees
– Escape: Emit a nasty tasting slime when threatened
– Movement: Allows them to easily squeeze through tight spaces
– Water Retention
• How Ms. Cota looks so young: – Skin regenerating – used in skin beauty products
General Body Plan: Gastropod
• 2. Visceral Mass– Organs of
digestion – Circulation – Reproduction – Excretion – Dorsal to the
head foot
General Body Plan: Gastropod
• Mantle (shell) – Attached to visceral
mass• Encloses most of the
body
– Protection
• Mantle Cavity: – Gas exchange– Elimination of digestive
wastes – Release of reproductive
products
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
General Body Plan: Mollusca
• Radula: Scraping mouth – Chitinous belt & curved
teeth • Covers fleshy tongue • Muscles move it back
and forth • Conveyor belt
• Digestion – Scrape algae– Enzymes break down
food in stomach
CFU
• How do mollusks exchange gasses – Filter air through their gills
• Where are these gills located?– The mantel
• What is the structure called that scrapes up food?– A Radula
• All mollusks have: – A visceral Mass – A head foot – A mantel
Gastropoda
• Marine, Freshwater, Terrestrial
• Signifying feature: Torsion
Tosion
• 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
Torsion
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
CFU
• What is Torsion?– The 180 degree twisting of internal organs
in snails
• How is Torsion adaptive? – Pulls head in first, seals opening, locates
all sensory nerves in the front
Class Bivalvia
Clams, Oysters, Mussles, Scallops
Bivalvia!
• 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
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
• Most mollusks have foot that can be used differently – Attach mollusk to
surface – Act as a lure to
attract prey – Surround organs for
safety
Respiratory System
• Respiration: Cilia in gills move water into mantel cavity – Water tubes
exchange water to blood through diffusion
– Water exits bivalve
Digestive System
• Food comes in through gills – Sorted – Digested – Waste forcibly
pushed out of mantel cavity by valves shutting quickly
Human Interaction
• Many, many mollusks are threatened or endangered– Over harvesting– Pollution– Loss of habitat – Loss of water
currents
CFU • What is the technical term for the two halves of the
shell?– Valves
• What structure filters water in and out of the shell – Siphon
• What is the function of the foot – Attach mollusk to substrate, act as lure
• Why are bivalves important to humans?– Pearls, food source, pollution filter
• How are humans affecting bivalves? – Over harvesting, pollution, loss of current
Get ready for dissecfrtion!