chapter 7: mollusks - ms. murray's biology -...
TRANSCRIPT
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Mollusks Soft-bodied Invertebrates
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Very diverse - more species of molluscs than any other group in the ocean.
Phylum includes:
Bivalves (2 shells); ex. Clam
Gastropods (1 shell, coiled); ex. Snail
Cephalopods (large head, tentacles); ex. Octopus
Phylum Mollusca
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K P C O F G S
Class Bivalvia (clams, mussels)
Class Gastropoda (snails)
Class Cephalopoda (octopus, squids)
Phylum Mollusca
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Soft-bodies
Calcium carbonate shell
Mantle (thin layer of tissue that covers the body)
Mantle secretes the shell
Bilateral symmetry (most)
Muscular foot (movement)
Head with sensory organs
Paired gills (O2 exchange)
Radula (tool used to feed,
scrapes surfaces)
Phylum Mollusca
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Approx. 10,000 species
Bodies are bilaterally symmetrical, laterally compressed
Have head, foot, coiled visceral mass (internal organ)
Mantle: membrane that lines the inside of the shell; contains glands that release calcium carbonate.
Clams live buried in sand; intertidal and subtidal zones.
Bivalvia
clams, mussels, oysters, scallops
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Body is enclosed within a shell
2 shells (valves) Valves hinged at one end.
Umbo is hump at dorsal (top) side of shells, near hinge Umbo is the oldest part of the shell
Growth of shell is from umbo – growth lines/rings show on shell.
No head, no radula
Gills: exchange oxygen and filter food particles from water.
Adductor muscles keep shells closed.
Bivalvia
clams, mussels, oysters, scallops
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http://www.nbcnews.com/video/nightly-news/53547313#53547313
World’s Oldest Animal: a clam!
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Shells are shut tight; only a small gap between them.
Siphon tube sticks out from gap to feed and breathe.
Incurrent (IN) and outcurrent (OUT) openings
Water moves IN (food particles and O2)
Water moves OUT (waste from digestion and CO2)
Bivalves are filter feeders: water comes in through the siphon and washes over gills – food particles get stuck on gills and mantle and are then moved toward the mouth.
Bilvalve Feeding
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Breathe using gills: water flows over gills - O2 comes in, CO2 goes out
Open circulatory system transports oxygen through a colorless blood.
Bilvalve Breathing
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Bilvalve Reproduction
Reproduction is external: eggs and sperm are released into the water.
Temporary zooplankton: larvae are planktonic.
When shells are formed, they sink to the bottom and develop into adults.
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Bivalve Diversity
Not all bivalves burrow in sand
Mussels: use byssal threads (protein fibers) to attach themselves to rocks, other surfaces.
Oysters: cement themselves to shells of other oysters.
Scallops: some species swim by clapping their shells together (one very strong adductor muscle)
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Clam – external features
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Clam – internal features
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K P C O F G S
Class Bivalvia (clams, mussels)
Class Gastropoda (snails)
Class Cephalopoda (octopus, squids)
Phylum Mollusca
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Two-thirds of all mollusks are gastropods.
80,000-100,000 species (mostly marine)
Univalves: one shell – it is usually spiral or coiled.
Gastropoda means “stomach-foot”.
Gastropods: snails and slugs
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Large muscular foot is used to move on surfaces.
Radula is used to scrape food from rocks.
Food is taken in through the mouth and moves down a one-way digestive tract; waste is sent out through the anus.
Gastropod Feeding
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Nutrients are transported using an open circulatory system:
Heart pumps blood through tissue when it contracts.
Kidneys: filter and send out waste from cells.
Operculum: trapdoor over shell’s opening.
When not feeding or moving, snails close up into their shells.
Gastropod Feeding
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Gastropods: snails and slugs
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Some species have separate sexes.
Some species are hermaphrodites (both male & female)
Internal fertilization: egg is fertilized INSIDE the organism.
External development: fertilized eggs can be deposited into the water OR eggs may develop in an egg case.
Many snail larvae are planktonic.
Gastropod Reproduction
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APEX: first part of shell formed; oldest.
WHORL: one complete coil of the shell.
BODY WHORL: last part of shell formed; youngest.
MOUTH: opening of shell.
LIP: thickened edge of mouth.
SPIRE: all visible whorls, not including body whorl.
Shell Morphology
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Gastropod Anatomy
STRUCTURE FUNCTION
Shell Protection
Muscular foot Movement
Anterior antennae (eyes) Vision
Posterior antennae Sensitivity
Siphon Water intake
Gills Breathing/gas exchange
Radula Feeding/ingestion
Mouth, stomach, intestines, anus One-way digestion
Kidney Filtration & Excretion
Heart Nutrient transport
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Gastropod Morphology
APEX: ________________________ _____________________________.
WHORL: ______________________ _____________________________.
BODY WHORL: ________________ _____________________________.
MOUTH: _____________________.
LIP: _________________________.
SPIRE: _______________________ _____________________________.
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Gastropod Anatomy
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Gastropod Anatomy
STRUCTURE FUNCTION
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http://shapeoflife.org/video/molluscs-survival-game
http://shapeoflife.org/video/geerat-vermeij-evolutionary-biologist-reading-shell%E2%80%99s-story
Molluscs
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K P C O F G S
Class Bivalvia (clams, mussels)
Class Gastropoda (snails)
Class Cephalopoda (octopus, squids)
Phylum Mollusca
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800 marine species
Prominent head and tentacles
Cephalopoda means “head-foot”.
Cephalopoda: squid, octopus, cuttlefish
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Swimming mollusks: swim by jet propulsion
Streamlined body shape
No external shell (shell is either lost or very reduced)
Draw water into mantle and then contract mantle to send water out of the water jet/siphon – propels through water.
Can direct themselves by changing the direction of the water jet (coordinated by a highly developed nervous system).
https://www.youtube.com/watch?v=eT8sNJp9yOw
Cephalopoda: squid, octopus, cuttlefish
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“Foot” of Cephalopods is modified into arms & tentacles Tentacles: capture prey (fish, crabs) Animal is killed with their beak.
Octopus also paralyzes with venom
Complex nervous system.
One-way digestive tract (mouth anus)
Closed circulatory system transports nutrients.
Cephalopoda: squid, octopus, cuttlefish
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Squid: long, thin internal shell (“pen”) Fastest cephalopod; swims in large schools (gives protection) 8 arms, 2 tentacles
Octopus: no remaining shell (some may have vestigial remnants) Solitary, efficient hunters (use beak, also venom in some sp.) 8 arms
Cuttlefish: internal shell(cuttlebone) 8 arms, 2 tentacles solitary organism
Nautilus: large external shell solitary organisms. 60-90 short tentacles
Cephalopoda: squid, octopus, cuttlefish
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Camouflage: adaptation to avoid predation.
Special pigmented cells (chromatophores) change shape in skin and allow animal to blend in.
Ink: cephalopods use cloud of ink to confuse predators, allowing them to escape.
Highly-developed brain and eye: help to avoid predation.
Cephalopoda: ADAPTATIONS
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Cephalopoda: Chambered Nautilus
Has a coiled external shell.
Shell has multiple compartments, some filled with gas to help with buoyancy.
Lives in deep, tropical waters.
Feeds during the night in shallower waters.
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You will be assigned 2 types of Cephalopods.
Go online and research the basic characteristics and life history of two chosen species.
Create a Valentine for each Cnidarian (you must choose a specific species).
Make it cheesy and creative.
Follow the rubric!
This assignment will be worth a DOUBLE CW GRADE!
Cnidarian Project
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Cephalopoda: Cuttlefish
Shell is internal – helps support the soft body.
Lives on the bottom of the ocean, preys on invertebrates in the sand.
Ten tentacles, 2 are very long.
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Breed in shallow water.
Separate sexes: internal fertilization; external development.
Male uses tentacle to deliver sperm to female (places it in mantle cavity).
Fertilized eggs are placed on rocks or algae: squid die after mating; octopus female cares for the eggs.
Cephalopoda: Reproduction
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https://www.youtube.com/watch?v=OueQ9kU36i0
Squid Dissection
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Squid Internal Anatomy
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