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Mollusks and Annelids
Mollusks Characteristics
Body Cavity:
Mollusks have a true ____________, (first group to have). The gut and other
internal organs are suspended from the body wall and cushioned by the
__________ within.
Symmetry: _______________
True coelom - diagram
Mollusks body plan
3 part body plan:
1. visceral mass – center section with ____________
2. Mantle – tissue fold that is outer layer and wraps around the
____________ mass like a cape
3. Foot – muscular regions, mainly _________________
Body plan diagram
More characteristics
Shell: 1 or 2 shells that serve as an ____________, composed of Calcium
Carbonate
Radula: all have except bivalves, ___________-like organ in mouth with
backward-curving teeth
Only coelomates ___________ segmented bodies
Internal anatomy of a mollusk – diagram
Organ system
____________– coelom is collection place waste, cilia pulls the fluid into
nephridia (tubular structures for recycling useful substances), wastes leave
through _________ the opens into the mantle
Circulation – most _____chambered heart, open circulatory (octopuses and
squids – closed)
Respiration – In water: most have __________ in the mantle cavity, freshwater
snails – _____________, Land have a primitive __________
Nephridium diagram
Organ system con’t
Reproduction:
-Most have distinct ___________ / females
-Some hermaphrodites
-Oysters ________________ sex
-Trochophore larvae
Trochophore larva – diagram
Gastropoda-c
Snails / slugs, sea hare Aplysia-g reaches 1 m.
Most gastropods have a ___________ shell
Foot for locomotion
Terrestrial secret ____________ from base of their foot
Pair of tentacles on head with eyes located at the _________.
Gastropods and food
Herbivore – scrape ____________
Sea slugs, whelks and oyster use radula to bore holes in shells of other mollusks
__________ shells the radula modified into poison- tipped harpoon.
Humans eat: land _________- Helix – g , marine – ___________
Gastropod diagram
Bivalvia-c
Most marine
_______-part hinged shell (valves – secreted by mantel), 2 thick ___________
muscles connect valves
_______ distinct head region or radula, nerve ganglion above foot (simple brain),
respond to light and touch
External fertilization, free-swimming trochophore larvae, mussels in pouch in
______
Bivalves and food
oysters / mussels human food
________ feeders: siphons (hollow _________) draws water in one side to go
over gills and out other side
Sticky mucus in gills – _______ food to which cilia direct to mouth (clams,
oysters and scallops)
Bivalve diagram
Pearls
Foreign ________ lodged between mantle and shell. Coats with thin sheets of
_________(mother of pearl). Also on insides of shells. Layers added until
completely enclosed
In fine pearls the nacre has tiny, overlapping mineral crystals that act like
__________, iridescence
Best from Pinctada – g
Pearl diagram
Cephalopods -c
Squids, octopuses, cuttlefish, nautiluses
Means “____________”, “foot”
Most no external shell (_____________ does)
Giant squid largest invertebrate at 20m (65 ft)
Large head attached to tentacles (divided foot), ___________ or hooks. Squids10, octopuses-8,nautilus – 80+ and has outer shell
Most ________________ of invertebrates, complex nervous system, brain –
discern shapes, eye with color vision
Cephalopods moving
Water in mantel cavity and out siphon – _________ propulsion
Dark fluid (___________) to murky up water for escape.
Cuttlefish ink is reddish brown (__________) used in paintings
Cuttlefish “bones” used for birds to get ____________
Active marine predator: eat mollusks, crustaceans and worms
Cephalopoda diagram
Annelids - p
1mm to 3m (10 ft)
Segmented – ring like structures along length of their body
________ – internal body walls separate the segments
Anterior has cerebral ganglion, nerve cord underside (___________ body
Coelom- large, fluid-filled, entirely in mesoderm
Closed circulatory
Respire through skin
_____________ – excretory structures
Annelids classified
Setae – external ________________ paired on each segment
____________ – fleshy appendages
Classification of the classes are based on the presence or lack of ____________
and ______________
Annelid diagram
Polychaeta - c
Marine worms, largest group, ________________ colors
______________ on each segment with setae on them, gas exchange due to
increase surface area
Burrowing, protective ____________ by harden secretions, tubeworms, feather
duster – lives with only head out of tube (filter feeder)
Nereis -g – free __________________ and strong jaws (predator)
Polychaeta example
Oligochaeta - c
Earthworms – Lumbricus terrestris
__________ parapodia and few setae on each segment
Head region: no eyes but light / touch /moisture organ
Respiratory exchange through _____________ (moist)
Eat __________. Moves through one-way gut. Pharynx-crop (storage chamber)
– gizzard (grinds soil) – intestines- anus and material out called ____________;
aerates the soil
Hermaphrodites
Oligochaeta example
Hydrostatic skeleton
Fluid in coelom creates it
Muscles that pull against:
-_________________ muscles wrap around the segment
-_________________ muscles span its length
When circular muscles contract – worm _____________, longitudinal – worm
________________ up
Hirudinea - c
_____________ – bloodsucking due to suckers at both ends of its body (aquatic,
terrestrial, some parasitic)
______________ setae and parapodia
Flattened body
Segments not separated internally
Used in old days for ______________
Used today in _____________ reattachment surgery (microsurgery) to suck out
accumulated blood, tissue remain healthy until new blood vessels can grow
Saliva is anticoagulants – prevent _________________ and enzymes that break
up blood clots.
Hirudinea example