Mollusca - soft-bodied
- level of organization - organ systems
- body symmetry - bilateral symmetry
- alimentary structures - 2-hole tube
- triploblastic
- coelomate - contains fluid-filled space surrounded by mesoderm layer to hold organ systems
- coelom isolated to area around heart in mollusks
- not the same as digestive/mantle cavities
- mantle - specialized epidermal cells, can secrete shell
- visceral mass - organ systems, sensory structures
- open circulatory systems in all except Cephalopods
- gas exchange occurs in gills
- Class Polyplacophora - “many moving plates”
- uses radula (horny tongue) to scrape food from rocks
- dorsal shell divided into 8 plates
- Class Gastropoda - “stomach foot”
- single, coiled shell produced in snails
- no shells for slugs/nudibranchs
- uses radula
- Class Bivalvia - “two doors/valves”
- hinged shell for protection
- sessile filter feeders
- incurrent/excurrent siphon directs water through clam
- Class Cephalopoda - “head-foot”
- shell internalized or lost
- can alter shape/color for camouflage
- hardened beak for crushing prey
- tentacles w/ suckers to ensnare prey
- most intelligent/advanced of invertebrates
Annelida - “ringed/segmented”
- level of organization - organ systems
- body symmetry - bilateral symmetry
- alimentary structures - 2-hole tube
- triploblastic, coelomate
- segmentation - divided into parts separated by septa
- muscles can elongate/contract for locomotion
- parts specialized for certain tasks
- closed circulatory system
- setae - small bristle-like appendages
- no gills/lungs, oxygen absorbed through moist body surfaces (cutaneous respiration)
- mouth >> pharynx >> esophagus >> crop >> gizzard >> intestine
- can only reproduce through cross-fertilization, even though it’s hermaphroditic
- sperm exchanged through clitellum
- Class Polychaeta - “many setae”
- well defined heads
- can be venomous
- active predator/scavenger
- Class Oligochaeta - “few/small setae”
- earthworms, redworms, etc
- Class Hirudinea - leeches
- secretes hirudin as anticoagulant
- some live as ectoparasites
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