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Soft-bodied coelomates, multicellular, bilateral symmetryDivided into three parts: • head-foot- muscular organ covered in cilia and rich in mucous
cells• visceral mass- it is the body cavity that holds the digestive,
excretory, and reproductive organs; includes gonads, the kidney, the heart
• mantle- folds arise from dorsal body wall and enclose a cavity between themselves and visceral mass
• mantle cavity acts as lung
Gills- specialized portions of mantle that consist of a system of filament as projections rich in blood vessels open circulatory system except cephalpods nephrida-tubular structures, remove nitrogenous waste outer surface of mantle secretes protective shell
Second most diverse phylumOver 110,000 species
Phylum: MolluscaClassesPolyplacophora- marine mollusks oval bodies, not segmentedEx: chitons
Gastropods- primarily marine, freshwater and terrestrial mollusks, typically live in hard shellEx: Snail and slugs
Bivalves- two lateral shells hinged dorsally, no distinct head area
Ex: oysters and clams
Freshwater clam
Cephalopods- active marine predators, well developed brains, intelligent invertebratesEx: octopuses and squids
• Heterotroph• Radula is used for feeding, it’s a rasping, tongue-like
organ, chitinous teeth in rows• Gastropods use radula to scrape algae and food
materials • Food is taken up by cells lining the digestive glands
arising from the stomach, and then is passed into the blood.
Uniqueness• Mollusks have unique structure because some contain
radula.
• Distinct male and female individual• Few bivalves and gastropods are hermaphroditic• Cross fertilization most common• Aquatic mollusks-external fertilization• Male and female release gametes in water and mix
fertilization occurs• Gastropods-internal fertilization- adaptation allows
gastropods to live on land
• Important source of food for humans • Economic significance-pearls are produced in oysters• Bivalve mollusks called shipworms burrow through
wood submerged in the sea damaging boats, docks, and pilings.
• Zebra mussel invaded North American ecosystems it affected aquatic ecosystems.
• Snail fever-schistosomiasis
• tube within a tube with internal digestive tract,• tube runs through mouth to anus suspended within the
coelom• hydrostatic skeleton-locomotion• Segmented, multicelluluar• Excretory system- ciliated funnel shaped nephridia• Digestive tract- pharynx, esophagus, crop, gizzard, and
intestine
• Repeated segments- excretory, locomotor organs repeated each segment
• Setae- bristles of chitin help anchor worm during locomotion
• Specialized segments• Closed circulatory system • Lack gills, lungs
Phylum: Annelida
Classes• Polychaeta-free living, well developed head with
specialized sense organs, parapodia ex: clamworms, marine worms, peacock worms
• Oligochaeta- fewer setae than polychaetes, no parapodia, no head region
• ex: earthworm
• heterotroph • Earthworms eat through soil and other organic
material by expanding strong pharynx• Gizzard grinds organic material
• polychaetes lack gonads, produce gametes directly from germ cells in lining of coelom or in septa
• external fertilization in water• Earthworms and leeches are hermaphroditic• Leeches- cross fertilization, unable to self fertilize
Uniqueness• Earthworms are hermaphroditic(male and female)
• Earthworms aerate and enrich the soil• Leeches are used to remove excess blood after certain
surgeries after they remove excess blood new capillaries form and tissues remain healthy
• Leeches were used hundreds of years in medicine to take blood out of patients whose diseases were mistakenly believed to be caused by excess blood
• Freshwater leeches live as external parasites and suck their blood
• Earthworms are a source of food for numerous animals, like birds, rats, and toads
• Predation: Ex: bird eats worm
(2002). Blue-ringed octopus. (2002). [Web Photo]. Retrieved from http://www.pbs.org/kcet/shapeoflife/animals/molluscs1.html Cortes, L. (Photographer). (n.d.). Common octopus. [Web Photo]. Retrieved from http://ocean.nationalgeographic.com/ocean/photos/unique-sea-creatures/Edwards, J. (Photographer). (n.d.). Retrieved from
http://animals.nationalgeographic.com/animals/invertebrates/earthworm/Edwards, J. (Photographer). (n.d.). Common earthworm. [Web Photo]. Retrieved from http://animals.nationalgeographic.com/animals/invertebrates/earthworm/(n.d.). Excretion and osmoregulation in earthworm. [Web Photo]. Retrieved from
http://images.tutorvista.com/content/excretion-and-osmoregulation/earthworm-cross-section.jpeg(1997). Freshwater clam. (1997). [Print Photo]. Retrieved from http://www.liveaquaria.com/product/prod_display.cfm?c=1075 1642&pcatid=1642(n.d.). Information and facts about snails. [Web Photo]. Retrieved from http://www.snail-world.com/ Onthank, K. (Photographer). (2011). Eyes of rock let chitons see predators. [Web Photo]. Retrieved from
http://m.today.duke.edu/2011/04/chiton.html
Raven, P., & Johnson, G. (2002). Biology. (Sixth ed., pp. 899-909). New York: McGraw-Hill.(n.d.). Retrieved from http://7salemanimalkingdom.wikispaces.com/file/view/T761279A.gif/33933193/T761279A. gifSkerry, B. (Photographer). (n.d.). Caribbean reef squid. [Web Photo]. Retrieved from http://ocean.nationalgeographic.com/ocean/photos/squid/(n.d.). The lumbricus rubellus genome project and annelid est database . [Web Photo]. Retrieved from http://xyala.cap.ed.ac.uk/Lumbribase/images/earthworm1.jpg