Soft-bodied coelomates, multicellular, bilateral symmetry Divided into three parts: head-foot-...

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

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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

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