Transcript Excretion and osmoregulation in earthworm

Soft-bodied
coelomates, multicellular, bilateral symmetry
Divided 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
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Second
most diverse phylum
Over 110,000 species
Phylum: Mollusca
Classes
Polyplacophora- marine mollusks oval bodies, not segmented
Ex: chitons
Gastropods- primarily marine, freshwater and
terrestrial mollusks, typically live in hard shell
Ex: 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 invertebrates
Ex: octopuses and squids
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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
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Mollusks have unique structure because some contain
radula.
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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
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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
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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
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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
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Oligochaeta- fewer setae than polychaetes, no
parapodia, no head region
ex: earthworm
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heterotroph
Earthworms eat through soil and other organic
material by expanding strong pharynx
• Gizzard grinds organic material
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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
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Earthworms are hermaphroditic(male and female)
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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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