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Biology 11
25.4 – Phylum Annelida
Body Structure of Segmented Worms
 Annelids undergo _________________ development.
 Include earthworms, marine worms, and parasitic leeches
 __________ and have a _____________
 Rigidity in annelid segments creates a _______________ skeleton that muscles can push
against.
 Segmentation also permits segments to move ____________ of each other and enables
a worm to survive damage.
 Segments can be _____________.
Feeding and Digestion
 Running through all earthworm ___________ from the mouth to the anus is the
digestive tract.
Circulation
 Most annelids have a ___________ circulatory system.
Respiration and Excretion
 Earthworms take in oxygen and give off carbon dioxide through
their __________ skin.
 Aquatic annelids have __________ for the exchange of gases in the water.
 Segmented worms have two _____________ in almost every segment.
Response to Stimuli
 The ___________ segments are modified for __________ the environment.
Movement
 The earthworm contracts ___________ muscles running around each segment.
 This ____________ the segment and causes the fluid in the coelom to press
____________like paste.
 The fluid pressure causes the segment to get _________ and ______________.
Biology 11
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The earthworm contracts the ___________ muscles that run the length of its body.
This causes the segment to _____________ and return to its original shape, pulling its
posterior end _______________ and resulting in movement.
Reproduction
 Reproduce both ___________ and ____________
 Sperm are passed between two worms near segments called the _____________.
 The clitellum produces a ____________from which the young earthworms hatch
Diversity of Annelids
 Annelida
 Typically live underground in
_______________ habitats.
 ___________ the soil as they feed off
of it.
 Earthworms and their relatives

Polychaeta
 Typically live in ______________
environments
 Bodies have _____________ for
swimming and crawling
 Filter feeders who trap food in
___________on their bodies.

Hirudinea
 Typically live in
___________environments
 Most are ______________
 Leeches have adapted chemicals to stop
_____________ of blood.