1. Phylum Annelida (Chapter 27.3)
Please set up your notebook for Cornell Notes

2. Annelids
Characteristics
Body divided into segments separated by walls called septa
Have a coelom  coelomates
Some worms have bristles called setae attached to each segment
Have mouth and anus, digestive tract
Triploblastic  three germ layers

3. Form and Function
Feeding and digestion
Filter feeders, predators, decomposers
Have a pharynx
Pharynx has jaws in carnivores
Pharynx covered in sticky mucus in decomposers
Pharynx pumps food and soil into esophagus
Crop – stores food
Gizzard – grinds food into smaller pieces
Food absorbed in intestines

4. Circulation
Annelids have a closed circulatory systems
Two major blood vessels
No heart – dorsal blood vessel contract and circulates blood
Respiration
Aquatic annelids breathe using gills feathery structures used to exchange gases underwater
Land dwelling annelids diffuse gases through moist skin

5. Excretion
Digestive waste passes out of the anus
Nitrogenous waste is excreted through the nephridia  organs that filter fluid in coelom
Response
Most annelids have a brain and several nerve cords
Marine annelids have many sensory adaptations
Sensory tentacles, chemical receptors, statocysts, eyes

6. Movement
Two major groups of muscles
Longitudinal  contract to make the worm shorter and fatter
Circular  contract to make worm longer and thinner
Marine annelids have paddle-like appendages called parapodia on each segment used for swimming and crawling

7. Reproduction
Most annelids reproduce sexually
Some have separate sexes, and external fertilization
Others are hermaphroditic but do not fertilize their own eggs
Two worms attach to each other, exchange sperm and store for later
When eggs are ready, the clitellum secretes a thick mucus ring where eggs and sperm are deposited
Ring slips off and provides a cocoon for developing larva
Some annelids reproduce asexually through budding

8. Classes of annelids
Class Oligochaeta
Stream-lined bodies with very few setae
Mostly live in soil and fresh water
Earthworms and tubifex worms

9. Class Hirudinea
External parasites that suck blood and body fluids
Leeches
Live in moist habitats in tropical countries
Have powerful suckers at both ends
Posterior  attachment
Anterior  Eating

10. Class Polychaeta
Marine annelids w/ paired, paddle-like appendages that have setae on the tip
Sandworms, blood worms
Live in cracks in coral reefs, in sand and mud and open water