1. Phylum Annelida
The Segmented Worms

2. Phylum Level Characteristics
round
segmented (repeated body units containing similar structures)
bilateral symmetry, hydrostatic skeleton
complete digestive system
Eg. earthworms, leeches

3. Coelom -coelem forms from mesoderm
Creates space for the organs to grow and move
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4. Digestive System specialized areas/organs present: crop: stores food
gizzard: grinds food
pharynx: connects mouth with
digestive tract (gut)
Intestine: where nutrients
are absorbed

5. Respiratory System Aquatic annelids often breathe through gills
Other annelids take in oxygen and expel carbon dioxide through their skin
Skin must be moist for gas exchange to be possible
If worms dry out they suffocate and DIE!!

6. Circulatory System closed system
Typically, 2 blood vessels run length of body
Dorsal: blood moves towards head
Ventral: blood moves towards tail
necessary to provide glucose and oxygen to all cells of a fairly active animal

7. Excretory System Solid wastes pass out through anus
Metabolic wastes excreted by nephridia (like small kidneys) in each segment

8. Nervous System Brain sits at front of body
Ventral nerve cord runs entire length of worm
Many different types of sense organs depending on species

9. Movement 2 groups of muscles:
1. longitudinal-makes worm short and then long
2. lateral, circular-makes worm fat then thin
Setae- Hairlike anchors

10. Movement

11. Reproduction A few reproduce asexually by budding
Most reproduce sexually
Some species have separate sexes and external fertilization
Coordinate the release of eggs and sperm to increase the chances of successful fertilization
Done by aquatic annelids

12. Reproduction Earthworms and leeches are hermaphrodites:
1. the two worms attach themselves to each other
2. worms exchange sperm and it is stored
3. sperm fertilizes eggs internally in clitellum (mucous ring)
4. clitellum slips off worm’s body into soil (holding fertilized eggs) and becomes a cocoon