1. Phylum Annelida: Segmented Worms
Chapter 27~~~ IN 121

2. A. General Characteristics Phylum: Annelida
Annelid: means“tiny rings”
2. Class: Oligochaeta
3. Examples: bristleworms, earthworms, leeches.
4. Bilateral animals w/ 2 body openings (mouth and anus).
5. Segmented Body
6. Live soil or freshwater
7. Nocturnal burrowing worm
8. Feeds on dirt filtering out organic matter
9. Beneficial to the soil: aeration (opening up soil to allow air to circulate better), fertilization
10. Respiration: oxygen diffuses across moist skin
11. Sexual Reproduction- hermaphrodites (Earthworms & Leeches)
12. Closed circulatory system: blood contained within vessels,
13. Well Developed Nervous System

3. B. Earthworm Parts 1. Crop: temporary storage sac after mouth
2. Gizzard: sac w/muscular walls to grind soil
3. Intestine: long intestine stretches length of body to aid in digestion of soil
4. Ganglion: brain-like organ
5. Aortic Arches: Heart of worm; really 5 enlarged
blood vessels.

4. B. Earthworm Parts
6. Anus: wastes are removed
7. setae: bristles used for movement located on ventral side
8. Clittelum: enlarged reproductive segment, secretes mucus which helps hold worms together during reproduction

5. Pathway of Digestion in an Earthworm
Prostonium (lip)
Mouth
Pharynx (the throat)
Esophagus
Crop
Gizzard
Intestine
Anus

6. C. Leeches: 1. Class: Hirudinea 2. Parasitic segmented worm
3. Most live in fresh water
4. Have no bristles for movement, move w/muscular contractions
5. Suckers at each end of body
Medical Uses
Anesthetic
Increase circulation
Secretions act as anticoagulants during feedings
Reattachment of digits
Reduce swelling
Cosmetic surgery

8. Segmented Worm Quiz The term “annelid” means ___.
Round worm b. flat worm c. segmented worm.
Annelids have ___symmetry and ___ body openings.
Radial, 1 c. bilateral, 1
b. radial, 2 d. bilateral, 2
3. True/False: Earthworms have 5 true hearts.
4. To keep you from feeling it, the leech secretes an ___ when it bites into you to feed.
Anesthetic b. toxin c. anticoagulant
5. True/False: Leeches serve a useful purpose to man.

9. Compare/Contrast Table
Section 27-3
Comparing Flatworms, Roundworms, and Annelids
CHARACTERISTIC
Shape
Segmentation
Body cavity
Digestion and excretion
Respiration
FLATWORMS
Flattened No
Acoelomate
Gastrovascular cavity with one opening only; flame cells remove metabolic wastes
Through skin; no respiratory organs
ROUNDWORMS
Cylindrical with tapering ends No
Pseudocoelomate
Tube-within-a-tube digestive tract; opening at each end; metabolic wastes excreted through body wall
Through skin; no respiratory organs
ANNELIDS
Cylindrical with tapering ends
Yes
Coelomate
Tube-within-a-tube digestive tract; opening at each end; nephridia remove metabolic wastes
Through skin; aquatic annelids breathe through gills

10. Compare/Contrast Table continued
Section 27-3
Comparing Flatworms, Roundworms, and Annelids
CHARACTERISTIC
Circulation
Response
Movement
Reproduction
FLATWORMS
No heart, blood vessels, or blood
Simple brain; nerve cords run length of body; eyespot and other specialized cells that detect stimuli
Gliding, twisting, and turning
Sexual (hermaphrodites); asexual (fission)
ROUNDWORMS
No heart, blood vessels, or blood
Several ganglia in head region; nerve cords run length of body; several types of sense organs
Thrashing
Sexual (primary males and females)
ANNELIDS
Blood circulated through blood vessels in closed circulatory system
Well-developed nervous system with brain and several nerve cords; many sense organs
Forward peristaltic movement
Sexual (some are hermaphrodites; some have separate sexes)