Phylum Annelida: Segmented Worms Chapter 27~~~ IN 121
Feb 23, 2016
Phylum Annelida: Segmented WormsChapter 27~~~ IN 121
A. General Characteristics Phylum: Annelida1. Annelid: means“tiny rings” 2. Class: Oligochaeta3. Examples: bristleworms, earthworms, leeches.4. Bilateral animals w/ 2 body openings (mouth and anus). 5. Segmented Body6. Live soil or freshwater7. Nocturnal burrowing worm 8. Feeds on dirt filtering out organic matter9. Beneficial to the soil: aeration (opening up soil to allow air to
circulate better), fertilization10. Respiration: oxygen diffuses across moist skin11. Sexual Reproduction- hermaphrodites (Earthworms & Leeches)12. Closed circulatory system: blood contained within vessels, 13. Well Developed Nervous System
B. Earthworm Parts1. Crop: temporary storage sac after mouth2. Gizzard: sac w/muscular walls to grind soil3. Intestine: long intestine stretches length of body
to aid in digestion of soil4. Ganglion: brain-like organ5. Aortic Arches: Heart of worm; really 5 enlarged
blood vessels.
B. Earthworm Parts 6. Anus: wastes are removed7. setae: bristles used for movement located on ventral side 8. Clittelum: enlarged reproductive segment, secretes mucus which helps hold worms together during reproduction
Pathway of Digestion in an Earthworm
1. Prostonium (lip)2. Mouth3. Pharynx (the throat)4. Esophagus5. Crop6. Gizzard7. Intestine8. Anus
C. Leeches:1. Class: Hirudinea2. Parasitic segmented worm3. Most live in fresh water4. Have no bristles for movement, move
w/muscular contractions5. Suckers at each end of body6. Medical Uses
a. Anesthetic b. Increase circulationc. Secretions act as anticoagulants during
feedingsd. Reattachment of digitse. Reduce swellingf. Cosmetic surgery
Segmented Worm Quiz1. The term “annelid” means ___.a. Round worm b. flat worm2. Annelids have ___symmetry and ___ body openings.a. Radial, 1 c. bilateral, 1 b. radial, 2 d. bilateral, 23. 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.b. Anesthetic b. toxin c. anticoagulant5. True/False: Leeches serve a useful purpose to man.
Comparing Flatworms, Roundworms, and Annelids
CHARACTERISTICShape
SegmentationBody cavityDigestion and excretion
Respiration
FLATWORMSFlattened
No
Acoelomate
Gastrovascular cavity with one opening only; flame cells remove metabolic wastes
Through skin; no respiratory organs
ROUNDWORMSCylindrical 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
ANNELIDSCylindrical 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
Section 27-3
Compare/Contrast Table
Comparing Flatworms, Roundworms, and Annelids
CHARACTERISTICCirculation
Response
Movement
Reproduction
FLATWORMSNo 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)
ROUNDWORMSNo 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)
ANNELIDSBlood 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)
Section 27-3Compare/Contrast Table continued