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Phylum Annelida : Segmented Worms Chapter 27~~~ IN 121. 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
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Phylum Annelida: Segmented Worms Chapter 27~~~ IN 121
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
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.
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
Pathway of Digestion in an Earthworm • Prostonium (lip) • Mouth • Pharynx (the throat) • Esophagus • Crop • Gizzard • Intestine • Anus
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
Segmented Worm Quiz • The term “annelid” means ___. • Round worm b. flat 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.
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
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)