Phylum Annelida: Segmented Worms

Chapter 27~~~ IN 121

A. General Characteristics Phylum: Annelida1. 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 Parts1. 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

1. Prostonium (lip)

2. Mouth

3. Pharynx (the throat)

4. Esophagus

5. Crop

6. Gizzard

7. Intestine

8. 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

6. Medical Uses

a. Anesthetic

b. Increase circulation

c. Secretions act as anticoagulants during feedings

d. Reattachment of digits

e. Reduce swelling

f. Cosmetic surgery

Segmented Worm Quiz1. The term “annelid” means ___.

a. Round worm b. flat worm

2. Annelids have ___symmetry and ___ body openings.

a. 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.

b. Anesthetic b. toxin c. anticoagulant

5. True/False: Leeches serve a useful purpose to man.

Comparing Flatworms, Roundworms, and AnnelidsComparing Flatworms, Roundworms, and Annelids

CHARACTERISTIC

Shape

Segmentation

Body cavity

Digestion and excretion

Respiration

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

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

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

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

Section 27-3

Compare/Contrast Table

Comparing Flatworms, Roundworms, and AnnelidsComparing Flatworms, Roundworms, and Annelids

CHARACTERISTIC

Circulation

Response

Movement

Reproduction

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)

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)

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)

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)

Section 27-3Compare/Contrast Table continued