Segmented Worms: Phylum AnnelidaSegmented Worms: Phylum Annelida EX:EX: EarthwormsEarthworms

A. General Characteristics:A. General Characteristics:1. Annelid- “little rings”1. Annelid- “little rings”2. Earthworms, blood-sucking leeches2. Earthworms, blood-sucking leeches3. true coelom: body cavity3. true coelom: body cavity4. body is divided into segments4. body is divided into segments5. organ systems are well developed5. organ systems are well developed6. have 6. have setaesetae: external bristles that help move and burrow into the dirt.: external bristles that help move and burrow into the dirt.

B. B. Digestive system/excretory systemsDigestive system/excretory systems1. mouth and anus1. mouth and anus2. feed on soil and organic matter2. feed on soil and organic matter3. how food moves through digestive system.3. how food moves through digestive system.

a. soil is sucked in by the a. soil is sucked in by the pharynxpharynx and through the and through the mouthmouth..b. it moves through the b. it moves through the esophagusesophagusc. into the c. into the cropcrop- storage area- storage aread. Then to the d. Then to the gizzardgizzard- grinds up food- grinds up foode. solid waste are excreted through the e. solid waste are excreted through the anusanusf. liquid waste are excreted through f. liquid waste are excreted through nephridianephridia

C. Respiratory systemC. Respiratory systema. earthworms do not have gills or lungsa. earthworms do not have gills or lungsb. gas exchange must occur- exchange of oxygen and carbon dioxide. b. gas exchange must occur- exchange of oxygen and carbon dioxide. c. skin must stay moist: c. skin must stay moist:

1. secrete mucous1. secrete mucous2. thin cuticle that holds moisture2. thin cuticle that holds moisture

d. If they do not stay moist, they will died. If they do not stay moist, they will dieD. Circulatory SystemD. Circulatory System

a. a. closed circulatory systemclosed circulatory system: runs through vessels: runs through vesselsb. blood travels from b. blood travels from anterior to posterioranterior to posterior end by end by ventral blood vesselventral blood vesselc. blood travels from c. blood travels from posterior to anteriorposterior to anterior end by a end by a dorsal blood vessel. dorsal blood vessel. d. d. Aortic Arches(Aortic Arches( 5 hearts) 5 hearts)

1. in the anterior end1. in the anterior end2. link the dorsal and ventral blood vessels.2. link the dorsal and ventral blood vessels.3. called 5 hearts because they contract rhythmically to help pump 3. called 5 hearts because they contract rhythmically to help pump

blood through the system. blood through the system. 4. smaller vessels branch into each segment of the body4. smaller vessels branch into each segment of the body

E. E. MovementMovementa. two types of musclesa. two types of muscles

1. 1. LongitudinalLongitudinal: Runs anterior to posterior. When they contract, : Runs anterior to posterior. When they contract, the worm the worm

becomes shorter. becomes shorter. 2. 2. CircularCircular: circles around the body of the worm. When they : circles around the body of the worm. When they

contract, the worm contract, the worm lengthens (becomes skinnier)lengthens (becomes skinnier)

F. ReproductionF. Reproductiona. Hermaphroditesa. Hermaphroditesb. Sexually:b. Sexually:

1. two earthworms join head to tail at the clitellum1. two earthworms join head to tail at the clitellum2. they exchange sperm2. they exchange sperm3. sperm is stored until eggs are ready to fertilize3. sperm is stored until eggs are ready to fertilize4. a mucous sheath is formed around the clitellum 4. a mucous sheath is formed around the clitellum 5. eggs and sperm are released into the sheath 5. eggs and sperm are released into the sheath

(cocoon)(cocoon)6. worm wiggles to slip the sheath off6. worm wiggles to slip the sheath off7. egg and sperm join during7. egg and sperm join during the wigglingthe wiggling8.8. fertilization occursfertilization occurs

                                           

                                Earthworm Cocoons

                               

                

Anterior end

Posterior end

Outside structure of an earthworm: Dorsal side (darker side)

About one third of the way down the earthworm (from the head) is the clitellum. The clitellum is a swelling of the skin and can only be seen in earthworms that are ready to reproduce. It may be white, orange-red or reddish-brown in colour. Earthworms are ready to mate when their clitellum is orange. Most of the material secreted to form earthworm cocoons is produced within the clitellum

Underside of Earthworm (Ventral)Underside of Earthworm (Ventral)

(Lighter side)(Lighter side)

Prostomium: Tongue like structure used to Sense things. It is used by the earthworm to “see” its environment - as earthworms have no eyes, ears, nose or hands, it depends on the prostomium and skin to help it feel its way through the soil.

Digestive System of Earthworm: pharynx, mouth, esophagus, crop, gizzard, intestine.

Respiratory System (red): 5 hearts, dorsal blood vessel, ventral blood vessel

Dorsal Blood Vessel

Ventral blood vessel Nervous system: Brain (ganglia), ventral nerve cord

Respiratory, digestive, and circulatory systems of an earthworm

Pharynx