Annelida n n Annelid means little rings which

Annelida n n Annelid means little rings, which refer to body segments Earthworms and leeches · 15, 000 bilateral species of segmented worms · have true coelom · have external bristles called setae · some have fleshy protrusions called parapodia

3 classes based on number of setae 1. oligochaeta · earthworms · no parapodia · few bristles

3 classes based on number of setae 2. polychaeta · bristle worms · many parapodia · many bristles

3 classes based on number of setae 3. hirudinea · leeches · no parapodia · no bristles · have suckers

Class oligochaeta · live in soil or fresh water · most common is earthworm

Structure and movement · more than 100 segments · circular and longitudinal muscles line interior body wall · muscles contract, worm moves forward and setae grip the ground. Coelom is fluid filled and gives pressure on ground. This is locomotion

Feeding and digesting · soil is sucked in by muscular pharynx · passes through esophagus · enters crop which is a temporary storage area passes into gizzard which grinds the soil to release organic material · passes into intestines where nutrients are absorbed · anus is at the end of the digestive tract where waste materials pass out · worms are a burrowing animal and this helps the soil. This allows nutrients and oxygen to get in for plant roots, aerates the soil and loosens the soil.

Feeding and digesting 1. Intestines 2. Gizzard 3. Crop 4. Seminal vesicles 5. Seminal receptacles 6. Aortic arches 7. Esophagus 8. Pharynx 9. ganglia

Circulation · closed circulatory system · has dorsal and ventral blood vessel 1. dorsal blood vessel carries blood to anterior end 2. ventral blood vessel carries blood to posterior end · aortic arches *5 pairs of muscular tubes connecting the 2 vessels together *located in the anterior end *contractions cause blood to move

Circulation

Respiration and excretion · no special respiratory organs · oxygen and carbon dioxide diffuse through skin (moist skin) · nephridia are excretory organs. They are located in all segments but the first three and last one. These release excretions through ventral pores

Respiration and excretion

Neural control · have ganglia connected to ventral nerve cord · each segment has ganglia but anterior segment has a few ganglia fused into the cerebral ganglion. This is where most senses are sensed: light, touch, chemicals, moisture, temperature, and vibrations

Neural control

Reproduction · hermaphrodites · no self-fertilization · 2 worms come close together with ventral surfaces and anterior ends pointing in opposite direction · clitellum (thickened section of body) secretes mucus to hold worms together. · Each worm injects sperm into mucus. The sperm travels to seminal receptacle of other worm. A hard tube called chitin takes eggs to sperm and fertilization occurs in tube.

Reproduction

Earthworm review n n Read pp. 733 -736 p. 736 1 -6 p. 737 read bottom 37 -2 p. 738 2, 4 -6, 12 -15, 21 -24