Annelida

Annelida 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 vessel1. dorsal blood vessel carries blood to anterior end2. 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 Read pp. 733-736 p.736 1-6 p.737 read bottom 37-2 p.738 2, 4-6, 12-15, 21-24